Article history:Received 30 May 2013Received in revised form 17 January 2014Accepted 28 January 2014Available online 28 February 2014
Keywords:Headwater areaTriggering eventsExposed rootsEarlywood and latewood anatomy
Local, short-lasting downpour is typically observed more frequently in headwater areas than in overall catch-ments. Headwater systems act as buffers and serve as starting points for stream channels. Therefore, recognitionof the magnitude and frequency of their transformation is important for the understanding of the functioning ofentire mountain catchments. Despite numerous studies on extreme events, the headwater areas are still poorlyrecognised. There are a number of steep forest-covered headwater areas in the Gorce Mountains, a range offlysch-type mountains that form part of the Polish Carpathians, which have not yet been studied in relationto this issue. Therefore, the main aim of this study was to determine the nature of geomorphic activity actingwithin different parts of the headwater areas. In order to date extreme geomorphic events precisely, adendrogeomorphic approach was performed based on anatomical changes in exposed roots. A total of 59 sprucePicea abies L. Karst roots were sampled. Besides the reduction in tracheid lumen area in earlywood that is tradi-tionally used, a recently developed approach using an abrupt change in the amount of latewood as an indicationof themomentwhen geomorphic activity takes placewas also taken into consideration. Data from exposed rootswere compared to rainfall data. The results showed that the headwater areas experienced a variety of geomor-phic processes. The timing of processes was assessed for the years 1944 to 2001. The main difference betweenthe roots can be observed between the upper and lower parts of the headwater area. In the upper part of theheadwater area, anatomical changes within the roots were observed when heavy rainfall events occurred, i.e.in 1958, 1970, 1971, 1972, and 1985. Roots in the lower part of the headwater area had become exposed duringcontinuous rainfalls in 1997 and 2001. This research provides a fundamental review of dendrogeomorphologicalmethodology applied to the identification of extreme geomorphic events acting within headwater areas.
Extreme geomorphic events in the flysch-typemountains have beenexamined many times and by a number of different researchers (Ellenand Wieczorek, 1988; Froehlich and Starkel, 1995; Gil and Starkel,1979; Jacobson et al., 1989; Kotarba, 1998; Nemčok, 1982; Šilhán andPánek, 2010; Starkel, 1979, 1996, 2002). Such events typically followthe magnitude–frequency relationship in that they are episodic buttheir magnitude may be very high. They tend to scour channels, trans-form the headwater areas and produce abrupt changes in mountainrelief (Benda, 1990; Crozier, 1986; Dietrich and Dunne, 1978; Kelsey,1980; Ziętara, 1968). These kinds of events are mainly induced by rain-fall. Starkel (1979, 1996, 2002) classified rainfalls into three differenttypes. Each of these rainfall types possesses different levels of geomor-phic effectiveness and is characterised by a different threshold value:i) local, short-lasting downpours are morphologically effective in smallcatchments, tend to produce debris flows and mudflows, amount to30–120 mm and have an intensity of 1–3 mm/min, ii) continuous rainis morphologically effective when precipitation does not exceed 3–12mm/h and reaches a quantity of between 150 and 400mmover a periodof 2–5 days, and iii) rainy seasons occur when precipitation during thesummer months reaches 200–500 mm.
Local, short-lasting downpours are typically observed morefrequently in headwater systems than in overall catchments. Thoseremote areas are located in the upper parts of mountain catchments(Gomi et al., 2002; Montgomery and Dietrich, 1988). Gomi et al.(2002) highlighted the fact that headwater areas, understood as zero-order basins, make a hydrological contribution to first-order andsecond-order channel discharge. Furthermore, there exists a very closerelationship between hydrological and geomorphic processes withinheadwater areas where water input exerts a significant influence onhillslope and channel conditions (Sidle et al., 2000). For this reason, anunderstanding of the functioning of headwater systems is crucial tothe understanding of systems covering entire mountain catchments.
Much previous research concerning the activity of headwater areaswas carried out post factum, based on geomorphological mapping inthe field (Crozier, 1986; Ellen and Wieczorek, 1988; Jacobson et al.,1989). Application of this method does not allow one to determinethe frequency ofmorphogenetic processes and does not allow one to as-sess the role of the particular events in the headwater system. Informa-tion gathered could refer to different geomorphological events whichtend to cluster during consecutive years (Starkel, 2006). In addition,Starkel (2012) emphasised thatmanyworldwide correlations of rainfalldata with their geomorphic consequences were based on data obtainedfrom a distant (even exceeding 15 km distant) recording station andwere thus not sufficiently reliable to draw conclusions. Headwaterareas are usually poorly instrumented therefore, studies which are lo-cated in such areas close to a meteorological station (less than 1 km)are of great interest for the understanding of how such areas function.
Dendrogeomorphologicalmethods are currently used to reconstructa variety of geomorphic processes (Alestalo, 1971; Bollschweiler et al.,2007; Carrara and Carroll, 1979; Pelfini and Santilli, 2008; Stoffel,2006; Zielonka et al., 2008). Changes in root structure caused by asudden or continuous exposure to the atmosphere have proven to bea helpful tool in geomorphology (Gärtner, 2003, 2006, 2007; Gärtneret al., 2001; Schweingruber, 1996).
Measurements of gradual changes taking placewithin roots are usedto calculate soil and sheet erosion (Bodoque et al., 2005, 2011; Buchwał,2008; Corona et al., 2011; Pelfini and Santilli, 2006; Pérez-Rodríqueset al., 2007; Rubíales et al., 2008; Saez et al., 2011; Wrońska-Wałach,2009). Dendrogeomorphological methods are being tested in differentconditions for their accuracy and usefulness in dating and quantifyingof soil erosion (Ballesteros-Cánovas et al., 2013; Corona et al., 2011;Saez et al., 2011). Ballesteros-Cánovas et al. (2013) emphasised the im-portance of precise measurements of microtopography around roots inthe quantifying of erosion rates by using dendrogeomorphological
methods and proved that dendrogeomorphological analysis is helpfulfor the reconstruction of extreme events and erosion in badlands.Furthermore, changes in cell structure in the roots of various treespecies are used to reconstruct the frequency of extreme events actingin different environments (Hitz et al., 2008; Malik, 2008; Malik andMatyja, 2008). Nevertheless, there still exists a data deficit relating tothe potential benefits of the application of dendrogeomorphologicalanalysis to the evaluation of the role of extreme geomorphic events inheadwater areas in midsize mountain ecosystems.
Data obtained from such analysis yield insight into the role of differ-ent rainfall events in the development of headwater areas in midsizemountains. Moreover, the type of data obtained by analysing exposedroots can be crucial to the understanding of:
- geomorphological processes affecting different parts of headwaterareas
- various geomorphic processes overlapping with different types ofprecipitation
- the role of headwater areas as buffer zones between slopes andchannel systems.
The aim of the studywas to connect various anatomical responses ofexposed spruce (Picea abies L. Karst) roots to geomorphic processes atthree levels of magnitude–frequency (M–F) relationships: episodic butwith high magnitude, moderate M–F and continuous. Subsequently,based on that link, a description was made of geomorphic activity inan area which is located close (less than 1 km) to the meteorologicalstation and thus could exhibit a reliable relationship between rainfalland different geomorphic processes within the headwater area.
2. Study area
Fieldwork was carried out in the Gorce Mountains (Polish flysch-type Carpathians). The GorceMountains are built of a lithostratigraphicunit in the flysch called the Magura nappe. With an elevation of1200–1300 m a.s.l. and a slope gradient of more than 20°, they are rep-resentative of midsize mountains (Klimaszewski, 1972; Starkel, 1996).
The study area is located within the Gorce National Park on thesouthern edge of the Gorce Mountains and features a number of steepforest-covered headwater catchments (Fig. 1). The headwaters in thisarea exhibit fresh signs of contemporary geomorphic activity.The Olszowy headwater area, featuring a well-preserved semi-naturalforest, was selected for analysis (Fig. 1).
In the study headwater area landforms indicative of a past landslideoccur such as 20–50 m high headwalls, sloping at 30–45°, displacedblocks, and a distinct toe (Fig. 1-B). The headwater taken into consider-ation has a drainage basin area of 0.62 km2, a drainage density of about7.03 km/km2, and mean slope of 25–30°. The most diverse area is theupper part of the headwater catchment where small gully-type valleys,rills, rock veneers (a thin accumulation of rock clasts that partially orfully covers a surface or hillslope), torrential chutes, and small landslidescars can be found close to one another. Further down the headwaterarea one comes across a landslide toe which is dissected by ravine-type and V-shaped valleys.
TheOlszowy headwater area is covered by subalpine spruce forest inits terminal phase of development (Chwistek, 2001). The density ofNorway spruce (P. abies) is similar throughout the entire study areaand ranges from 7.1 to 8.0 trees/100 m2 (Loch et al., 2001).
The climate of the GorceMountains is characterised by the presenceof several climate zones. Mean annual temperature in the altitudinalprofile ranges from 6 to 7 °C in the foothills to about 3 °C on mountainridges (Hess, 1965). Average annual precipitation ranges from 750 to800 mm at lower elevations to 1200 mm on the upper part of theridge. The maximum monthly precipitation is in July and August. Fourdifferent plots were chosen for further analysis.
The first plot analysed is located in the upper part of the headwaterarea and starts above the landslide niche, close to a man-made forest
Fig. 1. Localization of study area; A: 1 — approximated localization of meteorological stations, 2 — approximated extension of Gorce National Park, 3 — study area; B: Geomorphologicaloutline of Olszowy headwater area (four rectangles indicate the four plots listed in the text).
43D. Wrońska-Wałach / Catena 118 (2014) 41–54
boundary (about 1220m a.s.l.). It is a 100m long, discontinuous torren-tial channel, with steps generally having developed on top of scarred ordamaged roots. It terminates at the end of the slide block with a widetorrential fan (Fig. 1-B, Rectangle 1).
The second plot is located within the landform in the upper part ofthe headwater area (elevation: about 1180 m), parallel to the first andabout 35 m to the west. It starts at the bottom of the landslide nicheas a small hollow and changes 10 m downward into a 3–4 m widerock veneer. Further down, it transforms into a 0.5 m deep and 0.8 mwide small gully-like valley (Fig. 1-B, Rectangle 2).
The third plot is located in themiddle part of the headwater area. It isa shallow discontinuous gully characterised by a variable transversalprofile (Fig. 1-B, Rectangle 3).
The fourth plot is located in the lower part of the headwater. It is aravine-like tributary valley hanging over the main V-shaped valley(Fig. 1-B, Rectangle 4). The landform analysed is about 1–2 m wideand between 1.5 and 3.0 m deep. It possesses feature characteristic ofthis type of valley such as a step-pool longitudinal profile with steps
developing either on rock debris or woody debris. The ravine alsoshows signs of lateral undercutting about 0.5–1.5 m high.
3. Materials and methods
Detailed geomorphological mappingwas performed in the headwa-ter area selected. A preliminary investigation produced landforms withdistinct and fresh boundaries for further analysis. Furthermore, selectedlandforms such as landslide scars, gullies, torrential channels, rills,and rock veneers were inspected for the presence of exposed rootswith particular attention paid to scarred roots.
Detailed measurements of the position of exposed roots were pro-duced using GPS — Garmin 60 CSx and Kestrel 4000. Landforms featur-ing exposed roots were taken into consideration. Morphometricparameters such as landform length, width, and depth were obtained.On the basis of detailed geomorphological mapping, the geomorphicprocesses that had caused exposure were also initially determined.
44 D. Wrońska-Wałach / Catena 118 (2014) 41–54
Transverse profiles were obtained every 50 m for each landformanalysed as well as for each site with exposed roots.
Root samples were collected from four different plots. The plots of in-terest were selected in order to investigate different types of geomorphicprocess related to rainfall events (Fig. 1-B). Detailedmapping of root loca-tions at specific plots included the precisemeasurement of the distance ofroots from the soil surface as well as from the side of the landform. Discswere obtained from 59 exposed roots of 22 spruce trees (P. abies). Rootsamples were taken at a minimum distance of about 1 m from the stemin order to exclude disturbances caused by the stem (LaMarche, 1968).
Tree root features are wedging, missing and double rings. Therefore,to identifymissing or double rings and to date the age of roots precisely,a reference chronology was constructed. Visual cross-dating and serialsectioning which are commonly used for dating shrubs (Buchwałet al., 2013; Kolishchuk, 1990) were taken into consideration(Wrońska-Wałach et al., 2012, 2014). From each root there were fourdiscs taken at a distance of 2 cm from each other. Cross sections of theroot discs as well as micro sections were prepared, polished andscanned in the 3200 dpi (Epson Perfection V700). The prepared piecesof wood were then cut into 15–20 μm slides using a sledge-microtome“GSL 1” and stained according to the procedure developed bySchweingruber (1990). Images of the prepared slides were madeusing a Nikon camera. Tree ring width measurements were performedusingWinDENDRO (Regent). Growth curveswere obtained based on vi-sual cross-dating between four radii of a single complete cross-sectionwithin the root and a subsequent comparison of the growth curves ob-tained from the different cross-sections to detect wedging rings in thelongitudinal profile. The second stage comprised cross-dating betweenthe root growth curves (Wrońska-Wałach et al., 2014).
A reference chronologywas prepared fromunexposed parts of the 10oldest spruce roots from all the plots used in the analysis. The resultinggrowth curves of 49 conifer roots were cross-dated via the referencechronology in order to ensure correct dating of samples. The referencechronology as well as cross-dating was calculated in WinDENDRO. Thechronology was too short and did not permit a reasonable degree ofstatistical correlation using COFECHA (Holmes, 1983) therefore thecorrelation coefficient known as the “Gleichlaufigkeit sign test” (Gl)was used (Regent 2009 after Huber, 1943; Schweingruber, 1988) forthe purpose of cross-dating the roots and the series has been visuallycross-dated in WinDENDRO.
The structural changes in roots were examined viameasurements ofcell lumen areas using WinCELLPro (Regent) in order to reconstructgeomorphic processes taking place during different types of rainfallevent. Spruce root samples were rigorously examined with special at-tention beingpaid to changes in earlywood (EW) lumen size and chang-es in the percentage of latewood (LW) present in succeeding tree-rings.Reduced EW cell size of the order of 50–60% or more below normal wasconsidered a key indicator of root exposure (Gärtner, 2003, 2007;Gärtner et al., 2001). Furthermore, abrupt and gradual changes in thepercentage of LW within the tree ring were considered a sign of differ-ent geomorphic activities in the headwater area of interest. Until nowmany researchers described some LW changes in anatomy as signs ofprogressive erosion leading to the eventual exposure of roots (Coronaet al., 2011; Gärtner, 2003; Rubíales et al., 2008). The reduction of soilcover can be induced by bothmoderateM–F slopewash and continuousdenudation. Changes in the thickness of LW tracheids and tree-ringwidth also occur within roots which are exposed to piping (Wrońska-Wałach et al., 2014). Therefore, the modifications in LW were also con-sidered amark of geomorphic activity. The amount of LWwasmeasuredwithWinCELL using the path analysis classification (Regent after Denne,1988). According to this procedure, a LW cell is a cell in which twice thetotal wall thickness is larger or equal to lumen length:
2 � aþ cð Þ≥b
where: a, c — wall thickness and b — lumen length.
A path analysis was performed to identify changes in the totalamount of LWwithin the tree-ring, and abrupt change of the percentageof EW/LWwas taken into consideration.
The data obtained from WinCell analysis were subjected to simplestatistical analysis. Data are normal therefore a Pearson's correlation be-tween the structural changes in the roots and the rainfall data fromRabka and Turbacz stations was performed. Changes in the anatomyof both EW and LW in the conifer root were considered in order toassess hydro-geomorphological activity in the headwater area.
The resulting data were then compared with available rainfall datarecorded at meteorological stations in Turbacz and Rabka. The TurbaczStation is the mountain station and is located, about 800–900 m awayfrom the study area. Its precipitation data cover the period from 1956to 1981 (its period of operation). Data from the Rabka station (about 9km away), cover the period from 1955 to 2007. Rabka station is locatedin a valley. Data from both stations were used in the analysis. The totalprecipitation correlation between the two stations is 0.86 and is statisti-cally significant. The maximum daily precipitation correlation betweenthe two stations is 0.38.Weather parameters such asmonthly precipita-tion for the June–September period as well as the highest 24-hourprecipitation amount in each given year were taken into consideration.
4. Results
A 78-year long (1930–2008) spruce root chronology was establishedbased on 10 roots from the four study plots. The mean ring-width was0.30 mm. The average correlation between the root growth curvesfrom different plots was Gl = 52. The average correlation between rootring-width growth curves within one site was higher and overall Gl =62. The highest correlation (Gl = 78) was obtained for the crossdatingof the reference chronology with the unexposed part of roots. The miss-ing values were detected for the rings formed after the exposure event.
The year of exposure varied significantly occurring at different timesduring the period from 1944 to 2001. On average, changes in the rootstructure caused by exposure or continuous denudation of the surfacelayer occurred every 2–3 years (Fig. 3). However, the types of suddenchanges in root structure,which are relevant for the reconstruction of ex-treme events occurred every 10–12 years. In terms of anatomical chang-es reported by different researchers, three types of geomorphologicallyactive processes were indicated (Table 1).
The largest number of roots analysed, more than 33% of the totalsamples, had been exposed (63.3%) or brought closer to the surfacedue to moderate M–F slope wash or continuous denudation (36.6%)during the period from 1983 to 1984 (Fig. 2). In total 60% of these orig-inated from the upper part of the headwater area (Plot 1 and 2) (Figs. 2,3, 4). A second period representingmore than 21% of the roots analysedwas the period from 1970 to 1972. During that time period, it wasmainly roots in the upper part of the headwater area that had becomeexposed (79%) or brought closer to the surface. By contrast, a majorexposure event had been registered in 1997 (63%) affecting roots inthe lower and middle part of the headwater area. No missing ringswere found from the samples taken from these plots.
4.1. Plot 1
The root samples collected from the first plot had become exposedand brought closer to the surface in several stages (Table 2; Figs. 2, 4).The first period of anatomical changes had been between 1947 and1953when continuous denudation occurred as indicated bywood anat-omy changes (Figs. 2, 3; Table 1). In 1958 two root samples had anatom-ical changes of the second type. Samples collected from the upperreaches and steps along the torrential channel had become exposed inthe period from 1970 to1972. They had anatomical changes of the firsttype (Tables 1, 2; Fig. 3). The typical situation observedwas a significantincrease in the number of LW cells one year before the reduction in thelumen area of EW tracheids (Fig. 2A, D). One of the roots displayed
Fig. 2. Geomorphological map of site one (torrential channel with torrential fan). Example of graphs showing annual variation of the mean lumen area size of earlywood (black line) andthe changes in the percentage of LW (grey columns) of particular roots locatedwithin the torrential channel A—O_83; B— O_82; C—O_81; and D— O_76. Black arrows indicate the firsttree rings after the exposure (Wrońska-Wałach, 2009 — modified).
45D. Wrońska-Wałach / Catena 118 (2014) 41–54
changes of the second type during the period from 1970 to 1973 withsubsequent anatomical changes of the first type in 1983 (Fig. 2C). Theroots exposed during the period from 1970 to 1972 are found togetherwith roots which had either become exposed (6 samples) or scarred (9samples) at the end of the growing season in 1983 (Table 2; Fig. 3).Reduction of the EW cell lumen size was observed for the followingyear (Fig. 4). Roots exposed in 1983 appeared in the lower part of thetorrential channel and in the central part of the deposition fan.
4.2. Plot 2
The earliest date for root exposure in the secondplotwas establishedto be 1944. Anatomical changes of the first type were found on a rootspanning from one side of a gully-like valley to the other (Tables 1, 3;Fig. 5-O_3). The events that caused exposure of roots in the secondplot had only occurred six times between 1944 and 2000. Four timeperiods were identified, during which roots had become fully exposedor the thickness of soil cover had become reduced due to geomorpho-logical activity via different processes. The first period of anatomicalchange in roots was registered from 1968 to 1972 (Figs. 3, 5). Duringthat period soil from five roots was removed (changes of the firsttype) and four rootswere subject tomoderateM–F slopewash or piping(changes of the second type). The second period of root exposure wasbetween 1978 and 1979. During that period the next three roots wereexposed and six were brought closer to the surface (Fig. 3 — Plot 2).Samples taken from rock veneer and from the slope exhibited changesof both the second and third types (Tables 1, 2). Most of roots from
the second plot were exposed, during the third period, from 1983to 1984. During that time seven roots showed changes in anatomicalstructure of the first type and two more were brought closer to thesurface and displayed the third type of change (Tables 1, 3; Figs. 3,5). The last period of significant change in the anatomy of rootswas in 1994–1998. Samples taken from the slope showed changesof root anatomy of the third type relating to that time and the sampletaken from the gully-like valley indicated changes of the first type(Tables 1, 2).
4.3. Plot 3
The samples collected from the third plot (i.e. the middle part of thegully) had become exposed between 1958 and 2001. In 1958 a root wasexposed on the bank of the gully about 0.4m above the bottomwith thefirst type of anatomical change. Two samples taken from the side of thegully had become exposed in 1970 and 1972 (the first type of change,Fig. 6), four in 1983 (the first type of change, Table 4), three more in1997 and a subsequent one in 2001 (Tables 1, 4; Figs. 3, 6). Three sam-ples, which were taken from steps composed primarily of roots at thebeginning of the gully-like valley, had become exposed between 1970,1994, and 1997 (Tables 1, 4; Fig. 6). Five of roots (during the period1983–1984) exhibit anatomical changes of the second type, followedby the changes of the third type. Five of roots which form steps on thebottom of gully revealed, after LW/EW changes, gradual return to thecommon growth structure (Table 4, Fig. 6).
Fig. 3. Column-graph showing the number of roots: 1— exposed, 2— changed due to the abrupt decrease of surface layer thickness and reduction of the distance of the root to the surfacewithin different sites during particular years.
46 D. Wrońska-Wałach / Catena 118 (2014) 41–54
4.4. Plot 4
At the fourth site soil had been removed from the roots sampled be-tween 1983 and 2001 (Fig. 3). The exposed root samples were locatedon the bank of a ravine-like valley, approximately 0.2 to 1 m abovethe bottom of the ravine. Wood anatomy changes in the roots were re-corded starting from 1983 and 1984. Nevertheless, the largest numberof anatomical changes (i.e. five roots) within tree roots occurred in1997 and 1998. The abrupt increase in the amount of LW cells in theroots was significant in 1997. Subsequently a decrease in the size ofEW cells was observed the following year, 1998. Only one root showed
anatomical changes of the second type in 1983 with subsequentchanges of the first type in 2001 (Table 5).
4.5. Rainfall-induced root exposures
A comparison of the year of soil cover removalwith available rainfalldata indicated significant differences between the study sites describedabove. Both monthly and maximum daily precipitation correlated withthe year of root exposure in different parts of the headwater area(Figs. 7, 8). Data collected in the upper part of the headwater areaappears to correlate with the high intensity of precipitation, which
Table 1State of art about root responses to the geomorphological processes.
Anatomical changes in roots Geomorphological activity Authors describing the changes connected with processes
Type 1 Abrupt increasing of the percentage of LWwith decreasing of thelumen area of EE wood tracheids and amount of EW withinconsecutive tree-ring, decreasing of the EW tracheid size withincreasing of the percentage of LW in the same tree-ring
Extreme events such as torrential flow,gully erosion or slope wash
Ballesteros-Cánovas et al. (2013); Buchwał (2008);Gärtner et al. (2001); Gärtner (2003, 2006, 2007)
Type 2 Abrupt changes (from the common root structure) of the treering width with significant increasing of the percentage of LW(to about 50–60% of tree ring) without, in the consecutive year,the changes of the lumen area of EW tracheids. Such anatomicalchanges were considered as a mark of the reduction of soil coverwithout exposure of a root.
Moderate M–F, slope wash or piping Bodoque et al. (2005); Bodoque et al. (2011);Corona et al. (2011); Gärtner (2003, 2006, 2007);Rubíales et al. (2008); Wrońska-Wałach et al. (2014)
Type 3 Gradual changes of the lumen area of EW with constantpercentage of LW, gradual decreasing of EW tracheids andincreasing of LW percentage
Continuous denudation Ballesteros-Cánovas et al. (2013); Bodoque et al. (2011);Corona et al. (2011); Pelfini and Santilli (2006); Saez et al. (2011)
47D. Wrońska-Wałach / Catena 118 (2014) 41–54
occurred in 1958, 1968, 1970 and 1972. On the other hand, years of rootexposure in the middle and lower parts of the headwater area corre-spond more to the rainy seasons of 1997 and 2001 (Fig. 8).
Linear regression analysis was performed between the number ofroots exhibiting anatomical changes and various precipitation data(Fig. 10). The root change–rainfall data relationship is evident whenroot changes are plotted against maximum daily precipitation fromthe Rabka station for the period from 1955 to 2007 (r = 0.63; r2 =0.40 — Fig. 10). A statistically significant relationship was obtained byplotting root anatomical change years versus maximum August precip-itation at the Rabka station (r = 0.50; r2 = 0.25). A statistically signifi-cant relationship was also found between changes in root anatomy andmaximum daily precipitation data from Turbacz station (r= 0.64; r2 =0.41) for the period 1956–1981 (Fig. 10). Furthermore, in some cases,total monthly precipitation coincided with root exposure. Peaks in Julyprecipitation correlate with root exposure in 1970 and 1997 (Fig. 8).In the case of 1997, sudden exposure can be identified in the majority(63%) of the exposed roots in the lower part of the headwater area(Fig. 3). Nevertheless, no correlation was found between the numberof roots and the total amount of May, June, July and Septembermonthlyprecipitation.
5. Discussion
5.1. Morphologically effective extreme events determined from root EWandLW changes
The use of the anatomical responses of roots in assessing the dates ofabrupt exposure has some history in geomorphology (Table 1). Various
Fig. 4. Graph showing annual values of the mean lumen area size of earlywood, within roots ta1983–1984 years of exposure.
anatomical changes are currently applied in order to analyse thosechanges from the anatomical structure of both EW and LW cells. In-creased ring width, increased percentage of LW, as well as decreasedEW cell size, are considered signatures of the moment of root exposure(Ballesteros-Cánovas et al., 2013). This analysis has proved that overallanatomical changes within spruce roots after exposure and abruptchanges in the percentage of LW/EW (without the significant changesin EE tracheids) before the final exposure (Fig. 2C) can be crucial inthe recognition of morphologically active periods occurring in headwa-ter areas. Gärtner (2003, 2006) described the nature of significantchanges in conifer root structure brought about by a change in the dis-tance of the root from the surface due to the erosion of the surfacelayer. This lag in the signal has been recently reported by Bodoqueet al. (2011) and Corona et al. (2011) and could also be the case forthe analysis of spruce roots growing in the study area. In some samplesan abrupt change of LWcells can be discerned in the study plots even 11or 18 years before exposure occurred (Fig. 2-C). Increases in LW beforeexposurewere observed in about 32% of roots. Such a time lag observedin a number of roots gives an additional opportunity to carry out amorecomplete analysis of the geomorphologically effective periods withinthe headwater areas (Table 2, Fig. 3).
This analysis proved that the majority of roots in headwater areaswere exposed in two stages. In a first stage, part of the soil cover was re-moved from some roots during a rainfall event and a significant changeof the percentage of EW/LW occurred (Figs. 2, 3). In a second stage thesame roots were exposed and distinct changes occurred within the EW(Figs. 2, 3). The standard root structure is typical of roots growing15–20 cm below the surface (Gärtner, 2003). An abrupt increase inthe percentage of LW can occur within roots whose position in the soil
ken from a rill in the centre of a torrential fan. Ellipse indicates the group representing the
changes from about 20–15 cm to about 10–5 cm below the surface (on-going experiment). Therefore an analysis based only on EW changescould cause the amount of material removed during a particular periodto be overestimated in some cases. Subsequently, such a situation couldlead to a misunderstanding of the morphologically effective rainfallevents.
5.2. Type of precipitation versus geomorphic effectiveness
Starkel (1979, 1996, 2002), in a wide-ranging discussion of the typesof geomorphic processes associated with heavy daily rainfall events,emphasised that such heavy rainfall creates an intensive surface run-offand slope wash-out, as well as gully erosion and shallow torrentialflows on steeper gradients. In addition, according to Gomi et al. (2002),local, short-lasting downpour is often observed in headwater systems.Moreover, headwater areas respond rapidly to intense rainfall becauseof their relatively small retention capacity and shorter flow paths. Thepossibility of analysing the complexity of headwater systems in response
Table 3Characteristic of exposed roots with the type of exposition — plot 2.
Id of root Localization of root LW changes EW changes Type of anatomical changesa
O_1 Gully— plot 2 1984 1985 1O_2 Gully— plot 2 1979 1991 2/3O_3 Gully— plot 2 1943 1944 1O_4 Gully— plot 2 1997 1998 1O_5 Gully— plot 2 1973 1973 1O_8 Rock veneer 1984 1984 1O_12 Rock veneer 1968 1978 1 → 1O_13 Rock veneer 1953 1953 1O_14 Rock veneer 1973 1973 1O_15 Rock veneer 1969 1971 2 → 1O_16 Rock veneer 1971 1971 1O_17 Rock veneer 1983 1997O_18 Rock veneer 1983 1984 1O_20 Rock veneer 1978 1979 1O_21 Rock veneer 1983 1984 1O_22 Rock veneer 1978 1989 2 → 3O_23 Rock veneer 1983 1984 1O_24 Rock veneer 1969 1978 3O_26 Rock veneer 1983 1984 1O_28 Slope 1958, 1968 1997 2 → 3 → 1
to heavy rainfall events emerged from dendrogeomorphological analysisof both EW and LW changes within roots taken from the different land-forms located in the upper parts of headwater areas. Thanks to the LWapproach it was concluded that certain parts of headwaters displayeda greater resistance to identical rainfall events than others. For example,with a maximum daily precipitation of 121.6 in 1970, 84.4 mm in 1971,and 120.4mm in 1972, the rock veneer described above (Plot 2) had be-comeonly slightly transformed (Table 3). Only three roots from the out-ermost part of the root system had been brought closer to the surfaceand four had become exposed (Figs. 3, 5, Table 3). The gully-like valleydownward from the rock veneer had become about 0.2 m wider anddeeper. Two of the roots analysed had been growing one above theother (Fig. 3) and abrupt change of LW was observed within the rootgrowing below in 1970. Thus the dominant processes in this part ofthe headwater area can be identified as slope wash and, due to the ear-lier exposure of roots growing belowother roots (for example O_22wasbelow O_23 — Fig. 3, Tables 1, 3), as piping. At the same time,neighbouring slopes had become dissected by torrential flows, which
Comments
–
Abrupt change of LW followed by gradual changes of EE tracheidsThe earliest registered exposure–
–
–
After exposure, gradual return to common growth structure, exposure in 1978
Changes indicate abrupt exposure–
Changes indicate abrupt exposureAfter abrupt LW change, gradual return to common growth structure, exposure in 1997–
After exposure, gradual return to common growth structure (Fig. 5)–
From 1983 gradual decrease of EE tracheids–
Gradual increase of LW until 1978, from 1974 gradual decrease of EE tracheids (Fig. 5)–
After abrupt LW change in 1958 and 1968 gradual return to common growthstructure, exposure in 1997Gradual changes of LW and EW until 1978–
Gradual changes of LW and EW until 1983Gradual changes of LW until 1997 when exposureAbrupt change of LW, followed by gradual decrease of EE tracheidsAbrupt change of LW, followed by gradual decrease of EE tracheids
Fig. 5. Geomorphologial outline of the second site (rock veneer with small gully in the lower part). Graphs showing annual variation of the mean lumen area size of earlywood (black line) of particular roots taken from the gully (O_3, O_5) and rockveneer (O_14, O_15, O_16, O_20, O_22, O_23, O_24). Black arrows indicate the first tree rings after the exposure (Wrońska-Wałach, 2009 — modified).
Fig. 6.Geomorphological outline of the third site (examples of roots exposed in a gully-like valley). Graphs showing annual variation of themean lumen area size of earlywood (black line).Black arrows indicate the first tree rings after the exposure.
Table 4Characteristic of exposed roots with the type of exposition — plot 3.
Id of root Localization of root LW changes EW changes Type of anatomical changesa Comments
O_58 Gully — plot 3 1983 1984 1 Decreasing of EE tracheids following LW changesO_59 Gully — plot 3 1983, 1997 1998 2 → 1 After LW change, gradual return to common growth structureO_60 Gully — plot 3 1983 1997 2 → 1 After LW change, gradual return to common growth structureO_61 Gully — plot 3 1958 1959 1 Root from the bottom of gullyO_62 Gully — plot 3 1984 2001 2 → 1 After LW change, gradual return to common growth structure, exposure in 2001O_63 Gully — plot 3 1984, 1989 1989 2 → 3 Gradual changes of LW and EW, exposure about 1989O_64 Gully — plot 3 1971 1971 1 Root from the bank of gullyO_65 Gully — plot 3 1973 1973 1 Root from the bank of gullyO_66 Gully — plot 3 1984, 1989 1995 2 → 3 After LW change, gradual return to common growth structureO_67 Gully — plot 3 1989 1997 1 → 1 After exposure in 1989, gradual return to common growth structure (Fig. 6),
Table 5Characteristic of exposed roots with the type of exposition — plot 4.
Id of root Localization of root LW changes EW changes Type of anatomical changesa Comments
O_50 Ravine 1983 1984 1 –
O_51 Ravine 1997 1997 1 –
O_52 Ravine 1997 1997 1 –
O_53 Ravine 1983 2001 2 → 1 After LW change, gradual return to common growth structureO_54 Ravine 1983 1984 1 –
O_55 Ravine 1997 1998 1 –
O_56 Ravine 1997 1998 1 –
O_57 Ravine 1997 1998 1 –
a For explanation see Table 1.
51D. Wrońska-Wałach / Catena 118 (2014) 41–54
resulted in the formation of torrential channels and torrential fans.Changes were recorded in EW cells within seven of eight of the rootsanalysed. The morphometric characteristics of the channels are about120 m in length, 1–2 m in depth, and on average 2 m in width. Thisleads to the conclusion, which is in agreement with the mattersdiscussed by Starkel (2012). The type and thickness of substrate areimportant agents thus different parts of the headwater areas can exhibitdifferent degrees of resistance to transformations during the samerainfall events.
Continuous rainfall, such as that which occurred in the Polishflysch-type Carpathians in 1997 and 2001, contributed to the trans-formation of the lower part of the headwater study area. As pointedout by Sidle et al. (2000), during such events there is a linear con-tribution from the upper parts of the headwater areas (zero-orderbasins) to the lower parts of the headwater areas (first-order chan-nels). Once a threshold of antecedent moisture in a zero-orderbasin is reached, subsurface flow begins and this yields stormrunoff (Sidle et al., 2000). In this way, the fluvial system expandsinto the temporary channels available in the headwater area.Dendrogeomorphological analysis conducted in the Gorce Mts. con-firmed the theoretical model of the headwater system. Roots exposedduring continuous rainfall in 1997 and 2001 were mainly found in thelower part of the headwater system (Fig. 3). Moreover, the number ofroots exposed in 1997 and 2001 increased downstream (comparewith Figs. 1, 3 — Plot 3, 4). This could act as confirmation that duringsuch events, the upper part of the headwater systembehaves as a reten-tion basin, which supplies water to its lower parts. Therefore, thesetypes of rainfall events are mainly morphologically effective in thelower parts of the headwater areas (Fig. 1).
The correlation between changes in wood anatomy in the root andrainfall data from different periods and types of rainfall confirmed this
Fig. 7. Comparison of maximum 24-h precipitation with
variation (Figs. 7, 8). The characteristics of the headwater system de-scribed above explain the difficulties in understanding the relationshipsbetween rainfall and the number of roots exhibiting anatomical changesdue to exposure. Various factors lead from the rainfall event to theactivation of the geomorphological processes within different parts ofthe headwater system (Fig. 10). It is possible that a lower correlationbetween precipitation data and root changes for the period from 1955to2007 for the Rabkameteorological station could be caused by the dis-tance of the meteorological station from the study area. It is importantto note that the correlation coefficient is strongly influenced by thelarge number of roots exhibiting changes in 1983 to 1984, with higherprecipitation being recorded at the Rabka station in 1983 (Figs. 7, 10).Malik (2008) and Starkel (2012) identified the methodological prob-lems associated with the correlation between rainfall data and extremeerosion events due to the highly localised nature of storm cells aswell asthe distance to particular meteorological stations. This could be true ofthe headwater areas studied. Nonetheless, further findings showed astatistically significant correlation (p b 0.05) between changes in thewood anatomy of the roots and maximum daily precipitation at boththe Rabka and Turbacz stations from 1956 to 1981 (Fig. 10). Some ofthe highest daily precipitation values and largest heavy rainfall eventswere recorded in the Carpathian Mountains during this time periodand are believed to have been associated with very strong storm cells,i.e. up to 100 km in diameter (Niedźwiedź, 1971). Significant amountsof daily precipitation were recorded at both meteorological stationsand correlated well with changes in the wood anatomy of the roots(Fig. 10). It is worth to evoke, that the study area under considerationwas located less than 9 km fromRabka and less than 1 km from Turbaczmeteorological stations, therefore it could demonstrate a reliable con-nection between rainfall and different geomorphic processes withinthe headwater area.
% of exposed or brought closer to the surface roots.
Fig. 8. Comparison of the amount of precipitation in July (A) and August (B) with % of exposed or brought closer to the surface roots (Wrońska-Wałach, 2009 — modified).
52 D. Wrońska-Wałach / Catena 118 (2014) 41–54
5.3. Dating of events
Changes in rootswere comparedwithprecipitation data on anannu-al basis. Hence, it is very important to identify the year when soil coverwas removed and the root became exposed to external factors. A lack ofring width measurements may contribute to erroneous estimations ofthe time when the headwater area became transformed by extremegeomorphological processes. In such a situation, a local reference chro-nology and cross-dating of roots (chronological curve) should be testedin detail.
Anatomical structure in roots found in a subsurface differs rathersubstantially from that observed in roots exposed to environmental fac-tors. The highest correlation (Gl = 81, p b 0.05) was observed betweenthe growth curves obtained from unexposed parts of roots. The mostdistinct changes in ring widths occur in the case of conifer roots,which have a reduced distance to the surface due to the erosional pro-cesses. Roots react to the removal of soil cover by producing a thicklayer of LW cells, which markedly increases annual growth (Bodoqueet al., 2005; Corona et al., 2011; Gärtner, 2003; Rubíales et al., 2008).This change takes place rather uniformly across the entire cross-section of a root. The average correlation coefficient between roots ofthis kind in the study area was Gl = 63 (p b 0.05). On the other hand,ring widthmeasurements on an exposed root are muchmore problem-atic. The average correlation coefficient between roots of this kind wasGl = 51 (p b 0.05). This led to the conclusion that the exposed part ofa root requires more precise ringwidthmeasurements with applicationof both visual cross-dating and serial-sectioning. When a coniferroot becomes exposed, not only do EW cells change but the entire
anatomical structure changes as well. Annual growth rings may consti-tute even less than 50% of the entire cross section after root exposurecommonly inducing the formation of wedging rings, especially withinroots with erosional scars. In order to produce a reference chronology,it is necessary to analyse the entire root cross section with a minimumof four radii and separately perform cross-dating of each root analysed(Wrońska-Wałach et al., 2012, 2014). The presence of wedging ringsin roots, which account for less than 50% of the entire cross section, aswell as the presence of erosional scars and traumatic resin ducts(TRD), may be an indication of missing rings in roots experiencingsubstantial environmental pressure.
Cross-dating of roots with stem reference chronology could increasethe accuracy of dating. Unfortunately, in a previous analysis low correla-tion was obtained between root and stem chronology (Pelfini andSantilli, 2006; Wrońska-Wałach et al., 2012). Therefore, other methodsshould support the cross-dating of roots. One method that could behelpful in some situations in increasing the accuracy of the dating ofroot exposure could be a detailed analysis of LW and EW changes andtheir relationship with heavy rainfall. Two types of rainfall eventswere distinguished. Each type is characterised by different morpholog-ical effectiveness in particular parts of the headwater area. Changes inthe wood anatomy of EW and LW cells in conifer roots taken from theupper part of the headwater area primarily correlate with maximumdaily precipitation in the years 1958, 1968, 1970, 1971, 1972, 1983and 1984 (Fig. 3). Changes in the structure of LW cells in 1972 werefollowed by changes in EW cells in 1973 (Fig. 2-B, D). A similar situationwas observed for the years 1983 and 1984. One possible explanation forEW cell size changes being delayed to the following year is that the root
Fig. 9. Examples of anatomical changes in LW and EW caused by the exposure of roots:(A) (O-72)— exposure in 1972 at the end of the vegetation season or during the dormantseason; therefore, early EW cells are smaller the following year (1983— the root becamescarred, which can be inferred from the presence of traumatic resin ducts (TRD)),(B) x(O-76) — the root was brought closer to the surface in 1971, exposed in 1972, andscarred in 1972 (the scar dates back to 1972 and is located on the opposite side of theroot) (see Fig. 2-D).
53D. Wrońska-Wałach / Catena 118 (2014) 41–54
may have been exposed at the end of the growing season after EW cellshad already been fully formed. A similar process was discussed byMalik(2008) in European beech root samples. This is the result of well-established wood formation and growth periods that normally occurbetween May and November in temperate climatic zones (Zielski andKrąpiec, 2004).
High daily rainfall totals correlate with root exposure in 1958, 1968,1970, 1971, 1972, 1978, and 1979 (Fig. 7). Missing rings and wedgingrings in such a situationwould be able to cause themisdating of root ex-posure, especially during the period 1970–1972. But rainfall occurredduring different months in individual years. In 1958, 1971, and 1978 a
Fig. 10. The relationship between number of root exhibiting anatomical changes and 24-hprecipitation data from Rabka and Turbacz meteorological stations.
number of heavy rainfall events (i.e. N70 mm) occurred at the end ofMay and in June featuring the following amounts of rainfall: 113.3mm, 84.4 mm, and 72.8 mm, respectively (Fig. 7). Structural changesin LW cells were determined to have taken place during the sameyears as downpours were recorded. On the other hand, EW cells de-creased in size in the years following the aforementioned downpours(Fig. 9B). In the remaining years, heavy rainfall events occurred duringthe secondpart of July or in August. Changes inwood anatomy in coniferroots were observed in both EW and LW cells in the following year(Fig. 9A).
6. Conclusions
In this study dendrogeomorphological analysis revealed a significantdivergence in the year of exposure between roots taken from the upperpart of the headwaters of interest and those taken from the middle andlower parts. Analysis of the structural changes in 59 root samples indi-cated their exposure related to specific types of geomorphic processes.
Hence, the upper and lower parts of the headwater area have beenshown to experience non-synchronous development. The upper parthas become transformed during extreme rainfall events. The responseof the lower part of the headwater area is more predictable than itsupper part. Dendrogeomorphological analysis revealed that the lowerpart mostly undergoes physical transformations during summer rainyseasons. The transformations include the deepening of channels, lateralundercutting, as well as landslide events on channel sides.
Synchronous hydro-geomorphic activity of the headwater systemcould be observed during seasons which experience both continuousrainfall and heavy rainfall events. The analysis presented herein provedthe relationship described above. Nevertheless, it would be interestingto find the connections between the headwater system and the fluvialsystem located downstream. For this reason, further research is neces-sary in order to create a working model that would accurately describethe functional nature of the whole mid-mountain systems.
The relationship between rainfall data and the number of EW andLW changes in roots is a promising avenue for future research. It canbe crucial for the establishment of rainfall thresholds for different geo-morphological processes drawing in the headwater area.
The analysis of both EW and LW changes within roots increases theaccuracy of dating and the estimation of the geomorphic effectiveness ofvarious geomorphological processes.
Acknowledgements
This project was supported by the State Committee for Scientific Re-search (KBN Project No. 086/P04/2003 and No. 2824/B/P01/2009/36). Iwould also like to thank Anna Michno and Elżbieta Gorczyca and PiotrWałach for their help with fieldwork.
References
Alestalo, J., 1971. Dendrochronological interpretation of geomorphic processes. Fennia105, 1–140.
Ballesteros-Cánovas, J.A., Bodoque, J.M., Lucía, A., Martín-Duque, J.F., Díez-Herrero, A.,Ruiz-Villanueva, V., Rubiales, J.M., Genova, M., 2013. Dendrogeomorphology inbadlands: methods, case studies and prospects. Catena 106, 113–122.
Benda, L., 1990. The influence of debris flows on channels and valley floors of the OregonCoast Range, U.S.A. Earth Surf. Process. Landf. 15, 457–466.
Bodoque, J.M., Díez-Herrero, A., Martín-Duque, J.F., Rubiales, J.M., Godfrey, A., Pedraza, J.,Carrasco, R.M., Sanz, M.A., 2005. Sheet erosion rates determined by usingdendrogeomorphological analysis of exposed tree roots: two examples from CentralSpain. Catena 64, 81–102.
Bodoque, J.M., Lucía, A., Ballesteros, J.A., Martín-Duque, J.F., Rubiales, J.M., Genova, M.,2011. Measuring medium-term sheet erosion in gullies from trees: a case studyusing dendrogeomorphological analysis of exposed pine roots in central Iberia.Geomorphology 134 (3–4), 417–425.
Bollschweiler, M., Stoffel, M., Monbaron, M., 2007. Reconstructing spatio-temporal pat-terns of debris flow activity using dendrogeomorphologicalmethods. Geomorphology87, 337–351.
Buchwał, A., 2008. Dendrogeomorphological records of trail erosion. TRACE 7, 166–170.
Buchwał, A., Rachlewicz, G., Fonti, P., Cherubini, P., Gärtner, H., 2013. Temperaturemodulates intra-plant growth of Salix polaris from a high Arctic site (Svalbard).Polar Biol. 36, 1305–1318.
Carrara, P.E., Carroll, T.R., 1979. The determination of erosion rates from exposed treeroots in the Piceance basin Colorado. Earth Surf. Process. Landf. 4, 307–317.
Chwistek, K., 2001. Dynamics of tree stands in the Gorce National Park (Southern Poland)during the period 1992–1997. Nat. Conserv. 58, 17–32.
Corona, C., Lopez, J., Rovéra, G., Stoffel, M., Astrade, L., Berger, F., 2011. High resolution,quantitative reconstruction of erosion rates based on anatomical changes in exposedroots (Draix, Alpes de Haute-Provence) — critical review of existing approaches andindependent quality control of results. Geomorphology 125, 433–444.
Crozier, M.J., 1986. Landslides: Causes, Consequences and Environment. Croom Helm,London.
Denne, M.P., 1988. Definition of Latewood according to Mork (1928). IAWA Bulletin 10(1), 59–62.
Dietrich, W.E., Dunne, T., 1978. Sediment budget for small catchment in mountainousterrain. Z. Geomorphol. 29 (Suppl.Bd), 191–206.
Ellen, S.D., Wieczorek, G.F., 1988. Landslides, floods and marine effects of the storm ofJanuary 3–5 1982, in the San Francisco Bay Region California. US Geol. Surv. Prof.Pap. 1434, 1–310.
Froehlich, W., Starkel, L., 1995. The response of slope and channel systems to varioustypes of extreme rainfalls (temperate zone–humid tropics comparison). Geomor-phology 11 (4), 337–346.
Gärtner, H., 2003. Holzanatomische Analyse diagnostischer Merkmale einerFreilegungsreaktion in Jahrringen von Koniferenwurzeln zur Rekonstruktiongeomorphologischer Prozesse. (Dissertationes) Botanicae 378, 1–118.
Gärtner, H., 2006. The applicability of roots in dendrogeomorphology. TRACE 1, 120–124.Gärtner, H., 2007. Tree roots — methodological review and new development in dating
and quantifying erosive processes. Geomorphology 86 (3–4), 243–251.Gärtner, H., Schweingruber, F.H., Dikau, R., 2001. Determination of erosion rates by ana-
lyzing structural changes in the growth pattern of exposed roots. Dendrochronologia19 (1), 81–91.
Gil, E., Starkel, L., 1979. Long-term extreme rainfalls and their role in the modelling offlysch slopes. Stud. Geomorph. Carpatho-Balc. 13, 207–220.
Gomi, T., Sidle, R.C., Richardson, J.S., 2002. Understanding processes and downstreamlinkages of headwater systems. Bioscience 52 (10), 905–916.
Hess, M., 1965. Piętra klimatyczne w Polskich Karpatach Zachodnich. Zesz. Nauk. UJ Pr.Geogr. 11, 1–258.
Hitz, O.M., Gärtner, H., Heinrich, I., Monbaron, M., 2008. Application of ash (Fraxinusexelsior L.) roots to determine erosion rates inmountain torrents. Catena 72, 248–258.
Holmes, R.L., 1983. Computer-assisted quality control in tree ring dating and measure-ment. Tree-Ring Bull. 43, 69–77.
Huber, B., 1943. Uber die sicherheit jahrringchronologischer Datierung. Holz als Roh-undWerkstoff. 6, 263–268.
Jacobson, R.B., Miller, A.J., Smith, J.A., 1989. The role of catastrophic geomorphic events incentral Appalachian landscape evolution. Geomorphology 2 (1–3), 257–284.
Kelsey, H.M., 1980. A sediment budget and an analysis of geomorphic process in the VanDuzen River Basin, North Coastal California, 1941–1975. Geol. Soc. Am. Bull. 91 (4),1119–1216.
Klimaszewski, M., 1972. Geomorfologia Polski Polska Południowa-góry i wyżyny. PWN,Warszawa.
Kolishchuk, V., 1990. Dendroclimatological Study of Prostrate Woody Plant. In: Cook, E.R.,Kairiukstis, L.A. (Eds.), Methods of dendro-chronology: Applications in the environ-mental sciences. Kluwer Academic Publ., Dordrecht, pp. 51–55.
Kotarba, A., 1998. Morfogenetyczna rola opadów deszczowych w modelowaniu rzeźbyTatr podczas letniej powodzi w roku 1997. Dokumentacja Geogr. IGiPZ PAN. 12, 9–23.
LaMarche, V.C., 1968. Rates of slope degradation as determined from botanical evidenceWhite Mountains California. US Geol. Surv. Prof. Pap. 352, 341–377.
Loch, J., Chwistek, K., Wężyk, P., Małek, S., Pająk, M., 2001. Natural regeneration versustree planting in the subalpine spruce forest Plagiothecio-piceetum Tatricum of theGorce National Park (Southern Poland). Nat. Conserv. 58, 5–15.
Malik, I., 2008. Dating of small gully formation and establishing erosion rates in old gulliesunder forest by means of anatomical changes in exposed tree roots (SouthernPoland). Geomorphology 93 (3–4), 421–436.
Malik, I., Matyja, M., 2008. Bank erosion history of a mountain stream determined bymeans of anatomical changes in exposed tree roots over the last 100 years (BíláOpava River — Czech Republic). Geomorphology 98 (1–2), 126–142.
Montgomery, D.R., Dietrich, W.E., 1988. Where do channels begin? Nature 336, 232–234.Nemčok, A., 1982. Zosuvy v Slovenskych Karpatoch (slovac language, summary of
chapters in english). Veda, Bratislava.Niedźwiedź, T., 1971. Opady atmosferyczne w Polsce południowej w czasie powodzi
lipcowej 1970 r. Sprawozdania z Posiedzeń Komisji Naukowej Oddziału PAN wKrakowie, 25, 1, pp. 189–191.
Pelfini, M., Santilli, M., 2006. Dendrogeomorphological analyses on exposed roots alongtwo mountain hiking trails in the central Italian Alps. Geogr. Ann. 88 A (3), 223–236.
Pelfini, M., Santilli, M., 2008. Frequency of debris flows and their relation with precipita-tion: a case study in the Central Alps Italy. Geomorphology 101, 721–730.
Pérez-Rodríques, R., Marques, M.J., Bienes, R., 2007. Use of dendrochronological methodin Pinus halepensis to estimate the soil erosion in the South East of Madrid (Spain).Sci. Total Environ. 378, 156–160.
Rubíales, J.M., Bodoque, J.M., Ballesteros, J.A., Díez-Herrero, A., 2008. Response of Pinussylvestris roots to sheet-erosion exposure: an anatomical approach. Nat. HazardsEarth Syst. Sci. 8, 223–231.
Saez, J.S., Corona, C., Stoffel, M., Rovéra, G., Astrade, L., Bérgér, F., 2011. Mapping of erosionrates in marly badlands based on a coupling of anatomical changes in exposed rootswith slope maps derived from LIDAR data. Earth Surf. Process. Landf. 36 (9),1162–1171.
Schweingruber, F.H., 1988. Tree rings - basics and applications of dendrochronology.Dordrecht, Netherlands.
Schweingruber, F.H., 1990. Microskopische Holzanatomie. Anatomie microscopique dubois. Microscopic Wood AnatomySwiss Federal Institute for Forest, Snow andLandscape Research.
Schweingruber, F.H., 1996. Tree Ring and Environment Dendroecology. Swiss FederalInstitute for Forest Snow and Landscape Research, WSL/FNP, Haupt, Birmensdorf.
Sidle, R.C., Tsuboyama, Y., Noguchi, S., Hosoda, I., Fujieda, M., Shimizu, T., 2000. Stormflowgeneration in steep forested headwaters: a linked hydrogeomorphic paradigm.Hydrol. Process. 14, 369–385.
Šilhán, K., Pánek, T., 2010. Dynamics of debris flows in the Moravskoslezské Beskydy Mts.(Czech republic). Stud. Geomorph. Carpatho-Balc. 44, 49–60.
Starkel, L., 1979. On some questions of the contemporary modelling of slopes and valleybottoms in the flysch Carpathians. Stud. Geomorph. Carpatho-Balc. 13, 191–207.
Starkel, L., 1996. Geomorphic role of extreme rainfalls in the Polish Carpathians. Stud.Geomorph. Carpatho-Balc. 30, 21–38.
Starkel, L., 2002. Change in the frequency of extreme events as the indicator of climaticchange in the Holocene (in fluvial systems). Quat. Int. 91, 25–32.
Starkel, L., 2006. Geomorphic hazards in the polish flysch Carpathians. Stud. Geomorph.Carpatho-Balc. 40, 7–19.
Starkel, L., 2012. Searching for regularities of slope modelling by extreme events (diversi-ty of rainfall intensity–duration and physical properties of the substrate). LandformAnal. 21, 27–34.
Stoffel, M., 2006. A review of studies dealing with tree rings and rockfall activity: the roleof dendrogeomorphology in natural hazard research. Nat. Hazards 39, 51–70.
Wrońska-Wałach, D., 2009. Dendrogeomorphological analysis of a headwater area in theGorce Mountains. Stud. Geomorph. Carpatho-Balc. 63, 97–114.
Wrońska-Wałach, D., Gorczyca, E., Buchwał, A., Korpak, J., Sobucki, M., Wałdykowski, P.,2012. Problemy metodyczne analizy dendrochronologicznej procesów erozyjnychw zlewniach górskich. Studia i Materiały Centrum Edukacji Przyrodniczo-Leśnej 1(30), 195–202.
Wrońska-Wałach, D., Gorczyca, E., Sobucki, M., Buchwał, A., Korpak, J., Wałdykowski, P.,2014. Quantitative analysis of secondary growth in spruce roots and its applicationfor precise roots dating. Dendrochronologia.
Zielonka, T., Holeksa, J., Ciapała, S., 2008. A reconstruction of flood events using scarredtrees in the Tatra Mountains Poland. Dendrochronologia 26, 173–183.
Zielski, A., Krąpiec, M., 2004. Dendrochronologia. PWN, Warszawa.Ziętara, T., 1968. Rola gwałtownych ulew i powodzi wmodelowaniu rzeźby Beskidów. Pr.
