TY - JOUR A1 - Neill, Christopher A1 - Chaves, Joaquín E. A1 - Biggs, Trent A1 - Deegan, Linda A. A1 - Elsenbeer, Helmut A1 - Figueiredo, Ricardo O. A1 - Germer, Sonja A1 - Johnson, Mark S. A1 - Lehmann, Johannes A1 - Markewitz, Daniel A1 - Piccolo, Marisa C. T1 - Runoff sources and land cover change in the Amazon an end-member mixing analysis from small watersheds JF - Biogeochemistry N2 - 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. KW - Cattle pasture KW - Deforestation KW - Flowpaths KW - Principal components analysis KW - Overland flow KW - Soil solution Y1 - 2011 U6 - https://doi.org/10.1007/s10533-011-9597-8 SN - 0168-2563 VL - 105 IS - 1-3 SP - 7 EP - 18 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Germer, Sonja A1 - Zimmermann, Alexander A1 - Neill, Christopher A1 - Krusche, Alex V. A1 - Elsenbeer, Helmut T1 - Disproportionate single-species contribution to canopy-soil nutrient flux in an Amazonian rainforest JF - Forest ecology and management N2 - Rainfall, throughfall and stemflow were monitored on an event basis in an undisturbed open tropical rainforest with a large number of palm trees located in the southwestern Amazon basin of Brazil. Stemflow samples were collected from 24 trees with a diameter at breast height (DBH) > 5 cm, as well as eight young and four full-grown babassu palms (Attalea speciosa Mart.) for 5 weeks during the peak of the wet season. We calculated rainfall, throughfall and stemflow concentrations and fluxes of Na+, K+, Ca2+, Mg2+,, Cl-, SO42-, NO3- and H+ and stemflow volume-weighted mean concentrations and fluxes for three size classes of broadleaf trees and three size classes of palms. The concentrations of most solutes were higher in stemflow than in rainfall and increased with increasing tree and palm size. Concentration enrichments from rainfall to stemflow and throughfall were particularly high (81-fold) for NO3-. Stemflow fluxes of NO3- and H+ exceeded throughfall fluxes but stemflow fluxes of other solutes were less than throughfall fluxes. Stemflow solute fluxes to the forest soil were dominated by fluxes on babassu palms, which represented only 4% of total stem number and 10% of total basal area. For NO3-, stemflow contributed 51% of the total mass of nitrogen delivered to the forest floor (stemflow + throughfall) and represented more than a 2000-fold increase in NO3- flux compared what would have been delivered by rainfall alone on the equivalent area. Because these highly localized fluxes of both water and NO3- persist in time and space, they have the potential to affect patterns of soil moisture, microbial populations and other features of soil biogeochemistry conducive to the creation of hotspots for nitrogen leaching and denitrification, which could amount to an important fraction of total ecosystem fluxes. Because these hotspots occur over very small areas, they have likely gone undetected in previous studies and need to be considered as an important feature of the biogeochemistry of palm-rich tropical forest. KW - Stemflow KW - Throughfall KW - DBH KW - Open tropical rain forest KW - Babassu palm (Attalea speciosa Mart. synonym: Orbignya phalerata Mart.) KW - Amazonia Y1 - 2012 U6 - https://doi.org/10.1016/j.foreco.2011.11.041 SN - 0378-1127 VL - 267 IS - 2 SP - 40 EP - 49 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Germer, Sonja A1 - Neill, Christopher A1 - Krusche, Alex V. A1 - Elsenbeer, Helmut T1 - Influence of land-use change on near-surface hydrological processes : undisturbed forest to pasture N2 - 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. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00221694 U6 - https://doi.org/10.1016/j.jhydrol.2009.11.022 SN - 0022-1694 ER - TY - JOUR A1 - Germer, Sonja A1 - Neill, Christopher A1 - Krusche, Alex V. A1 - Neto, Sergio Gouveia A1 - Elsenbeer, Helmut T1 - Seasonal and within-event dynamics of rainfall and throughfall chemistry in an open tropical rainforest in Rondônia, Brazil N2 - 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. Y1 - 2007 UR - http://www.springerlink.com/content/100244 U6 - https://doi.org/10.1007/s10533-007-9152-9 SN - 0168-2563 ER - 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 - Chaves, Joaquín E. A1 - Neill, Christopher A1 - Germer, Sonja A1 - Neto, Sérgio Gouveia A1 - Krusche, Alex V. A1 - Elsenbeer, Helmut T1 - Land management impacts on runoff sources in small amazon watersheds Y1 - 2008 UR - http://www3.interscience.wiley.com/journal/4125/home?CRETRY=1&SRETRY=0 U6 - https://doi.org/10.1002/hyp.6803 SN - 0885-6087 ER - TY - JOUR A1 - Zimmermann, Alexander A1 - Germer, Sonja A1 - Neill, Christopher A1 - Krusche, Alex V. A1 - Elsenbeer, Helmut T1 - Spatio-temporal patterns of throughfall and solute deposition in an open tropical rain forest Y1 - 2008 UR - http://www.sciencedirect.com/science/journal/00221694 U6 - https://doi.org/10.1016/j.jhydrol.2008.07.028 SN - 0022-1694 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 - Germer, Sonja A1 - Elsenbeer, Helmut A1 - de Moraes, Jorge M. T1 - Throughfall and temporal trends of rainfall redistribution in an open tropical rainforest, south-western Amazonia (Rondônia, Brazil) Y1 - 2006 UR - http://www.hydrology-and-earth-system-sciences.net/index.html U6 - https://doi.org/10.5194/hess-10-383-2006 SN - 1027-5606 ER -