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  - 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  - 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  -