TY - GEN A1 - Chaves, Joaquín E. A1 - Neill, Christopher A1 - Germer, Sonja A1 - Neto, Sergio Gouveia A1 - Krusche, Alex V. A1 - Bonilla, Adriana Castellanos A1 - Elsenbeer, Helmut T1 - Nitrogen transformations in flowpaths leading from soils to streams in Amazon forest and pasture Y1 - 2009 UR - http://www.springerlink.com/content/101552 U6 - https://doi.org/10.1007/s10021-009-9270-4 SN - 1432-9840 ER - TY - JOUR A1 - Germer, Sonja A1 - Neill, Christopher A1 - Vetter, Tobias A1 - Chaves, Joaquín E. A1 - Krusche, Alex V. A1 - Elsenbeer, Helmut T1 - Implications of long-term land-use change for the hydrology and solute budgets of small catchments in Amazonia N2 - 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. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00221694 U6 - https://doi.org/10.1016/j.jhydrol.2008.11.013 SN - 0022-1694 ER - TY - JOUR A1 - Zimmermann, Alexander A1 - Zimmermann, Beate A1 - Elsenbeer, Helmut T1 - Rainfall redistribution in a tropical forest : spatial and temporal patterns N2 - 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. Y1 - 2009 UR - http://www.agu.org/pubs/crossref/2009/2008WR007470.shtml U6 - https://doi.org/10.1029/2008WR007470 SN - 0043-1397 ER - TY - JOUR A1 - Zimmermann, Beate A1 - Elsenbeer, Helmut T1 - The near-surface hydrological consequences of disturbance and recovery : a simulation study N2 - 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. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00221694 U6 - https://doi.org/10.1016/j.jhydrol.2008.10.016 SN - 0022-1694 ER -