@article{BartholdStallardElsenbeer2008, author = {Barthold, Frauke Katrin and Stallard, Robert F. and Elsenbeer, Helmut}, title = {Soil nutrient-landscape relationships in a lowland tropical rainforest in Panama}, issn = {0378-1127}, doi = {10.1016/j.foreco.2007.09.089}, pages = {1135-1148}, year = {2008}, abstract = {Soils play a crucial role in biogeochemical cycles as spatially distributed sources and sinks of nutrients. Any spatial patterns depend on soil forming processes, our understanding of which is still limited, especially in regards to tropical rainforests. The objective of our study was to investigate the effects of landscape properties, with an emphasis on the geometry of the land surface, on the spatial heterogeneity of soil chemical properties, and to test the suitability of soil-landscape modeling as an appropriate technique to predict the spatial variability of exchangeable K and Mg in a humid tropical forest in Panama. We used a design-based, stratified sampling scheme to collect soil samples at 108 sites on Barro Colorado Island, Panama. Stratifying variables are lithology, vegetation and topography. Topographic variables were generated from high-resolution digital elevation models with a grid size of 5 m. We took samples from five depths down to I m, and analyzed for total and exchangeable K and Mg. We used simple explorative data analysis techniques to elucidate the importance of lithology for soil total and exchangeable K and Mg. Classification and Regression Trees (CART) were adopted to investigate importance of topography, lithology and vegetation for the spatial distribution of exchangeable K and Mg and with the intention to develop models that regionalize the point observations using digital terrain data as explanatory variables. Our results suggest that topography and vegetation do not control the spatial distribution of the selected soil chemical properties at a landscape scale and lithology is important to some degree. Exchangeable K is distributed equally across the study area indicating that other than landscape processes, e.g. biogeochemical processes, are responsible for its spatial distribution. Lithology contributes to the spatial variation of exchangeable Mg but controlling variables could not be detected. The spatial variation of soil total K and Mg is mainly influenced by lithology.}, language = {en} } @phdthesis{CameronSobierajElsenbeer2004, author = {Cameron, G. and Sobieraj, J. A. and Elsenbeer, Helmut}, title = {Scale dependency in spatial patterns of saturated hydraulic conductivity}, issn = {0341-8162}, year = {2004}, abstract = {This study investigates spatial patterns of Ks and tests the hypothesis of whether structural variance emerges from noise with increasing sampling precision. We analyzed point measurements of Ks along independent transects at sampling intervals of 25, 10, 1 and 0.25 m. The field area is a tropical rainforest catena (i.e. toposequence) characterized by systematic downslope changes in soil properties including color (red to yellow), mineralogy (kaolinite- illite to kaolinite) and texture (sandy clay to sand). Independent tramsects spanning the entire catena at lag intervals of 25 and 10 in reveal little to no spatial patterns in Ks; i.e. scatter plots are noisy and lack apparent spatial trends, and semivariograms suggest little to no autocorrelation in Ks. As sampling precision is increased (h = 1 and 0.25 m), spatial patterns emerge in Ks for the downslope areas, in which distinctive hydraulic boundaries in Ks correlate with relatively small-scale, topography-controlled soils with coarse textures (greater than or equal to 80\% sand). For these areas, semivariograms of Ks and those of \%sand and \%clay exhibit similar spatial structure characterized by small nugget variances and large ranges, and nugget variance is reduced as sampling precision increases from 1 to 0.25 m. In the upslope, clay-rich locations along this toposequence, Ks exhibits few spatial patterns, irrespective of sampling scale. For these locations, scatter plots are noisy without apparent spatial trends, and semivariograms show almost complete nugget variance, suggesting little to no correlation in this hydraulic parameter at any scale. This study suggests that in the absence of coarse textures (greater than or equal to 80\% sand), there is little predictability in Ks, even at sampling intervals of 0.25 m. We believe this lack of spatial structure is due to a predominance of small-scale processes such as biological activity that largely control Ks in this forested setting. (C) 2003 Elsevier B.V. All rights reserved}, language = {en} } @misc{ChavesNeillGermeretal.2009, author = {Chaves, Joaqu{\´i}n E. and Neill, Christopher and Germer, Sonja and Neto, Sergio Gouveia and Krusche, Alex V. and Bonilla, Adriana Castellanos and Elsenbeer, Helmut}, title = {Nitrogen transformations in flowpaths leading from soils to streams in Amazon forest and pasture}, issn = {1432-9840}, doi = {10.1007/s10021-009-9270-4}, year = {2009}, language = {en} } @article{ChavesNeillGermeretal.2008, author = {Chaves, Joaqu{\´i}n E. and Neill, Christopher and Germer, Sonja and Neto, S{\´e}rgio Gouveia and Krusche, Alex V. and Elsenbeer, Helmut}, title = {Land management impacts on runoff sources in small amazon watersheds}, issn = {0885-6087}, doi = {10.1002/hyp.6803}, year = {2008}, language = {en} } @misc{ElsenbeerCasselCastro1992, author = {Elsenbeer, Helmut and Cassel, Keith and Castro, Jorge}, title = {Spatial analysis of soil hydraulic conductivity in a tropical rain forest catchment}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16979}, year = {1992}, abstract = {The topography of first-order catchments in a region of western Amazonia was found to exhibit distinctive, recurrent features: a steep, straight lower side slope, a flat or nearly flat terrace at an intermediate elevation between valley floor and interfluve, and an upper side slope connecting interfluve and intermediate terrace. A detailed survey of soil-saturated hydraulic conductivity (K sat)-depth relationships, involving 740 undisturbed soil cores, was conducted in a 0.75-ha first-order catchment. The sampling approach was stratified with respect to the above slope units. Exploratory data analysis suggested fourth-root transformation of batches from the 0-0.1 m depth interval, log transformation of batches from the subsequent 0.1 m depth increments, and the use of robust estimators of location and scale. The K sat of the steep lower side slope decreased from 46 to 0.1 mm/h over the overall sampling depth of 0.4 m. The corresponding decrease was from 46 to 0.1 mm/h on the intermediate terrace, from 335 to 0.01 mm/h on the upper side slope, and from 550 to 0.015 mm/h on the interfluve. A depthwise comparison of these slope units led to the formulation of several hypotheses concerning the link between K sat and topography.}, language = {en} } @misc{ElsenbeerCasselTinner1993, author = {Elsenbeer, Helmut and Cassel, Keith and Tinner, W.}, title = {A daily rainfall erosivity model for Western Amazonia}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16962}, year = {1993}, abstract = {Rainfall erosivities as defined by the R factor from the universal soil loss equation were determined for all events during a two-year period at the station La Cuenca in western Amazonia. Three methods based on a power relationship between rainfall amount and erosivity were then applied to estimate event and daily rainfall erosivities from the respective rainfall amounts. A test of the resulting regression equations against an independent data set proved all three methods equally adequate in predicting rainfall erosivity from daily rainfall amount. We recommend the Richardson model for testing in the Amazon Basin, and its use with the coefficient from La Cuenca in western Amazonia.}, language = {en} } @misc{ElsenbeerCasselZuniga1994, author = {Elsenbeer, Helmut and Cassel, Keith and Zu{\~n}iga, L.}, title = {Throughfall in the terra firme forest of Western Amazonia}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16955}, year = {1994}, abstract = {Throughfall measurements were made under primary terra firme rainforest in the Rio Pichis valley, in the Upper Amazon Basin of Peru. Based on 214 precipitation events over nearly 18 months, throughfall was estimated to be 83.1±8.8\% of gross precipitation. Regression analysis of all events revealed that gross precipitation is the only significant explanatory variable; the use of one-burst events does not significantly improve the regression relationship. Gross precipitation is, however, a poor predictor of throughfall for small rainfall events. The two forest structure parameters, canopy capacity, S, and free throughfall coefficient, p, were determined to be 1.3±0.2 mm and 0.32±0.18 mm. Rainfall intensity was found to influence these parameters. New methods which attempt to minimize the influence of meteorologic variables are used to estimate the potential values of these canopy parameters.}, language = {en} } @misc{ElsenbeerLackCassel1995, author = {Elsenbeer, Helmut and Lack, Andreas and Cassel, Keith}, title = {Chemical fingerprints of hydrological compartments and flow paths at La Cuenca, western Amazonia}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16937}, year = {1995}, abstract = {A forested first-order catchment in western Amazonia was monitored for 2 years to determine the chemical fingerprints of precipitation, throughfall, overland flow, pipe flow, soil water, groundwater, and streamflow. We used five tracers (hydrogen, calcium, magnesium, potassium, and silica) to distinguish "fast" flow paths mainly influenced by the biological subsystem from "slow" flow paths in the geochemical subsystem. The former comprise throughfall, overland flow, and pipe flow and are characterized by a high potassium/silica ratio; the latter are represented by soil water and groundwater, which have a low potassium/silica ratio. Soil water and groundwater differ with respect to calcium and magnesium. The groundwater-controlled streamflow chemistry is strongly modified by contributions from fast flow paths during precipitation events. The high potassium/silica ratio of these flow paths suggests that the storm flow response at La Cuenca is dominated by event water.}, language = {en} } @misc{ElsenbeerLorieriBonell1995, author = {Elsenbeer, Helmut and Lorieri, Daniel and Bonell, Mike}, title = {Mixing model approaches to estimate storm flow sources in an overland flow-dominated tropical rain forest catchment}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16948}, year = {1995}, abstract = {Previous hydrometric studies demonstrated the prevalence of overland flow as a hydrological pathway in the tropical rain forest catchment of South Creek, northeast Queensland. The purpose of this study was to consider this information in a mixing analysis with the aim of identifying sources of, and of estimating their contribution to, storm flow during two events in February 1993. K and acid-neutralizing capacity (ANC) were used as tracers because they provided the best separation of the potential sources, saturation overland flow, soil water from depths of 0.3, 0.6, and 1.2 m, and hillslope groundwater in a two-dimensional mixing plot. It was necessary to distinguish between saturation overland flow, generated at the soil surface and following unchanneled pathways, and overland flow in incised pathways. This latter type of overland flow was a mixture of saturation overland flow (event water) with high concentrations of K and a low ANC, soil water (preevent water) with low concentrations of K and a low ANC, and groundwater (preevent water) with low concentrations of K and a high ANC. The same sources explained the streamwater chemistry during the two events with strongly differing rainfall and antecedent moisture conditions. The contribution of saturation overland flow dominated the storm flow during the first, high-intensity, 178-mm event, while the contribution of soil water reached 50\% during peak flow of the second, low-intensity, 44-mm event 5 days later. This latter result is remarkably similar to soil water contributions to storm flow in mountainous forested catchments of the southeastern United States. In terms of event and preevent water the storm flow hydrograph of the high-intensity event is dominated by event water and that of the low-intensity event by preevent water. This study highlights the problems of applying mixing analyses to overland flow-dominated catchments and soil environments with a poorly developed vertical chemical zonation and emphasizes the need for independent hydrometric information for a complete characterization of watershed hydrology and chemistry.}, language = {en} } @article{GermerElsenbeerdeMoraes2006, author = {Germer, Sonja and Elsenbeer, Helmut and de Moraes, Jorge M.}, title = {Throughfall and temporal trends of rainfall redistribution in an open tropical rainforest, south-western Amazonia (Rond{\^o}nia, Brazil)}, issn = {1027-5606}, doi = {10.5194/hess-10-383-2006}, year = {2006}, language = {en} } @article{GermerNeillKruscheetal.2010, author = {Germer, Sonja and Neill, Christopher and Krusche, Alex V. and Elsenbeer, Helmut}, title = {Influence of land-use change on near-surface hydrological processes : undisturbed forest to pasture}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2009.11.022}, year = {2010}, abstract = {Soil compaction that follows the clearing of tropical forest for cattle pasture is associated with lower soil hydraulic conductivity and increased frequency and volume of overland flow. We investigated the frequency of perched water tables, overland flow and stormflow in an Amazon forest and in an adjacent 25-year-old pasture cleared from the same forest. We compared the results with the frequencies of these phenomena estimated from comparisons of rainfall intensity and soil hydraulic conductivity. The frequency of perched water tables based on rainfall intensity and soil hydraulic conductivity was expected to double in pasture compared with forest. This corresponded closely with an approximate doubling of the frequency of stormflow and overland flow in pasture. In contrast, the stormflow volume in pasture increased 17-fold. This disproportional increase of stormflow resulted from overland flow generation over large areas of pasture, while overland flow generation in the forest was spatially limited and was observed only very near the stream channel. In both catchments, stormflow was generated by saturation excess because of perched water tables and near-surface groundwater levels. Stormflow was occasionally generated in the forest by rapid return flow from macropores, while slow return flow from a continuous perched water table was more common in the pasture. These results suggest that deforestation for pasture alters fundamental mechanisms of stormflow generation and may increase runoff volumes over wide regions of Amazonia.}, language = {en} } @article{GermerNeillKruscheetal.2007, author = {Germer, Sonja and Neill, Christopher and Krusche, Alex V. and Neto, Sergio Gouveia and Elsenbeer, Helmut}, title = {Seasonal and within-event dynamics of rainfall and throughfall chemistry in an open tropical rainforest in Rond{\^o}nia, Brazil}, issn = {0168-2563}, doi = {10.1007/s10533-007-9152-9}, year = {2007}, abstract = {Prolonged dry periods, and increasingly the generation of smoke and dust in partially-deforested regions, can influence the chemistry of rainfall and throughfall in moist tropical forests. We investigated rainfall and throughfall chemistry in a palm-rich open tropical rainforest in the southwestern Brazilian Amazon state of Rondonia, where precipitation averages 2300 mm year(-1) with a marked seasonal pattern, and where the fragmentation of remaining forest is severe. Covering the transition from dry to wet season (TDWS) and the wet season (WS) of 2004-2005, we sampled 42 rainfall events on event basis as well as 35 events on a within-event basis, and measured concentrations of DOC, Na+, K+, Ca2+, Mg2+, NH4+ , Cl-, SO42- , NO3- and pH in rainfall and throughfall. We found strong evidence of both seasonal and within-event solute rainfall concentration dynamics. Seasonal volume-weighted mean (VWMS) concentrations in rainfall of DOC, K+, Ca2+, Mg2+, NH4+ , SO42- and NO3- were significantly higher in the TDWS than the WS, while VWMS concentrations in throughfall were significantly higher for all solutes except DOC. Patterns were generally similar within rain events, with solute concentrations declining sharply during the first few millimeters of rainfall. Rainfall and throughfall chemistry dynamics appeared to be strongly influenced by forest and pasture burning and a regional atmosphere rich in aerosols at the end of the dry season. These seasonal and within-event patterns of rainfall and throughfall chemistry were stronger than those recorded in central Amazonia, where the dry season is less pronounced and where regional deforestation is less severe. Fragmentation and fire in Rondonia now appear to be altering the patterns in which solutes are delivered to remaining moist tropical forests.}, language = {en} } @article{GermerNeillVetteretal.2009, author = {Germer, Sonja and Neill, Christopher and Vetter, Tobias and Chaves, Joaqu{\´i}n E. and Krusche, Alex V. and Elsenbeer, Helmut}, title = {Implications of long-term land-use change for the hydrology and solute budgets of small catchments in Amazonia}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2008.11.013}, year = {2009}, abstract = {The replacement of undisturbed tropical forest with cattle pasture has the potential to greatly modify the hydrology of small watersheds and the fluxes of solutes. We examined the fluxes of water, Cl-, NO3--N: SO42---S, NH4+-N, Na+, K+, Mg2+ and Ca2+ in different flow paths in similar to 1 ha catchments of undisturbed open tropical rainforest and a 20 year-old pasture established from forest in the southwestern Brazilian Amazon state of Rondonia. Storm flow discharge was 18\% of incident rainfall in pasture, but only 1\% in forest. Quickflow predominated over baseflow in both catchments and in both wet and dry seasons. In the pasture, groundwater and quickflow were important flow paths for the export of all solutes. In the forest, quickflow was important for NO3--N export, but all other solutes were exported primarily by groundwater outflow. Both catchments were sinks for SO42--S and Ca2+, and sources of Na+. The pasture catchment also lost K+ and Mg2+ because of higher overland flow frequency and volume and to cattle excrement. These results show that forest clearing dramatically influences small watershed hydrology by increasing quickflow and water export to streams. They also indicate that tropical forest watersheds are highly conservative for most solutes but that pastures continue to lose important cations even decades after deforestation and pasture establishment.}, language = {en} } @article{GodseyElsenbeerStallard2004, author = {Godsey, S. and Elsenbeer, Helmut and Stallard, R. F.}, title = {Overland flow generation in two lithologically distinct rainforest catchments}, issn = {0022-1694}, year = {2004}, abstract = {Streams on uniformly rainforest-covered, but lithologically very diverse Barro Colorado Island in central Panamd show remarkable differences in their runoff response to rainfall. This lithological diversity is reflected in equally diverse soilscapes, and our objective was to test the hypothesis that contrasting runoff responses derive from soilscape features that control the generation of overland flow. We determined the soil saturated hydraulic conductivity (K-s) of two neighboring, but hydrologically contrasting catchments (Lutz Creek with a flashy and Conrad Trail with a delayed response to rainfall), and quantified the spatial and temporal frequency of overland flow occurrence. The median K-s values at a depth of 12.5 cm are large enough to rule out Hortonian overland flow, but a marked decrease in K-s in Lutz Creek catchment at 30 cm suggests the formation of a perched water table and the generation saturation overland flow; the decrease in K-s in the Conrad Trail catchment is more gradual, and a perched water table is expected to form only at depths below 50 cm. In Lutz Creek, overland flow was generated frequently in time and space and regardless of topographic position, including near the interfluve, with very low thresholds of storm magnitude, duration, intensity and antecedent wetness, whereas in Conrad Trail, overland flow was generated much less frequently and then only locally. We conclude that soilscape features and microtopography are important controls of overland flow generation in these catchments. Our results contribute to the growing evidence that overland flow and forests are not a priori a contradiction in terms. (C) 2004 Elsevier B.V. All rights reserved}, language = {en} } @article{GrimmBehrensMaerkeretal.2008, author = {Grimm, Rosina and Behrens, T. and M{\"a}rker, Michael and Elsenbeer, Helmut}, title = {Soil organic carbon concentrations and stocks on Barro Colorado Island : digital soil mapping using random forests analysis}, issn = {0016-7061}, doi = {10.1016/j.geoderma.2008.05.008}, year = {2008}, language = {en} } @article{HasslerLarkMilneetal.2011, author = {Haßler, Sibylle Kathrin and Lark, Richard M. and Milne, A. E. and Elsenbeer, Helmut}, title = {Exploring the variation in soil saturated hydraulic conductivity under a tropical rainforest using the wavelet transform}, series = {European journal of soil science}, volume = {62}, journal = {European journal of soil science}, number = {6}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1351-0754}, doi = {10.1111/j.1365-2389.2011.01400.x}, pages = {891 -- 901}, year = {2011}, abstract = {Saturated hydraulic conductivity (Ks) of the soil is a key variable in the water cycle. For the humid tropics, information about spatial scales of Ks and their relation to soil types deduced from soil map units is of interest, as soil maps are often the only available data source for modelling. We examined the influence of soil map units on the mean and variation in Ks along a transect in a tropical rainforest using undisturbed soil cores at 06 and 612 cm depth. The Ks means were estimated with a linear mixed model fitted by residual maximum likelihood (REML), and the spatial variation in Ks was investigated with the maximum overlap discrete wavelet packet transform (MODWPT). The mean values of Ks did not differ between soil map units. The best wavelet packet basis for Ks at 06 cm showed stationarity at high frequencies, suggesting uniform small-scale influences such as bioturbation. There were substantial contributions to wavelet packet variance over the range of spatial frequencies and a pronounced low frequency peak corresponding approximately to the scale of soil map units. However, in the relevant frequency intervals no significant changes in wavelet packet variance were detected. We conclude that near-surface Ks is not dominated by static, soil-inherent properties for the examined range of soils. Several indicators from the wavelet packet analysis hint at the more dominant dynamic influence of biotic processes, which should be kept in mind when modelling soil hydraulic properties on the basis of soil maps.}, language = {en} } @misc{HowaldElsenbeerLaczkoetal.1995, author = {Howald, Markus and Elsenbeer, Helmut and Laczko, Endre and Schlunegger, Urs Peter}, title = {Capillary electrophoresis as a fast and universal tool in soil analysis}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16913}, year = {1995}, abstract = {Fast analysis of different species of molecules in soils is investigated by capillary electrophoresis (CE). Several CE techniques for the analysis of inorganic ions and carbohydrates have been tested. With regard to the intents of pedologists and the usually large number of soil analyses a bundle of CE systems is proposed, capable of effecting time-saving soil analyses. Adapted electrolyte systems recently published and new separation systems are described. Examples of the application of these methods to two different soil samples are presented.}, language = {en} } @article{NeillChavesBiggsetal.2011, author = {Neill, Christopher and Chaves, Joaqu{\´i}n E. and Biggs, Trent and Deegan, Linda A. and Elsenbeer, Helmut and Figueiredo, Ricardo O. and Germer, Sonja and Johnson, Mark S. and Lehmann, Johannes and Markewitz, Daniel and Piccolo, Marisa C.}, title = {Runoff sources and land cover change in the Amazon an end-member mixing analysis from small watersheds}, series = {Biogeochemistry}, volume = {105}, journal = {Biogeochemistry}, number = {1-3}, publisher = {Springer}, address = {Dordrecht}, issn = {0168-2563}, doi = {10.1007/s10533-011-9597-8}, pages = {7 -- 18}, year = {2011}, abstract = {The flowpaths by which water moves from watersheds to streams has important consequences for the runoff dynamics and biogeochemistry of surface waters in the Amazon Basin. The clearing of Amazon forest to cattle pasture has the potential to change runoff sources to streams by shifting runoff to more surficial flow pathways. We applied end-member mixing analysis (EMMA) to 10 small watersheds throughout the Amazon in which solute composition of streamwater and groundwater, overland flow, soil solution, throughfall and rainwater were measured, largely as part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia. We found a range in the extent to which streamwater samples fell within the mixing space determined by potential flowpath end-members, suggesting that some water sources to streams were not sampled. The contribution of overland flow as a source of stream flow was greater in pasture watersheds than in forest watersheds of comparable size. Increases in overland flow contribution to pasture streams ranged in some cases from 0\% in forest to 27-28\% in pasture and were broadly consistent with results from hydrometric sampling of Amazon forest and pasture watersheds that indicate 17- to 18-fold increase in the overland flow contribution to stream flow in pastures. In forest, overland flow was an important contribution to stream flow (45-57\%) in ephemeral streams where flows were dominated by stormflow. Overland flow contribution to stream flow decreased in importance with increasing watershed area, from 21 to 57\% in forest and 60-89\% in pasture watersheds of less than 10 ha to 0\% in forest and 27-28\% in pastures in watersheds greater than 100 ha. Soil solution contributions to stream flow were similar across watershed area and groundwater inputs generally increased in proportion to decreases in overland flow. Application of EMMA across multiple watersheds indicated patterns across gradients of stream size and land cover that were consistent with patterns determined by detailed hydrometric sampling.}, language = {en} } @article{NeillElsenbeerKruscheetal.2006, author = {Neill, Christopher and Elsenbeer, Helmut and Krusche, Alex V. and Lehmann, Johannes and Markewitz, Daniel and Figueiredo, Ricardo de O.}, title = {Hydrological and biogeochemical processes in a changing Amazon : results from small watershed studies and the large-scale biosphere-atmosphere experiment}, doi = {10.1002/Hyp.6210}, year = {2006}, abstract = {The Amazon Basin is the world's largest tropical forest region and one where rapid human changes to land cover have the potential to cause significant changes to hydrological and biogeochemical processes. The Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) is a multidisciplinary, multinational research program led by Brazil. The goal of LBA is to understand how the Amazon Basin functions as a regional entity in the earth system and how these functions are changing as a result of ongoing human activity. This compilation of nine papers focuses on a central LBA question in the area of nutrient dynamics and surface water chemistry-how do changes in land use alter fluxes of dissolved and particulate materials from uplands across riparian zones and down the channels of river corridors? These papers cover work conducted in small watersheds on a wide range of topics within the spirit and geographical focus area of LBA: water balance and runoff generation, nutrient transformations in riparian zones and stream channels, carbon fluxes in water moving from land to water and the influence of soils on flowpath structure and stream chemistry. Important new insights can be gained from these and other studies. Forest clearing for pastures results in a decrease in soil hydraulic conductivity that forces water into surficial flowpaths throughout most of the rainy season across wide regions of the Amazon. Riparian zones along small forest streams appear to be very effective in removing nitrate arriving from the uplands, while forest streams take up nitrate at very low rates, allowing them to travel downstream for long distances. Although substantial, the contribution of dissolved organic C (DOC) to the carbon flux from forests to streams appears to be lower than the flux of dissolved inorganic C that is subsequently outgassed as CO2. Remaining key challenges within LBA will be to synthesize existing data sets on river networks, soils, climate, land use and planned infrastructure for the Amazon to develop models capable of predicting hydrologic and biogeochemical fluxes at a variety of scales relevant to the development of strategies for sustainable management of the Amazon's remarkable forest, soil and freshwater resources.}, language = {en} } @article{ZeheElsenbeerLindenmaieretal.2007, author = {Zehe, Erwin and Elsenbeer, Helmut and Lindenmaier, Falk and Schulz, K. and Bl{\"o}schl, G{\"u}nter}, title = {Patterns of predictability in hydrological threshold systems}, issn = {0043-1397}, doi = {10.1029/2006wr005589}, year = {2007}, abstract = {[1] Observations of hydrological response often exhibit considerable scatter that is difficult to interpret. In this paper, we examine runoff production of 53 sprinkling experiments on the water-repellent soils in the southern Alps of Switzerland; simulated plot scale tracer transport in the macroporous soils at the Weiherbach site, Germany; and runoff generation data from the 2.3-km(2) Tannhausen catchment, Germany, that has cracking soils. The response at the three sites is highly dependent on the initial soil moisture state as a result of the threshold dynamics of the systems. A simple statistical model of threshold behavior is proposed to help interpret the scatter in the observations. Specifically, the model portrays how the inherent macrostate uncertainty of initial soil moisture translates into the scatter of the observed system response. The statistical model is then used to explore the asymptotic pattern of predictability when increasing the number of observations, which is normally not possible in a field study. Although the physical and chemical mechanisms of the processes at the three sites are different, the predictability patterns are remarkably similar. Predictability is smallest when the system state is close to the threshold and increases as the system state moves away from it. There is inherent uncertainty in the response data that is not measurement error but is related to the observability of the initial conditions.}, language = {en} } @article{ZimmermannGermerNeilletal.2008, author = {Zimmermann, Alexander and Germer, Sonja and Neill, Christopher and Krusche, Alex V. and Elsenbeer, Helmut}, title = {Spatio-temporal patterns of throughfall and solute deposition in an open tropical rain forest}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2008.07.028}, year = {2008}, language = {en} } @article{ZimmermannWilckeElsenbeer2007, author = {Zimmermann, Alexander and Wilcke, Wolfgang and Elsenbeer, Helmut}, title = {Spatial and temporal patterns of throughfall quantity and quality in a tropical montane forest in Ecuador}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2007.06.012}, year = {2007}, language = {en} } @article{ZimmermannZimmermannElsenbeer2009, author = {Zimmermann, Alexander and Zimmermann, Beate and Elsenbeer, Helmut}, title = {Rainfall redistribution in a tropical forest : spatial and temporal patterns}, issn = {0043-1397}, doi = {10.1029/2008WR007470}, year = {2009}, abstract = {The investigation of throughfall patterns has received considerable interest over the last decades. And yet, the geographical bias of pertinent previous studies and their methodologies and approaches to data analysis cast a doubt on the general validity of claims regarding spatial and temporal patterns of throughfall. We employed 220 collectors in a 1-ha plot of semideciduous tropical rain forest in Panama and sampled throughfall during a period of 14 months. Our analysis of spatial patterns is based on 60 data sets, whereas the temporal analysis comprises 91 events. Both data sets show skewed frequency distributions. When skewness arises from large outliers, the classical, nonrobust variogram estimator overestimates the sill variance and, in some cases, even induces spurious autocorrelation structures. In these situations, robust variogram estimation techniques offer a solution. Throughfall in our plot typically displayed no or only weak spatial autocorrelations. In contrast, temporal correlations were strong, that is, wet and dry locations persisted over consecutive wet seasons. Interestingly, seasonality and hence deciduousness had no influence on spatial and temporal patterns. We argue that if throughfall patterns are to have any explanatory power with respect to patterns of near-surface processes, data analytical artifacts must be ruled out lest spurious correlation be confounded with causality; furthermore, temporal stability over the domain of interest is essential.}, language = {en} } @article{ZimmermannElsenbeer2008, author = {Zimmermann, Beate and Elsenbeer, Helmut}, title = {Spatial and temporal variability of soil saturated hydraulic conductivity in gradients of disturbance}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2008.07.027}, year = {2008}, language = {en} } @article{ZimmermannElsenbeer2009, author = {Zimmermann, Beate and Elsenbeer, Helmut}, title = {The near-surface hydrological consequences of disturbance and recovery : a simulation study}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2008.10.016}, year = {2009}, abstract = {Changes in soil hydraulic properties following ecosystem disturbances can become relevant for regional water cycles depending on the prevailing rainfall regime. In a tropical montane rainforest ecosystem in southern Ecuador, plot- scale investigations revealed that man-made disturbances were accompanied by a decrease in mean saturated hydraulic conductivity (Ks), whereas mean Ks of two different aged landslides was undistinguishable from the reference forest. Ks spatial structure weakened after disturbances in the topsoil. We used this spatial-temporal information combined with local rain intensities to assess the probability of impermeable soil layers under undisturbed, disturbed, and regenerating land-cover types. We furthermore compared the Ecuadorian man-made disturbance cycle with a similar land-use sequence in a tropical lowland rainforest region in Brazil. The studied montane rainforest is characterized by prevailing vertical flowpaths in the topsoil, whereas larger rainstorms in the study area potentially result in impermeable layers below 20 cm depth. In spite of the low frequency of such higher-intensity events, they transport a high portion of the annual runoff and may therefore significant for the regional water cycle. Hydrological flowpaths under two studied landslides are similar to the natural forest except for a somewhat higher probability of impermeable layer formation in the topsoil of the 2-year-old landslide. In contrast, human disturbances likely affect near-surface hydrology. Under a pasture and a young fallow, impermeable layers potentially develop already in the topsoil for larger rain events. A 10-year-old fallow indicates regeneration towards the original vertical flowpaths, though the land-use signal was still detectable. The consequences of land-cover change on near-surface hydrological behaviour are of similar magnitude in the tropical montane and the lowland rainforest region. This similarity can be explained by a more pronounced drop of soil permeability after pasture establishment in the montane rainforest region in spite of the prevailing much lower rain intensities.}, language = {en} } @article{ZimmermannElsenbeerdeMoraes2006, author = {Zimmermann, Beate and Elsenbeer, Helmut and de Moraes, Jorge M.}, title = {The influence of land-use changes on soil hydraulic properties : implications for runoff generation}, issn = {0378-1127}, doi = {10.1016/j.foreco.2005.10.070}, year = {2006}, language = {en} } @article{ZimmermannZeheHartmannetal.2008, author = {Zimmermann, Beate and Zehe, Erwin and Hartmann, N. K. and Elsenbeer, Helmut}, title = {Analyzing spatial data : an assessment of assumptions, new methods, and uncertainty using soil hydraulic data}, issn = {0043-1397}, year = {2008}, language = {en} }