Research ArticlePassive and Active Restoration Strategies toActivate Soil Biogeochemical Nutrient Cycles ina Degraded Tropical Dry Land
Manuel F Restrepo Claudia P Florez Nelson W Osorio and Juan D Leoacuten
Universidad Nacional de Colombia Calle 59A No 63-20 Oficina 14-225 050034 Medellın Colombia
Correspondence should be addressed to Juan D Leon jdleonunaleduco
Received 30 April 2013 Accepted 6 June 2013
Academic Editors J A Entry and D Lin
Copyright copy 2013 Manuel F Restrepo et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited
The potential use of two restoration strategies to activate biogeochemical nutrient cycles in degraded soils in Colombia was studiedThe activemodel was represented by forest plantations of neem (Azadirachta indica) (FPN) while the passivemodel by successionalpatches of native plant specieswas dominated bymosquero (Croton leptostachyus) (SPM) In the field plots fine-litter traps and litter-bags were established samples of standing litter and surface soil samples (0ndash10 cm) were collected for chemical analyses during ayearThe results indicated that the annual contributions of fine litterfall in FPN and SPMwere 5575 and 9022 kg haminus1 respectivelyThe annual constant of decomposition of fine litter (k) was 158 for neem and 340 for mosquero Consequently the annual realreturns of organic material and carbon into the soil from the leaf litterfall decomposition were 146 and 36 kg haminus1 yrminus1 for FPN and462 and 111 kg haminus1 yrminus1 for SPM respectively Although both strategies showed potential to activate soil biogeochemical cycles withrespect to control sites (without vegetation) the superiority of the passive strategy to supply fine litter and improve soil propertieswas reflected in higher values of soil organic matter content and cation exchange capacity
1 Introduction
Land degradation in arid and semiarid lands increases asa result of soil misuse or mismanagement which togetherwith climatic variations may promote desertification andreduces soil productivity [1 2] In Colombia 789 of drylands show some degree of desertification mainly due tosoil erosion by overgrazing and soil salinity [3] Passiveand active restoration strategies have been proposed torestore the functioning of ecological processes [4] Passiverestoration strategies implyminimal human intervention andare based on natural succession process and in this waythe restorer has a passive role regarding the process On theother hand active restoration strategies include planting treesat high density and their respective management [5] thisstrategy implies a more active role of the restorer Althoughpassive restoration strategies are simple inexpensive andbased on natural regeneration processes they are not alwayssuccessful [6 7] Alternatively active restoration strategiesaccelerate the restoration of ecosystem functioning through
the activation of soil biogeochemical cycling of nutrients andcarbon sequestration [4]
The hypothesis of this study is that the activation of soilbiogeochemical nutrient cycles and soil quality improvementof degraded dry land depend on the strategy of restoration(active and passive) Thus the objective of this study wasto evaluate the potential use of both active and passivestrategies to restore soil biogeochemical nutrient cycles infine litterfall and soil quality in tropical degraded dry landsby overgrazing The active restoration strategy consisted ofa plantation of neem (Azadirachta indica) established sixyears ago for restoration purposes in soils severely erodedThe passive restoration strategy consisted of six-year-oldsuccessional patches dominated by native species wheremosquero (Croton leptostachyus) is the most abundant plantspecies that grow in the same eroded soils To this purposewe characterized several processes related to fine litterfalldynamics that control the flow of organic matter and nutri-ents and evaluated some soil physic-chemical parameters
2 ISRN Soil Science
Table 1 Mean values of structural parameters of the successionalpatches of mosquero (SPM) and forest plantations of neem (FPN)studied inAntioquia (Colombia) standard deviation in parentheses
mean square diameter119867 height119866 stand basal area
2 Material and Methods
21 Research Study Area This study was conducted in SantaFe de Antioquia northeastern Colombia (6∘541015840N 75∘811015840W560m of altitude)The annual average temperature sunlightprecipitation and evaporation of the region are 266∘C2172 h 1034mm and 1637mm respectively characterized bya pronounced annual water deficit derived from the Precip-itationEvaporation ratio of 063 The landscape consists ofhills with a low to medium slope formed from sedimentsfrom the TertiaryThe soils are alkaline and classified as TypicUstorthents (USDA soil taxonomy) the most dominant soiluse is grassland and unfortunately it is degraded by over-grazing The neem plantations studied here (active strategy)were established in 2004 on hillsides severely eroded byovergrazing since then forestry management practices havenot been carried out In the middle of these plantations havegrown natural successional patches (passive strategy) whichare constituted by native plant species heavily dominated bymosquero
22 Field and Laboratory Research Methods To evaluate thebiogeochemical cycle processes we established 20 circularplots of 250-m2 in forest plantations (FPN) and 13 similarplots in successional patches (SPM) (Table 1) In each plotthree circular litter traps (fine netting of 05-m2) were placed1-m above the soil surface Every 15 days for 1 year wecollected the litter material in each plot it means 60 samplesin FPN and 39 samples in SPM per sampling time
The litterfall was separated in the following fractions (a)neem leaves (NL) (b) mosquero leaves (ML) (c) leaves fromother species (OL) (d) wood material (WM) from branchesof lt2-cm diameter and small bark pieces (e) reproductivematerial (RM) and (f) other materials (OM) The dividedmaterial was oven dried at 65∘C and weighedThe samples ofNL andMLwere then separately combined and homogenizedfor every two 15-day periods (1 month) and a subsample wastaken for chemical analysis At the end of the year samplesfrom the accumulated litterfall layer or standing litter layeron the soil of the plantations and successional patches (a50 times 50 cm sample per plot) were collected Each samplewas separated in the same fractions than fine litterfall Eachfraction was dried at 65∘C until reaching constantmass (72 h)and weighed A composite and homogenized sample fromeach fraction was prepared for chemical analysis
The decomposition of neem and mosquero leaf litter wasstudied by installing 18 litter-bags (20 times 20 cm 2mm pores)with 3 g of senescent dry leaves per plant species Threelitter-bagswere randomly retrievedmonthlyThe residual leafmaterial was air-dried cleaned with a brush to remove soilparticles dried at 65∘C and weighed and named ldquoresidualdry matterrdquo (RDM) The samples from the three collectedlitter-bags in plantations and successional patches were thenseparately combined and homogenized for chemical analysisAdditionally in each plot of successional patches and forestplantations surface soil samples (0ndash10 cm depth) were col-lected Soil samples were also collected from 13 control siteswhere therewas not vegetation soil samples were transportedto laboratory for physical and chemical analyses
23 Physical and Chemical Analyses Leaf nutrient contentswere analyzed by different methods carbon (C) by theWalkley and Black method nitrogen (N) by the Kjeldahlmethod phosphorus (P) by the molybdate-blue methodcalcium (Ca)magnesium (Mg) and potassium (K) by atomicabsorption spectroscopy
In soil samples the methods used were pH (1 2 water)total N (Nt) (Kjeldahl method) available P (Bray-Kurtzrsquosmethod) exchangeable Ca Mg and K (1M ammoniumacetate atomic absorption spectroscopy) We also deter-mined soil bulk density (BD) and aggregate stability (AS)(Yoder method) Details about soil and plant analysis meth-ods are available in Westerman [8]
24 Statistical Analysis andCalculations Therate of potentialnutrient return (PNR) by the leaf litterfall was calculatedas the product of the nutrient concentration and the drymass of the leaf litterfall The retention of nutrients in thestanding litter (RNSL) was obtained by multiplying the dryweight of the leaves present in the standing litter and theirrespective concentrationWe calculated nutrient release fromthe decomposition coefficient 119896
119895
as proposed by Jenny etal [9] [119896
119895
= PNR(PNR + RNS)] The mean residencetime (MRT) of litterfall and nutrients was calculated as theinverse of 119896
119895
The real rate of nutrient return (RNR) from theleaf litterfall was calculated as the product of PNR and thecorresponding 119896
119895
coefficient [10]The weight loss in the litter-bags was expressed by a
simple exponential model [11]
119883119905
1198830
= 119890minus119896119905
(1)
where 119883119905
is the weight of the remaining material at moment119905 1198830
is the weight of the initial dry material 119890 is the basisof natural logarithm and 119896 is the decomposition rate Thetime required to obtain losses of 50 and 99 of the drymaterial was calculated as 119905
50
= minus0693119896 and 11990599
= minus4605119896respectively
Regression models were fitted using nonlinear regressionfor the weight loss of leaf material deposited in the litter-bagsLinear coefficient of determination (1198772) the Durbin-Watson(D-W) coefficient and the sum of the squares of the errorwere employed to select the models Correlation analyses
ISRN Soil Science 3
Table 2 Mean values of fractions for fine litter production (FLP) (kg haminus1 yrminus1) and standing litter (SL) (kg haminus1) in successional patches (SP)and forest plantations (FP) Standard deviation is in parentheses ML and NL leaf litter of mosquero and neem in their respective ecosystemOL other leaves RM reproductive material WM woody material OR other rests unidentified
FractionFLP SL
(kg haminus1 per two weeks) (kg haminus1 yrminus1) (kg haminus1 yrminus1)SPM FPN 119905 value SPM FPN SPM FPN 119905 value
decomposition time for half of the leaf litter 119905099
decomposition time for 99of the leaf litter 119896 yearly decomposition rate1198772 coefficient of determinationSSR sum of squared error D-W Durbin-Watson statistics
(r-Pearson 119875 le 005) were also used to determine associ-ations between weight loss rates and precipitation Becauselitter data were normally distributed a 119905-test was used todetermine the differences in fine litter production standinglitter and potential nutrient return between SPM and FPNTo compare soil parameters between control sites and bothrestoration strategies the Mann-Whitney (Wilcoxon) com-parison test (119875 le 005) was employed since these data werenot normally distributed The analyses were performed withStatgraphics Centurion XV (StatPoint Technologies Inc)
3 Results and Discussion
31 Fine Litter Production Accumulation and DecompositionThe results of this study clearly showed that there were sig-nificant differences between the active and passive strategiescharacterized here to activate soil biogeochemical nutrientcycles in tropical dry lands The annual production of leaflitter and total fine litter per unit area was 26-times and16-times higher in SPM than in FPN (Table 2) The higherfine litter production found in SPM represents a greaterpotential return of organic matter to these degraded soilsthan that of FPN The clear dominance of the leaf fractionin fine litter found in both types of ecosystems has beenreported in other studies [12]This also determines a potentialsource of nutrients for soil recovery because the higherdecomposition rate of this fraction represents a faster nutrientreturn path [13] By comparing the fine litterfall values withother studies the FPN were lower than those of tropicallowland forest plantations with ca of 5ndash10Mg haminus1 yminus1 [14ndash16]The fine litterfall values found in the SPM coincided withother tropical dry successional forests (03 to 42Mg haminus1 yminus1)as reported by Descheemaeker et al [17]
0
02
04
06
08
1
0 50 100 150 200 250
RDM
(ggminus
1
)
Time (days)
NeemMosquero
Figure 1 Residual dry matter (RDM) from leaf litter of neem (Aindica) and mosquero (C leptostachyus) Each point represents theaverage of three litter-bagsThe bars indicate the standard deviation
In the results we saw a contradiction about which typeof leaf litter decays faster The constant of decomposition(119896) showed that mosquero leaves are decomposed fasterthan neem leaves In fact it was noteworthy that the 119896constant of mosquero (34) was more than twice that ofneem (16) and the models predicted that the estimatedtime for 99 decomposition of leaf litter is 14 yr and 29 yrrespectively (Table 3) Furthermore at the end of the litter-bags experiment the RDM was 9 and 26 for mosqueroand neem respectively (Figure 1) However if we considerthe changes in the participation of neem andmosquero leavescollected in the litterfall traps (32 and 53 resp) with respect
4 ISRN Soil Science
Table 4 Meanmonthly values (plusmnSD) for leaf litter nutrient concentration (LLC ) and potential nutrient return (PNR kg haminus1) via leaf litterin successional patches of mosquero (SPM) and forest plantations of neem (FPN) studied Coefficient of variation () in parentheses
Nutrienta LLC () PNR (kg haminus1)119905 value 119890-value
119899SPM FPN SPM FPN
N 108 plusmn 013(119)
129 plusmn 031(242)
044 plusmn 035(789)
020 plusmn 018(1144) 2105 0047lowast 12
P 005 plusmn 001(156)
003 plusmn 001(190)
002 plusmn 002(792)
0005 plusmn 0004(867) 3052 0006lowastlowast 12
Ca 175 plusmn 033(189)
216 plusmn 065(301)
076 plusmn 060(797)
039 plusmn 044(820) 1721 0099NS 12
Mg 059 plusmn 008(139)
046 plusmn 006(139)
025 plusmn 021(834)
007 plusmn 006(645) 2829 0010lowastlowast 12
K 028 plusmn 013(449)
029 plusmn 014(493)
009 plusmn 008(802)
004 plusmn 003(890) 2226 0036lowast 12
aAnalytical methods in Westerman [8] lowast lowastlowastDenote significant differences between means of PNR at P values le 005 and le 001 respectively (119905-test)
to their participation in the standing litter (SL) (16 and 64Table 2) this suggests that neem leaves decomposed faster Itis necessary to consider that the neem leaves are fragile andcan be easily fragmented and for this reason they can be partof the OR fraction (plant remains unidentified) Thus theOR fraction (ORtotal) was only 2 in the fine litter (FLP)collected in the traps while this was 19 in the standinglitter (SL) Consequently we accepted that the k is a betterindicator and mosquero leaves decay faster In the litter-bagsexperiment the RDM of mosquero was only 9 which islower than that of neem 26 Also in the field the SL of FPNis higher suggesting that the decomposition of neem leavesis slower and for that reason they tend to accumulate on thesoil surface It has been reported that forest plantations withexotic species usually generate significant accumulations oflitter on the ground [18ndash20] Despite this accumulation thevalues found in the SL are relatively low in comparison tothose reported by other authors [10 20 21] Perhaps thisis a result of the young age of these forest plantations lackof canopy closure and low fine litterfall The 119896 values ofmosquero litter are comparable to those reported in tropicalarid ecosystems by several authors [15 22 23]
The high rate of decomposition of organic debris in SPMand therefore their low residence time are aspects of specialsignificance to the reactivation of biogeochemical nutrientcycle in these degraded soils [24] The inverse relationshipbetween the RDM in the litter-bags and the precipitation inSPM (r-Pearson = minus059 119875 lt 005) indicates the favorableeffect of the precipitation as a source of moisture for thedecomposer microorganisms perhaps this was not observedin the FPN because of the limitations of degrader microbes todecompose nonnative leaf material
32 Return Accumulation and Release of Nutrients In bothSPM and FPN nutrient concentrations in the leaf litter (LLC)followed the sequence Ca gt N gt Mg gt K gt P (Table 4)with the highest temporal variability for K The highconcentrations of Ca and Mg in the leaf litter found in thisstudy (175 and 216) differ from those found in other
tropical dry lowland forests [23] likely due to the high soilavailability of both nutrients (Table 6) By contrast the lowconcentration of K in the leaf litter (028ndash029) is near thelowest end of the pantropical interval (027 plusmn 011) [25]despite the availability of this nutrient in the soil Likely thelow soil CaMg ratio lt1 caused an abnormally high Mg plantuptake and altered the K uptake [26] In both ecosystemsthe most restrictive nutrient was P likely as a result of itsextreme scarcity in the soil (Table 6) which was reflected inthe high values of the leaf litter NP ratio (FPN 43 SPM 20)[10] These values of the NP ratio are much higher than thecritical value of 119 suggested by [27]
The potential nutrient return (PNR) through leaf litterfollowed the same sequence of concentrations (Table 4) andwas significantly higher in SPM because of the higher leaflitter production than in the FPN Furthermore the retentionof nutrients in the standing litter (RNSL) was higher inSPM which represents an important source of energy forthe micro- and mesofauna whose participation is a keyfunctional aspect to reactivate the biogeochemical cycling inthese degraded soils [28]
The real nutrient return (RNR) via leaf litter was higher inSPM for all nutrients (Table 5) This situation was primarilydetermined by the higher production of this fraction (ML)despite the fact that in FPN the 119870
119895
for some elements (C Pand K) was higher or similar (N) to those obtained in SPMThe low RNR of P also reflected the restrictive nature of thisnutrient for the productivity of both ecosystems [10]
In terms of the return and incorporation of organicmatter and C into the soil by leaf decomposition in theSL the superiority of SPM was notorious (Table 5) Thusthe real return of C (ML) in SPM was more than twicehigher than in the FPN (NL) In fact the highest rate of leaflitter decomposition of mosquero (higher values 119870
119895
and 119896)coincided with the highest contents of soil organic matter inSPM (Table 6)The times needed to achieve a decompositiondegree of 99 of leaves (14 yr for mosquero and 29 yr forneem) were close to those obtained from the inverse 119870
119895
inthe leaves of the SL (15 and 20 years resp)
ISRN Soil Science 5
Table 5 Indexes calculated for return retention and release of nutrients via leaf litter in successional patches of mosquero (SPM) and forestplantations of neem (FPN) (kg haminus1 yrminus1)
Table 6 Mean values (plusmnSD) for some soil parameters (0ndash10 cm) in successional patches of mosquero (SPM) forest plantations of neem(FPN) and control sites without vegetation studied in Santafe de Antioquia (Colombia)
AE () 728 plusmn 106 685 plusmn 129 094 801 plusmn 95 110aAnalytical methods available in Westerman [8]PCI parameter change index (FPNcontrol or SPMcontrol) SOM soil organic matter ECEC effective cation exchange capacity BD bulk density ASaggregate stability lowastIndicates significant difference with control sites (Mann-Whitney P le 005)
N and P were released more slowly (lower values of119896119895
) than other nutrients and they are expected to remainlonger in the above ground leaf litter as indicated by MRTvalues (Table 5) P was released faster in FPN (119870
119895
= 068MRT = 147 years) while N was released at similar rates inboth ecosystems (119870
119895
= 057 MRT = 176 years) In bothecosystems Ca had the highest release The time necessaryfor the effective release of all elements considered in bothecosystems was 11ndash181 years
33 Soil Reclamation Soils of both SPM and FPN showedchanges of some properties with respect to soil of control sites(without vegetation) (Table 6) In SPM significant increaseswere detected with respect to the control sites on parameterssuch as soil organic matter the content (SOM) exchange-able Mg and Ca and effective cation exchange capacity(ECEC)On the other hand in FPNwere observed significantincreases in SOM totalN (Nt) available-P and exchangeable-K and significant reduction in bulk density (BD)
Despite their short period of time for both strategiesthe contributions of fine litter and its decomposition haveimproved various soil properties of these degraded landsThesharp increases of SOM observed (compared to control sites)also increased soil moisture retention capacity and soil cationexchange key aspects in the reclamation of soils of degradeddry land Although FPN showed a significant increase of P
its very low concentration in the soil determined a severeconstraint on ecosystem primary productivity
4 Conclusions
From the perspective of land restoration both modelsshowed different advantages The passive model representedby the SPM showed a higher dynamics in the reactivation ofsoil biogeochemical cycles It is expected that as the succes-sional process continues the consequently greater complexityof the ecosystem will lead to an effective improvement notonly on the soil but also on ecosystem functions On theother hand the active model represented by the FPN showedsignificant improvements in soil parameters even thoughthe returns of litter and nutrients were lower Likely thissituation is the result of differences in litter contributionswhose potential effect on soil rehabilitation has not beenfully evaluated These are issues to consider in selecting arestoration model and the degree and speed expected ofthe degradation process Thus an active model should beconsideredwhen the rate of degradation of the area of interestis high because the planted species can be established quicklyand create better conditions for a more diverse biologicalcommunity as pointed by [5] When the state and rate ofdegradation are not severe themost appropriatemodelmightbe the passive restoration allowing the ecosystem a natural
6 ISRN Soil Science
recover [29] which had advantages from ecological andeconomic perspectives
Acknowledgments
The authors thank the Direction of Research of the Universi-dadNacional de Colombia for financial support of the ProjectldquoRestoration of lands in a process of desertificationwith neemplantations (Azadirachta indica) in Western Antioquiardquo JuanD Leon was supported by Convocatoria Nacional de Investi-gacion y de Creacion Artıstica de la Universidad Nacional deColombia 2010ndash2012 They also thank the BiogeochemistryLaboratory of the Universidad Nacional de Colombia atMedellin campus The authors are grateful to A N Marın LF Osorio J C Guingue G E Mazo and N Alvarez for theirtechnical collaboration
References
[1] Y Zha and J Gao ldquoCharacteristics of desertification and itsrehabilitation in Chinardquo Journal of Arid Environments vol 37no 3 pp 419ndash432 1997
[2] J F Reynolds and D M Stafford Smith Global DesertificationDo Humans Cause Deserts Vol 88 University Press BerlinGermany 2002
[3] Plan de Accion Nacional de Lucha Contra la Desertificacion y laSequıa en Colombia (PAN) Ministerio de Ambiente Vivienday Desarrollo Territorial Bogota Colombia 2004
[4] D Celentano R A Zahawi B Finegan R Ostertag R J Coleand K D Holl ldquoLitterfall dynamics under different tropicalforest restoration strategies in Costa Ricardquo Biotropica vol 43no 3 pp 279ndash287 2011
[5] S D Reay and D A Norton ldquoAssessing the success of restora-tion plantings in a temperate New Zealand forestrdquo RestorationEcology vol 7 no 3 pp 298ndash308 1999
[6] K D Holl ldquoTropical moist forest restorationrdquo in Handbook ofEcological Restoration M R Perrow and A J Davy Eds pp539ndash558 Cambridge University Press Cambridge UK 2002
[7] J Schrautzer A Rinker K Jensen F Muller P Schwartzeand C Dier Ben ldquoSuccession and restoration of drained fensperspectives from northwestern Europerdquo in Linking Restorationand Ecological Succession L R Walker J Walker and R JHobbs Eds pp 90ndash120 Springer New York NY USA 2007
[8] R L Westerman Soil Testing and Plant Analysis Soil ScienceSociety of America Madison Wis USA 1990
[9] H Jenny S Gessel and F Bingham ldquoComparative study ofdecomposition of organic matter in temperate and tropicalregionsrdquo Soil Science vol 68 pp 419ndash432 1949
[10] J D Leon M I Gonzalez and J F Gallardo ldquoCiclos bio-geoquımicos en bosques naturales y plantaciones de conıferasen ecosistemas de alta montana de Colombiardquo Revista BiologıaTropical vol 59 pp 1883ndash1894 2011
[11] J Olson ldquoEnergy storage and balance of producers and decom-poser in ecological systemsrdquo Ecology vol 44 pp 322ndash331 1963
[12] V Meentemeyer E O Box and R Thompson ldquoWorld patternsand amounts of terrestrial plant litter productionrdquo Biosciencevol 32 pp 125ndash128 1982
[13] C Strojan F Turner and R Castetter ldquoLitter fall from shrubs inthe northernMojave desertrdquo Ecology vol 60 pp 891ndash900 1979
[14] J A Parrotta ldquoProductivity nutrient cycling and succession insingle- and mixed-species plantations of Casuarina equisetifo-lia Eucalyptus robusta and Leucaena leucocephala in PuertoRicordquo Forest Ecology andManagement vol 124 no 1 pp 45ndash771999
[15] J Goma-Tchimbakala and F Bernhard-Reversat ldquoComparisonof litter dynamics in three plantations of an indigenous timber-tree species (Terminalia superba) and a natural tropical forestin Mayombe Congordquo Forest Ecology andManagement vol 229no 1ndash3 pp 304ndash313 2006
[16] J Barlow T A Gardner L V Ferreira and C A PeresldquoLitter fall and decomposition in primary secondary andplantation forests in the Brazilian Amazonrdquo Forest Ecology andManagement vol 247 no 1ndash3 pp 91ndash97 2007
[17] K Descheemaeker B Muys J Nyssen et al ldquoLitter productionand organic matter accumulation in exclosures of the Tigrayhighlands Ethiopiardquo Forest Ecology and Management vol 233no 1 pp 21ndash35 2006
[18] J Sawyer Plantations in the Tropics Environmental ConcernsIUCN Gland Switzerland 1993
[19] A E Lugo ldquoThe apparent paradox of reestablishing speciesrichness on degraded lands with tree monoculturesrdquo ForestEcology and Management vol 99 no 1-2 pp 9ndash19 1997
[20] J F Dames M C Scholes and C J Straker ldquoLitter pro-duction and accumulation in Pinus patula plantations of theMpumalanga Province South Africardquo Plant and Soil vol 203no 2 pp 183ndash190 1998
[21] J F Dames M C Scholes and C J Straker ldquoNutrient cyclingin a Pinus patula plantation in theMpumalanga Province SouthAfricardquo Applied Soil Ecology vol 20 no 3 pp 211ndash226 2002
[22] S E Attignon D Weibel T Lachat B Sinsin P Nagel andR Peveling ldquoLeaf litter breakdown in natural and plantationforests of the Lama forest reserve in BeninrdquoApplied Soil Ecologyvol 27 no 2 pp 109ndash124 2004
[23] A N Singh A S Raghubanshi and J S Singh ldquoComparativeperformance and restoration potential of two Albizia speciesplanted onmine spoil in a dry tropical region Indiardquo EcologicalEngineering vol 22 no 2 pp 123ndash140 2004
[24] D L Moorhead and R L Sinsabaugh ldquoA theoretical model oflitter decay and microbial interactionrdquo Ecological Monographsvol 76 no 2 pp 151ndash174 2006
[25] J M Duivenvoorden and J F Lips A Land-Ecological Study ofSoils Vegetation and Plant Diversity in Colombian AmazoniaTropenbos Series 12The Tropenbos Foundation WageningenThe Netherlands 1995
[26] H Marschner Mineral Nutrition of Higher Plants AcademicPress London UK 1995
[27] R Aerts ldquoClimate leaf litter chemistry and leaf litter decompo-sition in terrestrial ecosystems a triangular relationshiprdquoOikosvol 79 no 3 pp 439ndash449 1997
[28] F J Stevenson Cycles of Soil JohnWiley amp Sons New York NYUSA 1986
[29] D Lamb andDGilmour Issues in Forest Conservation Rehabili-tation and Restoration of Degraded Forests International Unionfor Conservation of Nature and Natural Resources and WorldWide Fund Cambridge UK 2003
Table 1 Mean values of structural parameters of the successionalpatches of mosquero (SPM) and forest plantations of neem (FPN)studied inAntioquia (Colombia) standard deviation in parentheses
mean square diameter119867 height119866 stand basal area
2 Material and Methods
21 Research Study Area This study was conducted in SantaFe de Antioquia northeastern Colombia (6∘541015840N 75∘811015840W560m of altitude)The annual average temperature sunlightprecipitation and evaporation of the region are 266∘C2172 h 1034mm and 1637mm respectively characterized bya pronounced annual water deficit derived from the Precip-itationEvaporation ratio of 063 The landscape consists ofhills with a low to medium slope formed from sedimentsfrom the TertiaryThe soils are alkaline and classified as TypicUstorthents (USDA soil taxonomy) the most dominant soiluse is grassland and unfortunately it is degraded by over-grazing The neem plantations studied here (active strategy)were established in 2004 on hillsides severely eroded byovergrazing since then forestry management practices havenot been carried out In the middle of these plantations havegrown natural successional patches (passive strategy) whichare constituted by native plant species heavily dominated bymosquero
22 Field and Laboratory Research Methods To evaluate thebiogeochemical cycle processes we established 20 circularplots of 250-m2 in forest plantations (FPN) and 13 similarplots in successional patches (SPM) (Table 1) In each plotthree circular litter traps (fine netting of 05-m2) were placed1-m above the soil surface Every 15 days for 1 year wecollected the litter material in each plot it means 60 samplesin FPN and 39 samples in SPM per sampling time
The litterfall was separated in the following fractions (a)neem leaves (NL) (b) mosquero leaves (ML) (c) leaves fromother species (OL) (d) wood material (WM) from branchesof lt2-cm diameter and small bark pieces (e) reproductivematerial (RM) and (f) other materials (OM) The dividedmaterial was oven dried at 65∘C and weighedThe samples ofNL andMLwere then separately combined and homogenizedfor every two 15-day periods (1 month) and a subsample wastaken for chemical analysis At the end of the year samplesfrom the accumulated litterfall layer or standing litter layeron the soil of the plantations and successional patches (a50 times 50 cm sample per plot) were collected Each samplewas separated in the same fractions than fine litterfall Eachfraction was dried at 65∘C until reaching constantmass (72 h)and weighed A composite and homogenized sample fromeach fraction was prepared for chemical analysis
The decomposition of neem and mosquero leaf litter wasstudied by installing 18 litter-bags (20 times 20 cm 2mm pores)with 3 g of senescent dry leaves per plant species Threelitter-bagswere randomly retrievedmonthlyThe residual leafmaterial was air-dried cleaned with a brush to remove soilparticles dried at 65∘C and weighed and named ldquoresidualdry matterrdquo (RDM) The samples from the three collectedlitter-bags in plantations and successional patches were thenseparately combined and homogenized for chemical analysisAdditionally in each plot of successional patches and forestplantations surface soil samples (0ndash10 cm depth) were col-lected Soil samples were also collected from 13 control siteswhere therewas not vegetation soil samples were transportedto laboratory for physical and chemical analyses
23 Physical and Chemical Analyses Leaf nutrient contentswere analyzed by different methods carbon (C) by theWalkley and Black method nitrogen (N) by the Kjeldahlmethod phosphorus (P) by the molybdate-blue methodcalcium (Ca)magnesium (Mg) and potassium (K) by atomicabsorption spectroscopy
In soil samples the methods used were pH (1 2 water)total N (Nt) (Kjeldahl method) available P (Bray-Kurtzrsquosmethod) exchangeable Ca Mg and K (1M ammoniumacetate atomic absorption spectroscopy) We also deter-mined soil bulk density (BD) and aggregate stability (AS)(Yoder method) Details about soil and plant analysis meth-ods are available in Westerman [8]
24 Statistical Analysis andCalculations Therate of potentialnutrient return (PNR) by the leaf litterfall was calculatedas the product of the nutrient concentration and the drymass of the leaf litterfall The retention of nutrients in thestanding litter (RNSL) was obtained by multiplying the dryweight of the leaves present in the standing litter and theirrespective concentrationWe calculated nutrient release fromthe decomposition coefficient 119896
119895
as proposed by Jenny etal [9] [119896
119895
= PNR(PNR + RNS)] The mean residencetime (MRT) of litterfall and nutrients was calculated as theinverse of 119896
119895
The real rate of nutrient return (RNR) from theleaf litterfall was calculated as the product of PNR and thecorresponding 119896
119895
coefficient [10]The weight loss in the litter-bags was expressed by a
simple exponential model [11]
119883119905
1198830
= 119890minus119896119905
(1)
where 119883119905
is the weight of the remaining material at moment119905 1198830
is the weight of the initial dry material 119890 is the basisof natural logarithm and 119896 is the decomposition rate Thetime required to obtain losses of 50 and 99 of the drymaterial was calculated as 119905
50
= minus0693119896 and 11990599
= minus4605119896respectively
Regression models were fitted using nonlinear regressionfor the weight loss of leaf material deposited in the litter-bagsLinear coefficient of determination (1198772) the Durbin-Watson(D-W) coefficient and the sum of the squares of the errorwere employed to select the models Correlation analyses
ISRN Soil Science 3
Table 2 Mean values of fractions for fine litter production (FLP) (kg haminus1 yrminus1) and standing litter (SL) (kg haminus1) in successional patches (SP)and forest plantations (FP) Standard deviation is in parentheses ML and NL leaf litter of mosquero and neem in their respective ecosystemOL other leaves RM reproductive material WM woody material OR other rests unidentified
FractionFLP SL
(kg haminus1 per two weeks) (kg haminus1 yrminus1) (kg haminus1 yrminus1)SPM FPN 119905 value SPM FPN SPM FPN 119905 value
decomposition time for half of the leaf litter 119905099
decomposition time for 99of the leaf litter 119896 yearly decomposition rate1198772 coefficient of determinationSSR sum of squared error D-W Durbin-Watson statistics
(r-Pearson 119875 le 005) were also used to determine associ-ations between weight loss rates and precipitation Becauselitter data were normally distributed a 119905-test was used todetermine the differences in fine litter production standinglitter and potential nutrient return between SPM and FPNTo compare soil parameters between control sites and bothrestoration strategies the Mann-Whitney (Wilcoxon) com-parison test (119875 le 005) was employed since these data werenot normally distributed The analyses were performed withStatgraphics Centurion XV (StatPoint Technologies Inc)
3 Results and Discussion
31 Fine Litter Production Accumulation and DecompositionThe results of this study clearly showed that there were sig-nificant differences between the active and passive strategiescharacterized here to activate soil biogeochemical nutrientcycles in tropical dry lands The annual production of leaflitter and total fine litter per unit area was 26-times and16-times higher in SPM than in FPN (Table 2) The higherfine litter production found in SPM represents a greaterpotential return of organic matter to these degraded soilsthan that of FPN The clear dominance of the leaf fractionin fine litter found in both types of ecosystems has beenreported in other studies [12]This also determines a potentialsource of nutrients for soil recovery because the higherdecomposition rate of this fraction represents a faster nutrientreturn path [13] By comparing the fine litterfall values withother studies the FPN were lower than those of tropicallowland forest plantations with ca of 5ndash10Mg haminus1 yminus1 [14ndash16]The fine litterfall values found in the SPM coincided withother tropical dry successional forests (03 to 42Mg haminus1 yminus1)as reported by Descheemaeker et al [17]
0
02
04
06
08
1
0 50 100 150 200 250
RDM
(ggminus
1
)
Time (days)
NeemMosquero
Figure 1 Residual dry matter (RDM) from leaf litter of neem (Aindica) and mosquero (C leptostachyus) Each point represents theaverage of three litter-bagsThe bars indicate the standard deviation
In the results we saw a contradiction about which typeof leaf litter decays faster The constant of decomposition(119896) showed that mosquero leaves are decomposed fasterthan neem leaves In fact it was noteworthy that the 119896constant of mosquero (34) was more than twice that ofneem (16) and the models predicted that the estimatedtime for 99 decomposition of leaf litter is 14 yr and 29 yrrespectively (Table 3) Furthermore at the end of the litter-bags experiment the RDM was 9 and 26 for mosqueroand neem respectively (Figure 1) However if we considerthe changes in the participation of neem andmosquero leavescollected in the litterfall traps (32 and 53 resp) with respect
4 ISRN Soil Science
Table 4 Meanmonthly values (plusmnSD) for leaf litter nutrient concentration (LLC ) and potential nutrient return (PNR kg haminus1) via leaf litterin successional patches of mosquero (SPM) and forest plantations of neem (FPN) studied Coefficient of variation () in parentheses
Nutrienta LLC () PNR (kg haminus1)119905 value 119890-value
119899SPM FPN SPM FPN
N 108 plusmn 013(119)
129 plusmn 031(242)
044 plusmn 035(789)
020 plusmn 018(1144) 2105 0047lowast 12
P 005 plusmn 001(156)
003 plusmn 001(190)
002 plusmn 002(792)
0005 plusmn 0004(867) 3052 0006lowastlowast 12
Ca 175 plusmn 033(189)
216 plusmn 065(301)
076 plusmn 060(797)
039 plusmn 044(820) 1721 0099NS 12
Mg 059 plusmn 008(139)
046 plusmn 006(139)
025 plusmn 021(834)
007 plusmn 006(645) 2829 0010lowastlowast 12
K 028 plusmn 013(449)
029 plusmn 014(493)
009 plusmn 008(802)
004 plusmn 003(890) 2226 0036lowast 12
aAnalytical methods in Westerman [8] lowast lowastlowastDenote significant differences between means of PNR at P values le 005 and le 001 respectively (119905-test)
to their participation in the standing litter (SL) (16 and 64Table 2) this suggests that neem leaves decomposed faster Itis necessary to consider that the neem leaves are fragile andcan be easily fragmented and for this reason they can be partof the OR fraction (plant remains unidentified) Thus theOR fraction (ORtotal) was only 2 in the fine litter (FLP)collected in the traps while this was 19 in the standinglitter (SL) Consequently we accepted that the k is a betterindicator and mosquero leaves decay faster In the litter-bagsexperiment the RDM of mosquero was only 9 which islower than that of neem 26 Also in the field the SL of FPNis higher suggesting that the decomposition of neem leavesis slower and for that reason they tend to accumulate on thesoil surface It has been reported that forest plantations withexotic species usually generate significant accumulations oflitter on the ground [18ndash20] Despite this accumulation thevalues found in the SL are relatively low in comparison tothose reported by other authors [10 20 21] Perhaps thisis a result of the young age of these forest plantations lackof canopy closure and low fine litterfall The 119896 values ofmosquero litter are comparable to those reported in tropicalarid ecosystems by several authors [15 22 23]
The high rate of decomposition of organic debris in SPMand therefore their low residence time are aspects of specialsignificance to the reactivation of biogeochemical nutrientcycle in these degraded soils [24] The inverse relationshipbetween the RDM in the litter-bags and the precipitation inSPM (r-Pearson = minus059 119875 lt 005) indicates the favorableeffect of the precipitation as a source of moisture for thedecomposer microorganisms perhaps this was not observedin the FPN because of the limitations of degrader microbes todecompose nonnative leaf material
32 Return Accumulation and Release of Nutrients In bothSPM and FPN nutrient concentrations in the leaf litter (LLC)followed the sequence Ca gt N gt Mg gt K gt P (Table 4)with the highest temporal variability for K The highconcentrations of Ca and Mg in the leaf litter found in thisstudy (175 and 216) differ from those found in other
tropical dry lowland forests [23] likely due to the high soilavailability of both nutrients (Table 6) By contrast the lowconcentration of K in the leaf litter (028ndash029) is near thelowest end of the pantropical interval (027 plusmn 011) [25]despite the availability of this nutrient in the soil Likely thelow soil CaMg ratio lt1 caused an abnormally high Mg plantuptake and altered the K uptake [26] In both ecosystemsthe most restrictive nutrient was P likely as a result of itsextreme scarcity in the soil (Table 6) which was reflected inthe high values of the leaf litter NP ratio (FPN 43 SPM 20)[10] These values of the NP ratio are much higher than thecritical value of 119 suggested by [27]
The potential nutrient return (PNR) through leaf litterfollowed the same sequence of concentrations (Table 4) andwas significantly higher in SPM because of the higher leaflitter production than in the FPN Furthermore the retentionof nutrients in the standing litter (RNSL) was higher inSPM which represents an important source of energy forthe micro- and mesofauna whose participation is a keyfunctional aspect to reactivate the biogeochemical cycling inthese degraded soils [28]
The real nutrient return (RNR) via leaf litter was higher inSPM for all nutrients (Table 5) This situation was primarilydetermined by the higher production of this fraction (ML)despite the fact that in FPN the 119870
119895
for some elements (C Pand K) was higher or similar (N) to those obtained in SPMThe low RNR of P also reflected the restrictive nature of thisnutrient for the productivity of both ecosystems [10]
In terms of the return and incorporation of organicmatter and C into the soil by leaf decomposition in theSL the superiority of SPM was notorious (Table 5) Thusthe real return of C (ML) in SPM was more than twicehigher than in the FPN (NL) In fact the highest rate of leaflitter decomposition of mosquero (higher values 119870
119895
and 119896)coincided with the highest contents of soil organic matter inSPM (Table 6)The times needed to achieve a decompositiondegree of 99 of leaves (14 yr for mosquero and 29 yr forneem) were close to those obtained from the inverse 119870
119895
inthe leaves of the SL (15 and 20 years resp)
ISRN Soil Science 5
Table 5 Indexes calculated for return retention and release of nutrients via leaf litter in successional patches of mosquero (SPM) and forestplantations of neem (FPN) (kg haminus1 yrminus1)
Table 6 Mean values (plusmnSD) for some soil parameters (0ndash10 cm) in successional patches of mosquero (SPM) forest plantations of neem(FPN) and control sites without vegetation studied in Santafe de Antioquia (Colombia)
AE () 728 plusmn 106 685 plusmn 129 094 801 plusmn 95 110aAnalytical methods available in Westerman [8]PCI parameter change index (FPNcontrol or SPMcontrol) SOM soil organic matter ECEC effective cation exchange capacity BD bulk density ASaggregate stability lowastIndicates significant difference with control sites (Mann-Whitney P le 005)
N and P were released more slowly (lower values of119896119895
) than other nutrients and they are expected to remainlonger in the above ground leaf litter as indicated by MRTvalues (Table 5) P was released faster in FPN (119870
119895
= 068MRT = 147 years) while N was released at similar rates inboth ecosystems (119870
119895
= 057 MRT = 176 years) In bothecosystems Ca had the highest release The time necessaryfor the effective release of all elements considered in bothecosystems was 11ndash181 years
33 Soil Reclamation Soils of both SPM and FPN showedchanges of some properties with respect to soil of control sites(without vegetation) (Table 6) In SPM significant increaseswere detected with respect to the control sites on parameterssuch as soil organic matter the content (SOM) exchange-able Mg and Ca and effective cation exchange capacity(ECEC)On the other hand in FPNwere observed significantincreases in SOM totalN (Nt) available-P and exchangeable-K and significant reduction in bulk density (BD)
Despite their short period of time for both strategiesthe contributions of fine litter and its decomposition haveimproved various soil properties of these degraded landsThesharp increases of SOM observed (compared to control sites)also increased soil moisture retention capacity and soil cationexchange key aspects in the reclamation of soils of degradeddry land Although FPN showed a significant increase of P
its very low concentration in the soil determined a severeconstraint on ecosystem primary productivity
4 Conclusions
From the perspective of land restoration both modelsshowed different advantages The passive model representedby the SPM showed a higher dynamics in the reactivation ofsoil biogeochemical cycles It is expected that as the succes-sional process continues the consequently greater complexityof the ecosystem will lead to an effective improvement notonly on the soil but also on ecosystem functions On theother hand the active model represented by the FPN showedsignificant improvements in soil parameters even thoughthe returns of litter and nutrients were lower Likely thissituation is the result of differences in litter contributionswhose potential effect on soil rehabilitation has not beenfully evaluated These are issues to consider in selecting arestoration model and the degree and speed expected ofthe degradation process Thus an active model should beconsideredwhen the rate of degradation of the area of interestis high because the planted species can be established quicklyand create better conditions for a more diverse biologicalcommunity as pointed by [5] When the state and rate ofdegradation are not severe themost appropriatemodelmightbe the passive restoration allowing the ecosystem a natural
6 ISRN Soil Science
recover [29] which had advantages from ecological andeconomic perspectives
Acknowledgments
The authors thank the Direction of Research of the Universi-dadNacional de Colombia for financial support of the ProjectldquoRestoration of lands in a process of desertificationwith neemplantations (Azadirachta indica) in Western Antioquiardquo JuanD Leon was supported by Convocatoria Nacional de Investi-gacion y de Creacion Artıstica de la Universidad Nacional deColombia 2010ndash2012 They also thank the BiogeochemistryLaboratory of the Universidad Nacional de Colombia atMedellin campus The authors are grateful to A N Marın LF Osorio J C Guingue G E Mazo and N Alvarez for theirtechnical collaboration
References
[1] Y Zha and J Gao ldquoCharacteristics of desertification and itsrehabilitation in Chinardquo Journal of Arid Environments vol 37no 3 pp 419ndash432 1997
[2] J F Reynolds and D M Stafford Smith Global DesertificationDo Humans Cause Deserts Vol 88 University Press BerlinGermany 2002
[3] Plan de Accion Nacional de Lucha Contra la Desertificacion y laSequıa en Colombia (PAN) Ministerio de Ambiente Vivienday Desarrollo Territorial Bogota Colombia 2004
[4] D Celentano R A Zahawi B Finegan R Ostertag R J Coleand K D Holl ldquoLitterfall dynamics under different tropicalforest restoration strategies in Costa Ricardquo Biotropica vol 43no 3 pp 279ndash287 2011
[5] S D Reay and D A Norton ldquoAssessing the success of restora-tion plantings in a temperate New Zealand forestrdquo RestorationEcology vol 7 no 3 pp 298ndash308 1999
[6] K D Holl ldquoTropical moist forest restorationrdquo in Handbook ofEcological Restoration M R Perrow and A J Davy Eds pp539ndash558 Cambridge University Press Cambridge UK 2002
[7] J Schrautzer A Rinker K Jensen F Muller P Schwartzeand C Dier Ben ldquoSuccession and restoration of drained fensperspectives from northwestern Europerdquo in Linking Restorationand Ecological Succession L R Walker J Walker and R JHobbs Eds pp 90ndash120 Springer New York NY USA 2007
[8] R L Westerman Soil Testing and Plant Analysis Soil ScienceSociety of America Madison Wis USA 1990
[9] H Jenny S Gessel and F Bingham ldquoComparative study ofdecomposition of organic matter in temperate and tropicalregionsrdquo Soil Science vol 68 pp 419ndash432 1949
[10] J D Leon M I Gonzalez and J F Gallardo ldquoCiclos bio-geoquımicos en bosques naturales y plantaciones de conıferasen ecosistemas de alta montana de Colombiardquo Revista BiologıaTropical vol 59 pp 1883ndash1894 2011
[11] J Olson ldquoEnergy storage and balance of producers and decom-poser in ecological systemsrdquo Ecology vol 44 pp 322ndash331 1963
[12] V Meentemeyer E O Box and R Thompson ldquoWorld patternsand amounts of terrestrial plant litter productionrdquo Biosciencevol 32 pp 125ndash128 1982
[13] C Strojan F Turner and R Castetter ldquoLitter fall from shrubs inthe northernMojave desertrdquo Ecology vol 60 pp 891ndash900 1979
[14] J A Parrotta ldquoProductivity nutrient cycling and succession insingle- and mixed-species plantations of Casuarina equisetifo-lia Eucalyptus robusta and Leucaena leucocephala in PuertoRicordquo Forest Ecology andManagement vol 124 no 1 pp 45ndash771999
[15] J Goma-Tchimbakala and F Bernhard-Reversat ldquoComparisonof litter dynamics in three plantations of an indigenous timber-tree species (Terminalia superba) and a natural tropical forestin Mayombe Congordquo Forest Ecology andManagement vol 229no 1ndash3 pp 304ndash313 2006
[16] J Barlow T A Gardner L V Ferreira and C A PeresldquoLitter fall and decomposition in primary secondary andplantation forests in the Brazilian Amazonrdquo Forest Ecology andManagement vol 247 no 1ndash3 pp 91ndash97 2007
[17] K Descheemaeker B Muys J Nyssen et al ldquoLitter productionand organic matter accumulation in exclosures of the Tigrayhighlands Ethiopiardquo Forest Ecology and Management vol 233no 1 pp 21ndash35 2006
[18] J Sawyer Plantations in the Tropics Environmental ConcernsIUCN Gland Switzerland 1993
[19] A E Lugo ldquoThe apparent paradox of reestablishing speciesrichness on degraded lands with tree monoculturesrdquo ForestEcology and Management vol 99 no 1-2 pp 9ndash19 1997
[20] J F Dames M C Scholes and C J Straker ldquoLitter pro-duction and accumulation in Pinus patula plantations of theMpumalanga Province South Africardquo Plant and Soil vol 203no 2 pp 183ndash190 1998
[21] J F Dames M C Scholes and C J Straker ldquoNutrient cyclingin a Pinus patula plantation in theMpumalanga Province SouthAfricardquo Applied Soil Ecology vol 20 no 3 pp 211ndash226 2002
[22] S E Attignon D Weibel T Lachat B Sinsin P Nagel andR Peveling ldquoLeaf litter breakdown in natural and plantationforests of the Lama forest reserve in BeninrdquoApplied Soil Ecologyvol 27 no 2 pp 109ndash124 2004
[23] A N Singh A S Raghubanshi and J S Singh ldquoComparativeperformance and restoration potential of two Albizia speciesplanted onmine spoil in a dry tropical region Indiardquo EcologicalEngineering vol 22 no 2 pp 123ndash140 2004
[24] D L Moorhead and R L Sinsabaugh ldquoA theoretical model oflitter decay and microbial interactionrdquo Ecological Monographsvol 76 no 2 pp 151ndash174 2006
[25] J M Duivenvoorden and J F Lips A Land-Ecological Study ofSoils Vegetation and Plant Diversity in Colombian AmazoniaTropenbos Series 12The Tropenbos Foundation WageningenThe Netherlands 1995
[26] H Marschner Mineral Nutrition of Higher Plants AcademicPress London UK 1995
[27] R Aerts ldquoClimate leaf litter chemistry and leaf litter decompo-sition in terrestrial ecosystems a triangular relationshiprdquoOikosvol 79 no 3 pp 439ndash449 1997
[28] F J Stevenson Cycles of Soil JohnWiley amp Sons New York NYUSA 1986
[29] D Lamb andDGilmour Issues in Forest Conservation Rehabili-tation and Restoration of Degraded Forests International Unionfor Conservation of Nature and Natural Resources and WorldWide Fund Cambridge UK 2003
Table 2 Mean values of fractions for fine litter production (FLP) (kg haminus1 yrminus1) and standing litter (SL) (kg haminus1) in successional patches (SP)and forest plantations (FP) Standard deviation is in parentheses ML and NL leaf litter of mosquero and neem in their respective ecosystemOL other leaves RM reproductive material WM woody material OR other rests unidentified
FractionFLP SL
(kg haminus1 per two weeks) (kg haminus1 yrminus1) (kg haminus1 yrminus1)SPM FPN 119905 value SPM FPN SPM FPN 119905 value
decomposition time for half of the leaf litter 119905099
decomposition time for 99of the leaf litter 119896 yearly decomposition rate1198772 coefficient of determinationSSR sum of squared error D-W Durbin-Watson statistics
(r-Pearson 119875 le 005) were also used to determine associ-ations between weight loss rates and precipitation Becauselitter data were normally distributed a 119905-test was used todetermine the differences in fine litter production standinglitter and potential nutrient return between SPM and FPNTo compare soil parameters between control sites and bothrestoration strategies the Mann-Whitney (Wilcoxon) com-parison test (119875 le 005) was employed since these data werenot normally distributed The analyses were performed withStatgraphics Centurion XV (StatPoint Technologies Inc)
3 Results and Discussion
31 Fine Litter Production Accumulation and DecompositionThe results of this study clearly showed that there were sig-nificant differences between the active and passive strategiescharacterized here to activate soil biogeochemical nutrientcycles in tropical dry lands The annual production of leaflitter and total fine litter per unit area was 26-times and16-times higher in SPM than in FPN (Table 2) The higherfine litter production found in SPM represents a greaterpotential return of organic matter to these degraded soilsthan that of FPN The clear dominance of the leaf fractionin fine litter found in both types of ecosystems has beenreported in other studies [12]This also determines a potentialsource of nutrients for soil recovery because the higherdecomposition rate of this fraction represents a faster nutrientreturn path [13] By comparing the fine litterfall values withother studies the FPN were lower than those of tropicallowland forest plantations with ca of 5ndash10Mg haminus1 yminus1 [14ndash16]The fine litterfall values found in the SPM coincided withother tropical dry successional forests (03 to 42Mg haminus1 yminus1)as reported by Descheemaeker et al [17]
0
02
04
06
08
1
0 50 100 150 200 250
RDM
(ggminus
1
)
Time (days)
NeemMosquero
Figure 1 Residual dry matter (RDM) from leaf litter of neem (Aindica) and mosquero (C leptostachyus) Each point represents theaverage of three litter-bagsThe bars indicate the standard deviation
In the results we saw a contradiction about which typeof leaf litter decays faster The constant of decomposition(119896) showed that mosquero leaves are decomposed fasterthan neem leaves In fact it was noteworthy that the 119896constant of mosquero (34) was more than twice that ofneem (16) and the models predicted that the estimatedtime for 99 decomposition of leaf litter is 14 yr and 29 yrrespectively (Table 3) Furthermore at the end of the litter-bags experiment the RDM was 9 and 26 for mosqueroand neem respectively (Figure 1) However if we considerthe changes in the participation of neem andmosquero leavescollected in the litterfall traps (32 and 53 resp) with respect
4 ISRN Soil Science
Table 4 Meanmonthly values (plusmnSD) for leaf litter nutrient concentration (LLC ) and potential nutrient return (PNR kg haminus1) via leaf litterin successional patches of mosquero (SPM) and forest plantations of neem (FPN) studied Coefficient of variation () in parentheses
Nutrienta LLC () PNR (kg haminus1)119905 value 119890-value
119899SPM FPN SPM FPN
N 108 plusmn 013(119)
129 plusmn 031(242)
044 plusmn 035(789)
020 plusmn 018(1144) 2105 0047lowast 12
P 005 plusmn 001(156)
003 plusmn 001(190)
002 plusmn 002(792)
0005 plusmn 0004(867) 3052 0006lowastlowast 12
Ca 175 plusmn 033(189)
216 plusmn 065(301)
076 plusmn 060(797)
039 plusmn 044(820) 1721 0099NS 12
Mg 059 plusmn 008(139)
046 plusmn 006(139)
025 plusmn 021(834)
007 plusmn 006(645) 2829 0010lowastlowast 12
K 028 plusmn 013(449)
029 plusmn 014(493)
009 plusmn 008(802)
004 plusmn 003(890) 2226 0036lowast 12
aAnalytical methods in Westerman [8] lowast lowastlowastDenote significant differences between means of PNR at P values le 005 and le 001 respectively (119905-test)
to their participation in the standing litter (SL) (16 and 64Table 2) this suggests that neem leaves decomposed faster Itis necessary to consider that the neem leaves are fragile andcan be easily fragmented and for this reason they can be partof the OR fraction (plant remains unidentified) Thus theOR fraction (ORtotal) was only 2 in the fine litter (FLP)collected in the traps while this was 19 in the standinglitter (SL) Consequently we accepted that the k is a betterindicator and mosquero leaves decay faster In the litter-bagsexperiment the RDM of mosquero was only 9 which islower than that of neem 26 Also in the field the SL of FPNis higher suggesting that the decomposition of neem leavesis slower and for that reason they tend to accumulate on thesoil surface It has been reported that forest plantations withexotic species usually generate significant accumulations oflitter on the ground [18ndash20] Despite this accumulation thevalues found in the SL are relatively low in comparison tothose reported by other authors [10 20 21] Perhaps thisis a result of the young age of these forest plantations lackof canopy closure and low fine litterfall The 119896 values ofmosquero litter are comparable to those reported in tropicalarid ecosystems by several authors [15 22 23]
The high rate of decomposition of organic debris in SPMand therefore their low residence time are aspects of specialsignificance to the reactivation of biogeochemical nutrientcycle in these degraded soils [24] The inverse relationshipbetween the RDM in the litter-bags and the precipitation inSPM (r-Pearson = minus059 119875 lt 005) indicates the favorableeffect of the precipitation as a source of moisture for thedecomposer microorganisms perhaps this was not observedin the FPN because of the limitations of degrader microbes todecompose nonnative leaf material
32 Return Accumulation and Release of Nutrients In bothSPM and FPN nutrient concentrations in the leaf litter (LLC)followed the sequence Ca gt N gt Mg gt K gt P (Table 4)with the highest temporal variability for K The highconcentrations of Ca and Mg in the leaf litter found in thisstudy (175 and 216) differ from those found in other
tropical dry lowland forests [23] likely due to the high soilavailability of both nutrients (Table 6) By contrast the lowconcentration of K in the leaf litter (028ndash029) is near thelowest end of the pantropical interval (027 plusmn 011) [25]despite the availability of this nutrient in the soil Likely thelow soil CaMg ratio lt1 caused an abnormally high Mg plantuptake and altered the K uptake [26] In both ecosystemsthe most restrictive nutrient was P likely as a result of itsextreme scarcity in the soil (Table 6) which was reflected inthe high values of the leaf litter NP ratio (FPN 43 SPM 20)[10] These values of the NP ratio are much higher than thecritical value of 119 suggested by [27]
The potential nutrient return (PNR) through leaf litterfollowed the same sequence of concentrations (Table 4) andwas significantly higher in SPM because of the higher leaflitter production than in the FPN Furthermore the retentionof nutrients in the standing litter (RNSL) was higher inSPM which represents an important source of energy forthe micro- and mesofauna whose participation is a keyfunctional aspect to reactivate the biogeochemical cycling inthese degraded soils [28]
The real nutrient return (RNR) via leaf litter was higher inSPM for all nutrients (Table 5) This situation was primarilydetermined by the higher production of this fraction (ML)despite the fact that in FPN the 119870
119895
for some elements (C Pand K) was higher or similar (N) to those obtained in SPMThe low RNR of P also reflected the restrictive nature of thisnutrient for the productivity of both ecosystems [10]
In terms of the return and incorporation of organicmatter and C into the soil by leaf decomposition in theSL the superiority of SPM was notorious (Table 5) Thusthe real return of C (ML) in SPM was more than twicehigher than in the FPN (NL) In fact the highest rate of leaflitter decomposition of mosquero (higher values 119870
119895
and 119896)coincided with the highest contents of soil organic matter inSPM (Table 6)The times needed to achieve a decompositiondegree of 99 of leaves (14 yr for mosquero and 29 yr forneem) were close to those obtained from the inverse 119870
119895
inthe leaves of the SL (15 and 20 years resp)
ISRN Soil Science 5
Table 5 Indexes calculated for return retention and release of nutrients via leaf litter in successional patches of mosquero (SPM) and forestplantations of neem (FPN) (kg haminus1 yrminus1)
Table 6 Mean values (plusmnSD) for some soil parameters (0ndash10 cm) in successional patches of mosquero (SPM) forest plantations of neem(FPN) and control sites without vegetation studied in Santafe de Antioquia (Colombia)
AE () 728 plusmn 106 685 plusmn 129 094 801 plusmn 95 110aAnalytical methods available in Westerman [8]PCI parameter change index (FPNcontrol or SPMcontrol) SOM soil organic matter ECEC effective cation exchange capacity BD bulk density ASaggregate stability lowastIndicates significant difference with control sites (Mann-Whitney P le 005)
N and P were released more slowly (lower values of119896119895
) than other nutrients and they are expected to remainlonger in the above ground leaf litter as indicated by MRTvalues (Table 5) P was released faster in FPN (119870
119895
= 068MRT = 147 years) while N was released at similar rates inboth ecosystems (119870
119895
= 057 MRT = 176 years) In bothecosystems Ca had the highest release The time necessaryfor the effective release of all elements considered in bothecosystems was 11ndash181 years
33 Soil Reclamation Soils of both SPM and FPN showedchanges of some properties with respect to soil of control sites(without vegetation) (Table 6) In SPM significant increaseswere detected with respect to the control sites on parameterssuch as soil organic matter the content (SOM) exchange-able Mg and Ca and effective cation exchange capacity(ECEC)On the other hand in FPNwere observed significantincreases in SOM totalN (Nt) available-P and exchangeable-K and significant reduction in bulk density (BD)
Despite their short period of time for both strategiesthe contributions of fine litter and its decomposition haveimproved various soil properties of these degraded landsThesharp increases of SOM observed (compared to control sites)also increased soil moisture retention capacity and soil cationexchange key aspects in the reclamation of soils of degradeddry land Although FPN showed a significant increase of P
its very low concentration in the soil determined a severeconstraint on ecosystem primary productivity
4 Conclusions
From the perspective of land restoration both modelsshowed different advantages The passive model representedby the SPM showed a higher dynamics in the reactivation ofsoil biogeochemical cycles It is expected that as the succes-sional process continues the consequently greater complexityof the ecosystem will lead to an effective improvement notonly on the soil but also on ecosystem functions On theother hand the active model represented by the FPN showedsignificant improvements in soil parameters even thoughthe returns of litter and nutrients were lower Likely thissituation is the result of differences in litter contributionswhose potential effect on soil rehabilitation has not beenfully evaluated These are issues to consider in selecting arestoration model and the degree and speed expected ofthe degradation process Thus an active model should beconsideredwhen the rate of degradation of the area of interestis high because the planted species can be established quicklyand create better conditions for a more diverse biologicalcommunity as pointed by [5] When the state and rate ofdegradation are not severe themost appropriatemodelmightbe the passive restoration allowing the ecosystem a natural
6 ISRN Soil Science
recover [29] which had advantages from ecological andeconomic perspectives
Acknowledgments
The authors thank the Direction of Research of the Universi-dadNacional de Colombia for financial support of the ProjectldquoRestoration of lands in a process of desertificationwith neemplantations (Azadirachta indica) in Western Antioquiardquo JuanD Leon was supported by Convocatoria Nacional de Investi-gacion y de Creacion Artıstica de la Universidad Nacional deColombia 2010ndash2012 They also thank the BiogeochemistryLaboratory of the Universidad Nacional de Colombia atMedellin campus The authors are grateful to A N Marın LF Osorio J C Guingue G E Mazo and N Alvarez for theirtechnical collaboration
References
[1] Y Zha and J Gao ldquoCharacteristics of desertification and itsrehabilitation in Chinardquo Journal of Arid Environments vol 37no 3 pp 419ndash432 1997
[2] J F Reynolds and D M Stafford Smith Global DesertificationDo Humans Cause Deserts Vol 88 University Press BerlinGermany 2002
[3] Plan de Accion Nacional de Lucha Contra la Desertificacion y laSequıa en Colombia (PAN) Ministerio de Ambiente Vivienday Desarrollo Territorial Bogota Colombia 2004
[4] D Celentano R A Zahawi B Finegan R Ostertag R J Coleand K D Holl ldquoLitterfall dynamics under different tropicalforest restoration strategies in Costa Ricardquo Biotropica vol 43no 3 pp 279ndash287 2011
[5] S D Reay and D A Norton ldquoAssessing the success of restora-tion plantings in a temperate New Zealand forestrdquo RestorationEcology vol 7 no 3 pp 298ndash308 1999
[6] K D Holl ldquoTropical moist forest restorationrdquo in Handbook ofEcological Restoration M R Perrow and A J Davy Eds pp539ndash558 Cambridge University Press Cambridge UK 2002
[7] J Schrautzer A Rinker K Jensen F Muller P Schwartzeand C Dier Ben ldquoSuccession and restoration of drained fensperspectives from northwestern Europerdquo in Linking Restorationand Ecological Succession L R Walker J Walker and R JHobbs Eds pp 90ndash120 Springer New York NY USA 2007
[8] R L Westerman Soil Testing and Plant Analysis Soil ScienceSociety of America Madison Wis USA 1990
[9] H Jenny S Gessel and F Bingham ldquoComparative study ofdecomposition of organic matter in temperate and tropicalregionsrdquo Soil Science vol 68 pp 419ndash432 1949
[10] J D Leon M I Gonzalez and J F Gallardo ldquoCiclos bio-geoquımicos en bosques naturales y plantaciones de conıferasen ecosistemas de alta montana de Colombiardquo Revista BiologıaTropical vol 59 pp 1883ndash1894 2011
[11] J Olson ldquoEnergy storage and balance of producers and decom-poser in ecological systemsrdquo Ecology vol 44 pp 322ndash331 1963
[12] V Meentemeyer E O Box and R Thompson ldquoWorld patternsand amounts of terrestrial plant litter productionrdquo Biosciencevol 32 pp 125ndash128 1982
[13] C Strojan F Turner and R Castetter ldquoLitter fall from shrubs inthe northernMojave desertrdquo Ecology vol 60 pp 891ndash900 1979
[14] J A Parrotta ldquoProductivity nutrient cycling and succession insingle- and mixed-species plantations of Casuarina equisetifo-lia Eucalyptus robusta and Leucaena leucocephala in PuertoRicordquo Forest Ecology andManagement vol 124 no 1 pp 45ndash771999
[15] J Goma-Tchimbakala and F Bernhard-Reversat ldquoComparisonof litter dynamics in three plantations of an indigenous timber-tree species (Terminalia superba) and a natural tropical forestin Mayombe Congordquo Forest Ecology andManagement vol 229no 1ndash3 pp 304ndash313 2006
[16] J Barlow T A Gardner L V Ferreira and C A PeresldquoLitter fall and decomposition in primary secondary andplantation forests in the Brazilian Amazonrdquo Forest Ecology andManagement vol 247 no 1ndash3 pp 91ndash97 2007
[17] K Descheemaeker B Muys J Nyssen et al ldquoLitter productionand organic matter accumulation in exclosures of the Tigrayhighlands Ethiopiardquo Forest Ecology and Management vol 233no 1 pp 21ndash35 2006
[18] J Sawyer Plantations in the Tropics Environmental ConcernsIUCN Gland Switzerland 1993
[19] A E Lugo ldquoThe apparent paradox of reestablishing speciesrichness on degraded lands with tree monoculturesrdquo ForestEcology and Management vol 99 no 1-2 pp 9ndash19 1997
[20] J F Dames M C Scholes and C J Straker ldquoLitter pro-duction and accumulation in Pinus patula plantations of theMpumalanga Province South Africardquo Plant and Soil vol 203no 2 pp 183ndash190 1998
[21] J F Dames M C Scholes and C J Straker ldquoNutrient cyclingin a Pinus patula plantation in theMpumalanga Province SouthAfricardquo Applied Soil Ecology vol 20 no 3 pp 211ndash226 2002
[22] S E Attignon D Weibel T Lachat B Sinsin P Nagel andR Peveling ldquoLeaf litter breakdown in natural and plantationforests of the Lama forest reserve in BeninrdquoApplied Soil Ecologyvol 27 no 2 pp 109ndash124 2004
[23] A N Singh A S Raghubanshi and J S Singh ldquoComparativeperformance and restoration potential of two Albizia speciesplanted onmine spoil in a dry tropical region Indiardquo EcologicalEngineering vol 22 no 2 pp 123ndash140 2004
[24] D L Moorhead and R L Sinsabaugh ldquoA theoretical model oflitter decay and microbial interactionrdquo Ecological Monographsvol 76 no 2 pp 151ndash174 2006
[25] J M Duivenvoorden and J F Lips A Land-Ecological Study ofSoils Vegetation and Plant Diversity in Colombian AmazoniaTropenbos Series 12The Tropenbos Foundation WageningenThe Netherlands 1995
[26] H Marschner Mineral Nutrition of Higher Plants AcademicPress London UK 1995
[27] R Aerts ldquoClimate leaf litter chemistry and leaf litter decompo-sition in terrestrial ecosystems a triangular relationshiprdquoOikosvol 79 no 3 pp 439ndash449 1997
[28] F J Stevenson Cycles of Soil JohnWiley amp Sons New York NYUSA 1986
[29] D Lamb andDGilmour Issues in Forest Conservation Rehabili-tation and Restoration of Degraded Forests International Unionfor Conservation of Nature and Natural Resources and WorldWide Fund Cambridge UK 2003
Table 4 Meanmonthly values (plusmnSD) for leaf litter nutrient concentration (LLC ) and potential nutrient return (PNR kg haminus1) via leaf litterin successional patches of mosquero (SPM) and forest plantations of neem (FPN) studied Coefficient of variation () in parentheses
Nutrienta LLC () PNR (kg haminus1)119905 value 119890-value
119899SPM FPN SPM FPN
N 108 plusmn 013(119)
129 plusmn 031(242)
044 plusmn 035(789)
020 plusmn 018(1144) 2105 0047lowast 12
P 005 plusmn 001(156)
003 plusmn 001(190)
002 plusmn 002(792)
0005 plusmn 0004(867) 3052 0006lowastlowast 12
Ca 175 plusmn 033(189)
216 plusmn 065(301)
076 plusmn 060(797)
039 plusmn 044(820) 1721 0099NS 12
Mg 059 plusmn 008(139)
046 plusmn 006(139)
025 plusmn 021(834)
007 plusmn 006(645) 2829 0010lowastlowast 12
K 028 plusmn 013(449)
029 plusmn 014(493)
009 plusmn 008(802)
004 plusmn 003(890) 2226 0036lowast 12
aAnalytical methods in Westerman [8] lowast lowastlowastDenote significant differences between means of PNR at P values le 005 and le 001 respectively (119905-test)
to their participation in the standing litter (SL) (16 and 64Table 2) this suggests that neem leaves decomposed faster Itis necessary to consider that the neem leaves are fragile andcan be easily fragmented and for this reason they can be partof the OR fraction (plant remains unidentified) Thus theOR fraction (ORtotal) was only 2 in the fine litter (FLP)collected in the traps while this was 19 in the standinglitter (SL) Consequently we accepted that the k is a betterindicator and mosquero leaves decay faster In the litter-bagsexperiment the RDM of mosquero was only 9 which islower than that of neem 26 Also in the field the SL of FPNis higher suggesting that the decomposition of neem leavesis slower and for that reason they tend to accumulate on thesoil surface It has been reported that forest plantations withexotic species usually generate significant accumulations oflitter on the ground [18ndash20] Despite this accumulation thevalues found in the SL are relatively low in comparison tothose reported by other authors [10 20 21] Perhaps thisis a result of the young age of these forest plantations lackof canopy closure and low fine litterfall The 119896 values ofmosquero litter are comparable to those reported in tropicalarid ecosystems by several authors [15 22 23]
The high rate of decomposition of organic debris in SPMand therefore their low residence time are aspects of specialsignificance to the reactivation of biogeochemical nutrientcycle in these degraded soils [24] The inverse relationshipbetween the RDM in the litter-bags and the precipitation inSPM (r-Pearson = minus059 119875 lt 005) indicates the favorableeffect of the precipitation as a source of moisture for thedecomposer microorganisms perhaps this was not observedin the FPN because of the limitations of degrader microbes todecompose nonnative leaf material
32 Return Accumulation and Release of Nutrients In bothSPM and FPN nutrient concentrations in the leaf litter (LLC)followed the sequence Ca gt N gt Mg gt K gt P (Table 4)with the highest temporal variability for K The highconcentrations of Ca and Mg in the leaf litter found in thisstudy (175 and 216) differ from those found in other
tropical dry lowland forests [23] likely due to the high soilavailability of both nutrients (Table 6) By contrast the lowconcentration of K in the leaf litter (028ndash029) is near thelowest end of the pantropical interval (027 plusmn 011) [25]despite the availability of this nutrient in the soil Likely thelow soil CaMg ratio lt1 caused an abnormally high Mg plantuptake and altered the K uptake [26] In both ecosystemsthe most restrictive nutrient was P likely as a result of itsextreme scarcity in the soil (Table 6) which was reflected inthe high values of the leaf litter NP ratio (FPN 43 SPM 20)[10] These values of the NP ratio are much higher than thecritical value of 119 suggested by [27]
The potential nutrient return (PNR) through leaf litterfollowed the same sequence of concentrations (Table 4) andwas significantly higher in SPM because of the higher leaflitter production than in the FPN Furthermore the retentionof nutrients in the standing litter (RNSL) was higher inSPM which represents an important source of energy forthe micro- and mesofauna whose participation is a keyfunctional aspect to reactivate the biogeochemical cycling inthese degraded soils [28]
The real nutrient return (RNR) via leaf litter was higher inSPM for all nutrients (Table 5) This situation was primarilydetermined by the higher production of this fraction (ML)despite the fact that in FPN the 119870
119895
for some elements (C Pand K) was higher or similar (N) to those obtained in SPMThe low RNR of P also reflected the restrictive nature of thisnutrient for the productivity of both ecosystems [10]
In terms of the return and incorporation of organicmatter and C into the soil by leaf decomposition in theSL the superiority of SPM was notorious (Table 5) Thusthe real return of C (ML) in SPM was more than twicehigher than in the FPN (NL) In fact the highest rate of leaflitter decomposition of mosquero (higher values 119870
119895
and 119896)coincided with the highest contents of soil organic matter inSPM (Table 6)The times needed to achieve a decompositiondegree of 99 of leaves (14 yr for mosquero and 29 yr forneem) were close to those obtained from the inverse 119870
119895
inthe leaves of the SL (15 and 20 years resp)
ISRN Soil Science 5
Table 5 Indexes calculated for return retention and release of nutrients via leaf litter in successional patches of mosquero (SPM) and forestplantations of neem (FPN) (kg haminus1 yrminus1)
Table 6 Mean values (plusmnSD) for some soil parameters (0ndash10 cm) in successional patches of mosquero (SPM) forest plantations of neem(FPN) and control sites without vegetation studied in Santafe de Antioquia (Colombia)
AE () 728 plusmn 106 685 plusmn 129 094 801 plusmn 95 110aAnalytical methods available in Westerman [8]PCI parameter change index (FPNcontrol or SPMcontrol) SOM soil organic matter ECEC effective cation exchange capacity BD bulk density ASaggregate stability lowastIndicates significant difference with control sites (Mann-Whitney P le 005)
N and P were released more slowly (lower values of119896119895
) than other nutrients and they are expected to remainlonger in the above ground leaf litter as indicated by MRTvalues (Table 5) P was released faster in FPN (119870
119895
= 068MRT = 147 years) while N was released at similar rates inboth ecosystems (119870
119895
= 057 MRT = 176 years) In bothecosystems Ca had the highest release The time necessaryfor the effective release of all elements considered in bothecosystems was 11ndash181 years
33 Soil Reclamation Soils of both SPM and FPN showedchanges of some properties with respect to soil of control sites(without vegetation) (Table 6) In SPM significant increaseswere detected with respect to the control sites on parameterssuch as soil organic matter the content (SOM) exchange-able Mg and Ca and effective cation exchange capacity(ECEC)On the other hand in FPNwere observed significantincreases in SOM totalN (Nt) available-P and exchangeable-K and significant reduction in bulk density (BD)
Despite their short period of time for both strategiesthe contributions of fine litter and its decomposition haveimproved various soil properties of these degraded landsThesharp increases of SOM observed (compared to control sites)also increased soil moisture retention capacity and soil cationexchange key aspects in the reclamation of soils of degradeddry land Although FPN showed a significant increase of P
its very low concentration in the soil determined a severeconstraint on ecosystem primary productivity
4 Conclusions
From the perspective of land restoration both modelsshowed different advantages The passive model representedby the SPM showed a higher dynamics in the reactivation ofsoil biogeochemical cycles It is expected that as the succes-sional process continues the consequently greater complexityof the ecosystem will lead to an effective improvement notonly on the soil but also on ecosystem functions On theother hand the active model represented by the FPN showedsignificant improvements in soil parameters even thoughthe returns of litter and nutrients were lower Likely thissituation is the result of differences in litter contributionswhose potential effect on soil rehabilitation has not beenfully evaluated These are issues to consider in selecting arestoration model and the degree and speed expected ofthe degradation process Thus an active model should beconsideredwhen the rate of degradation of the area of interestis high because the planted species can be established quicklyand create better conditions for a more diverse biologicalcommunity as pointed by [5] When the state and rate ofdegradation are not severe themost appropriatemodelmightbe the passive restoration allowing the ecosystem a natural
6 ISRN Soil Science
recover [29] which had advantages from ecological andeconomic perspectives
Acknowledgments
The authors thank the Direction of Research of the Universi-dadNacional de Colombia for financial support of the ProjectldquoRestoration of lands in a process of desertificationwith neemplantations (Azadirachta indica) in Western Antioquiardquo JuanD Leon was supported by Convocatoria Nacional de Investi-gacion y de Creacion Artıstica de la Universidad Nacional deColombia 2010ndash2012 They also thank the BiogeochemistryLaboratory of the Universidad Nacional de Colombia atMedellin campus The authors are grateful to A N Marın LF Osorio J C Guingue G E Mazo and N Alvarez for theirtechnical collaboration
References
[1] Y Zha and J Gao ldquoCharacteristics of desertification and itsrehabilitation in Chinardquo Journal of Arid Environments vol 37no 3 pp 419ndash432 1997
[2] J F Reynolds and D M Stafford Smith Global DesertificationDo Humans Cause Deserts Vol 88 University Press BerlinGermany 2002
[3] Plan de Accion Nacional de Lucha Contra la Desertificacion y laSequıa en Colombia (PAN) Ministerio de Ambiente Vivienday Desarrollo Territorial Bogota Colombia 2004
[4] D Celentano R A Zahawi B Finegan R Ostertag R J Coleand K D Holl ldquoLitterfall dynamics under different tropicalforest restoration strategies in Costa Ricardquo Biotropica vol 43no 3 pp 279ndash287 2011
[5] S D Reay and D A Norton ldquoAssessing the success of restora-tion plantings in a temperate New Zealand forestrdquo RestorationEcology vol 7 no 3 pp 298ndash308 1999
[6] K D Holl ldquoTropical moist forest restorationrdquo in Handbook ofEcological Restoration M R Perrow and A J Davy Eds pp539ndash558 Cambridge University Press Cambridge UK 2002
[7] J Schrautzer A Rinker K Jensen F Muller P Schwartzeand C Dier Ben ldquoSuccession and restoration of drained fensperspectives from northwestern Europerdquo in Linking Restorationand Ecological Succession L R Walker J Walker and R JHobbs Eds pp 90ndash120 Springer New York NY USA 2007
[8] R L Westerman Soil Testing and Plant Analysis Soil ScienceSociety of America Madison Wis USA 1990
[9] H Jenny S Gessel and F Bingham ldquoComparative study ofdecomposition of organic matter in temperate and tropicalregionsrdquo Soil Science vol 68 pp 419ndash432 1949
[10] J D Leon M I Gonzalez and J F Gallardo ldquoCiclos bio-geoquımicos en bosques naturales y plantaciones de conıferasen ecosistemas de alta montana de Colombiardquo Revista BiologıaTropical vol 59 pp 1883ndash1894 2011
[11] J Olson ldquoEnergy storage and balance of producers and decom-poser in ecological systemsrdquo Ecology vol 44 pp 322ndash331 1963
[12] V Meentemeyer E O Box and R Thompson ldquoWorld patternsand amounts of terrestrial plant litter productionrdquo Biosciencevol 32 pp 125ndash128 1982
[13] C Strojan F Turner and R Castetter ldquoLitter fall from shrubs inthe northernMojave desertrdquo Ecology vol 60 pp 891ndash900 1979
[14] J A Parrotta ldquoProductivity nutrient cycling and succession insingle- and mixed-species plantations of Casuarina equisetifo-lia Eucalyptus robusta and Leucaena leucocephala in PuertoRicordquo Forest Ecology andManagement vol 124 no 1 pp 45ndash771999
[15] J Goma-Tchimbakala and F Bernhard-Reversat ldquoComparisonof litter dynamics in three plantations of an indigenous timber-tree species (Terminalia superba) and a natural tropical forestin Mayombe Congordquo Forest Ecology andManagement vol 229no 1ndash3 pp 304ndash313 2006
[16] J Barlow T A Gardner L V Ferreira and C A PeresldquoLitter fall and decomposition in primary secondary andplantation forests in the Brazilian Amazonrdquo Forest Ecology andManagement vol 247 no 1ndash3 pp 91ndash97 2007
[17] K Descheemaeker B Muys J Nyssen et al ldquoLitter productionand organic matter accumulation in exclosures of the Tigrayhighlands Ethiopiardquo Forest Ecology and Management vol 233no 1 pp 21ndash35 2006
[18] J Sawyer Plantations in the Tropics Environmental ConcernsIUCN Gland Switzerland 1993
[19] A E Lugo ldquoThe apparent paradox of reestablishing speciesrichness on degraded lands with tree monoculturesrdquo ForestEcology and Management vol 99 no 1-2 pp 9ndash19 1997
[20] J F Dames M C Scholes and C J Straker ldquoLitter pro-duction and accumulation in Pinus patula plantations of theMpumalanga Province South Africardquo Plant and Soil vol 203no 2 pp 183ndash190 1998
[21] J F Dames M C Scholes and C J Straker ldquoNutrient cyclingin a Pinus patula plantation in theMpumalanga Province SouthAfricardquo Applied Soil Ecology vol 20 no 3 pp 211ndash226 2002
[22] S E Attignon D Weibel T Lachat B Sinsin P Nagel andR Peveling ldquoLeaf litter breakdown in natural and plantationforests of the Lama forest reserve in BeninrdquoApplied Soil Ecologyvol 27 no 2 pp 109ndash124 2004
[23] A N Singh A S Raghubanshi and J S Singh ldquoComparativeperformance and restoration potential of two Albizia speciesplanted onmine spoil in a dry tropical region Indiardquo EcologicalEngineering vol 22 no 2 pp 123ndash140 2004
[24] D L Moorhead and R L Sinsabaugh ldquoA theoretical model oflitter decay and microbial interactionrdquo Ecological Monographsvol 76 no 2 pp 151ndash174 2006
[25] J M Duivenvoorden and J F Lips A Land-Ecological Study ofSoils Vegetation and Plant Diversity in Colombian AmazoniaTropenbos Series 12The Tropenbos Foundation WageningenThe Netherlands 1995
[26] H Marschner Mineral Nutrition of Higher Plants AcademicPress London UK 1995
[27] R Aerts ldquoClimate leaf litter chemistry and leaf litter decompo-sition in terrestrial ecosystems a triangular relationshiprdquoOikosvol 79 no 3 pp 439ndash449 1997
[28] F J Stevenson Cycles of Soil JohnWiley amp Sons New York NYUSA 1986
[29] D Lamb andDGilmour Issues in Forest Conservation Rehabili-tation and Restoration of Degraded Forests International Unionfor Conservation of Nature and Natural Resources and WorldWide Fund Cambridge UK 2003
Table 5 Indexes calculated for return retention and release of nutrients via leaf litter in successional patches of mosquero (SPM) and forestplantations of neem (FPN) (kg haminus1 yrminus1)
Table 6 Mean values (plusmnSD) for some soil parameters (0ndash10 cm) in successional patches of mosquero (SPM) forest plantations of neem(FPN) and control sites without vegetation studied in Santafe de Antioquia (Colombia)
AE () 728 plusmn 106 685 plusmn 129 094 801 plusmn 95 110aAnalytical methods available in Westerman [8]PCI parameter change index (FPNcontrol or SPMcontrol) SOM soil organic matter ECEC effective cation exchange capacity BD bulk density ASaggregate stability lowastIndicates significant difference with control sites (Mann-Whitney P le 005)
N and P were released more slowly (lower values of119896119895
) than other nutrients and they are expected to remainlonger in the above ground leaf litter as indicated by MRTvalues (Table 5) P was released faster in FPN (119870
119895
= 068MRT = 147 years) while N was released at similar rates inboth ecosystems (119870
119895
= 057 MRT = 176 years) In bothecosystems Ca had the highest release The time necessaryfor the effective release of all elements considered in bothecosystems was 11ndash181 years
33 Soil Reclamation Soils of both SPM and FPN showedchanges of some properties with respect to soil of control sites(without vegetation) (Table 6) In SPM significant increaseswere detected with respect to the control sites on parameterssuch as soil organic matter the content (SOM) exchange-able Mg and Ca and effective cation exchange capacity(ECEC)On the other hand in FPNwere observed significantincreases in SOM totalN (Nt) available-P and exchangeable-K and significant reduction in bulk density (BD)
Despite their short period of time for both strategiesthe contributions of fine litter and its decomposition haveimproved various soil properties of these degraded landsThesharp increases of SOM observed (compared to control sites)also increased soil moisture retention capacity and soil cationexchange key aspects in the reclamation of soils of degradeddry land Although FPN showed a significant increase of P
its very low concentration in the soil determined a severeconstraint on ecosystem primary productivity
4 Conclusions
From the perspective of land restoration both modelsshowed different advantages The passive model representedby the SPM showed a higher dynamics in the reactivation ofsoil biogeochemical cycles It is expected that as the succes-sional process continues the consequently greater complexityof the ecosystem will lead to an effective improvement notonly on the soil but also on ecosystem functions On theother hand the active model represented by the FPN showedsignificant improvements in soil parameters even thoughthe returns of litter and nutrients were lower Likely thissituation is the result of differences in litter contributionswhose potential effect on soil rehabilitation has not beenfully evaluated These are issues to consider in selecting arestoration model and the degree and speed expected ofthe degradation process Thus an active model should beconsideredwhen the rate of degradation of the area of interestis high because the planted species can be established quicklyand create better conditions for a more diverse biologicalcommunity as pointed by [5] When the state and rate ofdegradation are not severe themost appropriatemodelmightbe the passive restoration allowing the ecosystem a natural
6 ISRN Soil Science
recover [29] which had advantages from ecological andeconomic perspectives
Acknowledgments
The authors thank the Direction of Research of the Universi-dadNacional de Colombia for financial support of the ProjectldquoRestoration of lands in a process of desertificationwith neemplantations (Azadirachta indica) in Western Antioquiardquo JuanD Leon was supported by Convocatoria Nacional de Investi-gacion y de Creacion Artıstica de la Universidad Nacional deColombia 2010ndash2012 They also thank the BiogeochemistryLaboratory of the Universidad Nacional de Colombia atMedellin campus The authors are grateful to A N Marın LF Osorio J C Guingue G E Mazo and N Alvarez for theirtechnical collaboration
References
[1] Y Zha and J Gao ldquoCharacteristics of desertification and itsrehabilitation in Chinardquo Journal of Arid Environments vol 37no 3 pp 419ndash432 1997
[2] J F Reynolds and D M Stafford Smith Global DesertificationDo Humans Cause Deserts Vol 88 University Press BerlinGermany 2002
[3] Plan de Accion Nacional de Lucha Contra la Desertificacion y laSequıa en Colombia (PAN) Ministerio de Ambiente Vivienday Desarrollo Territorial Bogota Colombia 2004
[4] D Celentano R A Zahawi B Finegan R Ostertag R J Coleand K D Holl ldquoLitterfall dynamics under different tropicalforest restoration strategies in Costa Ricardquo Biotropica vol 43no 3 pp 279ndash287 2011
[5] S D Reay and D A Norton ldquoAssessing the success of restora-tion plantings in a temperate New Zealand forestrdquo RestorationEcology vol 7 no 3 pp 298ndash308 1999
[6] K D Holl ldquoTropical moist forest restorationrdquo in Handbook ofEcological Restoration M R Perrow and A J Davy Eds pp539ndash558 Cambridge University Press Cambridge UK 2002
[7] J Schrautzer A Rinker K Jensen F Muller P Schwartzeand C Dier Ben ldquoSuccession and restoration of drained fensperspectives from northwestern Europerdquo in Linking Restorationand Ecological Succession L R Walker J Walker and R JHobbs Eds pp 90ndash120 Springer New York NY USA 2007
[8] R L Westerman Soil Testing and Plant Analysis Soil ScienceSociety of America Madison Wis USA 1990
[9] H Jenny S Gessel and F Bingham ldquoComparative study ofdecomposition of organic matter in temperate and tropicalregionsrdquo Soil Science vol 68 pp 419ndash432 1949
[10] J D Leon M I Gonzalez and J F Gallardo ldquoCiclos bio-geoquımicos en bosques naturales y plantaciones de conıferasen ecosistemas de alta montana de Colombiardquo Revista BiologıaTropical vol 59 pp 1883ndash1894 2011
[11] J Olson ldquoEnergy storage and balance of producers and decom-poser in ecological systemsrdquo Ecology vol 44 pp 322ndash331 1963
[12] V Meentemeyer E O Box and R Thompson ldquoWorld patternsand amounts of terrestrial plant litter productionrdquo Biosciencevol 32 pp 125ndash128 1982
[13] C Strojan F Turner and R Castetter ldquoLitter fall from shrubs inthe northernMojave desertrdquo Ecology vol 60 pp 891ndash900 1979
[14] J A Parrotta ldquoProductivity nutrient cycling and succession insingle- and mixed-species plantations of Casuarina equisetifo-lia Eucalyptus robusta and Leucaena leucocephala in PuertoRicordquo Forest Ecology andManagement vol 124 no 1 pp 45ndash771999
[15] J Goma-Tchimbakala and F Bernhard-Reversat ldquoComparisonof litter dynamics in three plantations of an indigenous timber-tree species (Terminalia superba) and a natural tropical forestin Mayombe Congordquo Forest Ecology andManagement vol 229no 1ndash3 pp 304ndash313 2006
[16] J Barlow T A Gardner L V Ferreira and C A PeresldquoLitter fall and decomposition in primary secondary andplantation forests in the Brazilian Amazonrdquo Forest Ecology andManagement vol 247 no 1ndash3 pp 91ndash97 2007
[17] K Descheemaeker B Muys J Nyssen et al ldquoLitter productionand organic matter accumulation in exclosures of the Tigrayhighlands Ethiopiardquo Forest Ecology and Management vol 233no 1 pp 21ndash35 2006
[18] J Sawyer Plantations in the Tropics Environmental ConcernsIUCN Gland Switzerland 1993
[19] A E Lugo ldquoThe apparent paradox of reestablishing speciesrichness on degraded lands with tree monoculturesrdquo ForestEcology and Management vol 99 no 1-2 pp 9ndash19 1997
[20] J F Dames M C Scholes and C J Straker ldquoLitter pro-duction and accumulation in Pinus patula plantations of theMpumalanga Province South Africardquo Plant and Soil vol 203no 2 pp 183ndash190 1998
[21] J F Dames M C Scholes and C J Straker ldquoNutrient cyclingin a Pinus patula plantation in theMpumalanga Province SouthAfricardquo Applied Soil Ecology vol 20 no 3 pp 211ndash226 2002
[22] S E Attignon D Weibel T Lachat B Sinsin P Nagel andR Peveling ldquoLeaf litter breakdown in natural and plantationforests of the Lama forest reserve in BeninrdquoApplied Soil Ecologyvol 27 no 2 pp 109ndash124 2004
[23] A N Singh A S Raghubanshi and J S Singh ldquoComparativeperformance and restoration potential of two Albizia speciesplanted onmine spoil in a dry tropical region Indiardquo EcologicalEngineering vol 22 no 2 pp 123ndash140 2004
[24] D L Moorhead and R L Sinsabaugh ldquoA theoretical model oflitter decay and microbial interactionrdquo Ecological Monographsvol 76 no 2 pp 151ndash174 2006
[25] J M Duivenvoorden and J F Lips A Land-Ecological Study ofSoils Vegetation and Plant Diversity in Colombian AmazoniaTropenbos Series 12The Tropenbos Foundation WageningenThe Netherlands 1995
[26] H Marschner Mineral Nutrition of Higher Plants AcademicPress London UK 1995
[27] R Aerts ldquoClimate leaf litter chemistry and leaf litter decompo-sition in terrestrial ecosystems a triangular relationshiprdquoOikosvol 79 no 3 pp 439ndash449 1997
[28] F J Stevenson Cycles of Soil JohnWiley amp Sons New York NYUSA 1986
[29] D Lamb andDGilmour Issues in Forest Conservation Rehabili-tation and Restoration of Degraded Forests International Unionfor Conservation of Nature and Natural Resources and WorldWide Fund Cambridge UK 2003
recover [29] which had advantages from ecological andeconomic perspectives
Acknowledgments
The authors thank the Direction of Research of the Universi-dadNacional de Colombia for financial support of the ProjectldquoRestoration of lands in a process of desertificationwith neemplantations (Azadirachta indica) in Western Antioquiardquo JuanD Leon was supported by Convocatoria Nacional de Investi-gacion y de Creacion Artıstica de la Universidad Nacional deColombia 2010ndash2012 They also thank the BiogeochemistryLaboratory of the Universidad Nacional de Colombia atMedellin campus The authors are grateful to A N Marın LF Osorio J C Guingue G E Mazo and N Alvarez for theirtechnical collaboration
References
[1] Y Zha and J Gao ldquoCharacteristics of desertification and itsrehabilitation in Chinardquo Journal of Arid Environments vol 37no 3 pp 419ndash432 1997
[2] J F Reynolds and D M Stafford Smith Global DesertificationDo Humans Cause Deserts Vol 88 University Press BerlinGermany 2002
[3] Plan de Accion Nacional de Lucha Contra la Desertificacion y laSequıa en Colombia (PAN) Ministerio de Ambiente Vivienday Desarrollo Territorial Bogota Colombia 2004
[4] D Celentano R A Zahawi B Finegan R Ostertag R J Coleand K D Holl ldquoLitterfall dynamics under different tropicalforest restoration strategies in Costa Ricardquo Biotropica vol 43no 3 pp 279ndash287 2011
[5] S D Reay and D A Norton ldquoAssessing the success of restora-tion plantings in a temperate New Zealand forestrdquo RestorationEcology vol 7 no 3 pp 298ndash308 1999
[6] K D Holl ldquoTropical moist forest restorationrdquo in Handbook ofEcological Restoration M R Perrow and A J Davy Eds pp539ndash558 Cambridge University Press Cambridge UK 2002
[7] J Schrautzer A Rinker K Jensen F Muller P Schwartzeand C Dier Ben ldquoSuccession and restoration of drained fensperspectives from northwestern Europerdquo in Linking Restorationand Ecological Succession L R Walker J Walker and R JHobbs Eds pp 90ndash120 Springer New York NY USA 2007
[8] R L Westerman Soil Testing and Plant Analysis Soil ScienceSociety of America Madison Wis USA 1990
[9] H Jenny S Gessel and F Bingham ldquoComparative study ofdecomposition of organic matter in temperate and tropicalregionsrdquo Soil Science vol 68 pp 419ndash432 1949
[10] J D Leon M I Gonzalez and J F Gallardo ldquoCiclos bio-geoquımicos en bosques naturales y plantaciones de conıferasen ecosistemas de alta montana de Colombiardquo Revista BiologıaTropical vol 59 pp 1883ndash1894 2011
[11] J Olson ldquoEnergy storage and balance of producers and decom-poser in ecological systemsrdquo Ecology vol 44 pp 322ndash331 1963
[12] V Meentemeyer E O Box and R Thompson ldquoWorld patternsand amounts of terrestrial plant litter productionrdquo Biosciencevol 32 pp 125ndash128 1982
[13] C Strojan F Turner and R Castetter ldquoLitter fall from shrubs inthe northernMojave desertrdquo Ecology vol 60 pp 891ndash900 1979
[14] J A Parrotta ldquoProductivity nutrient cycling and succession insingle- and mixed-species plantations of Casuarina equisetifo-lia Eucalyptus robusta and Leucaena leucocephala in PuertoRicordquo Forest Ecology andManagement vol 124 no 1 pp 45ndash771999
[15] J Goma-Tchimbakala and F Bernhard-Reversat ldquoComparisonof litter dynamics in three plantations of an indigenous timber-tree species (Terminalia superba) and a natural tropical forestin Mayombe Congordquo Forest Ecology andManagement vol 229no 1ndash3 pp 304ndash313 2006
[16] J Barlow T A Gardner L V Ferreira and C A PeresldquoLitter fall and decomposition in primary secondary andplantation forests in the Brazilian Amazonrdquo Forest Ecology andManagement vol 247 no 1ndash3 pp 91ndash97 2007
[17] K Descheemaeker B Muys J Nyssen et al ldquoLitter productionand organic matter accumulation in exclosures of the Tigrayhighlands Ethiopiardquo Forest Ecology and Management vol 233no 1 pp 21ndash35 2006
[18] J Sawyer Plantations in the Tropics Environmental ConcernsIUCN Gland Switzerland 1993
[19] A E Lugo ldquoThe apparent paradox of reestablishing speciesrichness on degraded lands with tree monoculturesrdquo ForestEcology and Management vol 99 no 1-2 pp 9ndash19 1997
[20] J F Dames M C Scholes and C J Straker ldquoLitter pro-duction and accumulation in Pinus patula plantations of theMpumalanga Province South Africardquo Plant and Soil vol 203no 2 pp 183ndash190 1998
[21] J F Dames M C Scholes and C J Straker ldquoNutrient cyclingin a Pinus patula plantation in theMpumalanga Province SouthAfricardquo Applied Soil Ecology vol 20 no 3 pp 211ndash226 2002
[22] S E Attignon D Weibel T Lachat B Sinsin P Nagel andR Peveling ldquoLeaf litter breakdown in natural and plantationforests of the Lama forest reserve in BeninrdquoApplied Soil Ecologyvol 27 no 2 pp 109ndash124 2004
[23] A N Singh A S Raghubanshi and J S Singh ldquoComparativeperformance and restoration potential of two Albizia speciesplanted onmine spoil in a dry tropical region Indiardquo EcologicalEngineering vol 22 no 2 pp 123ndash140 2004
[24] D L Moorhead and R L Sinsabaugh ldquoA theoretical model oflitter decay and microbial interactionrdquo Ecological Monographsvol 76 no 2 pp 151ndash174 2006
[25] J M Duivenvoorden and J F Lips A Land-Ecological Study ofSoils Vegetation and Plant Diversity in Colombian AmazoniaTropenbos Series 12The Tropenbos Foundation WageningenThe Netherlands 1995
[26] H Marschner Mineral Nutrition of Higher Plants AcademicPress London UK 1995
[27] R Aerts ldquoClimate leaf litter chemistry and leaf litter decompo-sition in terrestrial ecosystems a triangular relationshiprdquoOikosvol 79 no 3 pp 439ndash449 1997
[28] F J Stevenson Cycles of Soil JohnWiley amp Sons New York NYUSA 1986
[29] D Lamb andDGilmour Issues in Forest Conservation Rehabili-tation and Restoration of Degraded Forests International Unionfor Conservation of Nature and Natural Resources and WorldWide Fund Cambridge UK 2003
