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THINKING beyond the canopy
Soil dynamics in tropical forest transition: a case study from Borneo, Indonesia
[Imam Basuki and Yves Laumonier][July, 22nd 2014 – Cairns, Australia]
THINKING beyond the canopy
Few studies had been conducted in
SEA on deforestation’s impact on soils.
The research hypothesized that
deforestation and forest degradation
have decreased performance of soil
function such as fertility, water
regulation and sequestration of GHG.
Introduction
THINKING beyond the canopy
Methods Site selection considered: slope ≥ 40%, slope position (up,
mid, bottom), and distance to primary forests 33 sites. Soil samples were collected from 5 LUs, i.e., the primary
forest and the adjacent logged over forests, rice field, fallow, and rubber garden. Lab. analyses on soil physical and chemical properties.
THINKING beyond the canopy
Results
THINKING beyond the canopy
Status of soil surface characteristics by land types
-------------------------------- Land type (N) -----------------------------------
Soil characteristics
Primary Forest (12)
Logged Forest (8)
Upland rice (5)
Fallow (4)
Rubber (4)
CEC (me/100g) L - M VL - L L VL VLBase Saturation (%) VL VL VL - L L LP2O5 (ppm) VL - M VL VL VL VL
K2O (ppm) M - VH L - VH M - VH VH M - VHC (%) L - VH VL - M VL - H VL - H VL - LN (%) L - M VL - L VL - M VL - M VL - LC/N M - H M M M L - MK+ (me/100g) VL - L VL - L VL - M L - M VL - LNa+ (me/100g) VL - L VL - L VL - L VL - L VLMg2+ (me/100g) VL VL VL - L VL VLCa2+ (me/100g) VL VL VL VL VLAl3+ (me/100g) VL VL VL VL VL
THINKING beyond the canopy
Stock changes on mean carbon and exchangeable cations in the soil surface
Land-use Soil layer
Change in stocks of soil carbon and exchangeable cations (kg/ha)
C N P2O5 Ca2+ Mg2+ K+ Na+ Al3+
Primary forest (PF)
1 *45422.88 *3370.96 *9.06 *101.51 *44.74 *72.95 *30.94 *668.45
2 *15560.84 *1266.95 *4.26 *121.39 *35.83 *32.45 *26.70 *448.93
Logged over forest (LF) 1 -18884.48 -1300.42 -2.74 +20.40 -1.20 -14.33 +4.46 -104.84
2 +1606.46 +100.98 +1.11 +31.61 +0.51 +2.79 -0.88 +87.50Upland rice (UR)
1 -6000.09 -186.54 -1.70 +66.83 +15.22 +22.75 +9.04 -111.912 +898.69 +130.13 -0.11 +63.05 +12.87 +19.91 +5.19 -121.46
Fallow (FL)
1 -20256.88 -1035.46 -6.02 +27.36 +9.91 +26.11 +6.37 -381.692 +6828.16 +760.55 -1.71 +10.20 +9.72 +31.32 -10.43 -265.36
Rubber (RB)
1 -29969.38 -1910.96 -5.97 +69.57 +12.44 -2.98 -13.99 -405.332 +13550.66 +1353.55 -1.96 +79.68 +11.39 +37.34 -6.92 -130.29
(*) : original stock (-) : lost stock; (+) : gained stock
THINKING beyond the canopy
Soil fertility and water availability
Logging activities and forest conversion to agriculture land decreased soil fertility in the research area.
Forest conversion into upland rice, fallow and rubber garden had increased the infiltration rate of surface soil and percentage of macro pores.
Logging activities had increased soil bulk density and decreased the soil macro porosity as well as infiltration rate.
THINKING beyond the canopy
Carbon and Nitrogen loss
Soil organic carbon stock had decreased from primary to logged over forests, upland rice, fallow and rubber garden by -18.8 Mg/ha (-42%), -6.0 Mg/ha (-13%), -20.3 Mg/ha (-54%) and -30.0 Mg/ha (-66%) respectively.
Soil nitrogen had also decreased by -1.3 Mg/ha (-39%) in LF, -0.2 Mg/ha (-6%) in UR, -1.0 Mg/ha (-31%) in FL and -1.9 Mg/ha (-57%) in RB.
THINKING beyond the canopy
Deforestation deplete soil-Al3+
Al3+
(cm
ol/k
g)
a. Clay (%) b. P2O5 (ppm)
THINKING beyond the canopy
Conclusion
Logging activities and forest conversion to agriculture-land decrease soil fertility in the research area.
Moreover, those activities can increase runoff, soil erosion and further released the carbon and nitrogen stocks from soils.
Logging should be totally banned on the steep slopes and soil conservation techniques are needed to sustain a more productive and responsible agriculture.
THINKING beyond the canopy
Acknowledgement
Authors would like to express gratitude to research partners particularly Riak Bumi foundation that provided logistical and technical supports during the research.
We appreciate all the helps and trusts from local people in Keluin longhouse and local government in Kapuas Hulu District, West Kalimantan, Indonesia.
We also express sincere thanks to the Europian Union for funding this research, and to CIFOR CRP-6 Component 3 for financial supports.