@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}
}