@article{NeillJankowskiBrandoetal.2017, author = {Neill, Christopher and Jankowski, KathiJo and Brando, Paulo M. and Coe, Michael T. and Deegan, Linda A. and Macedo, Marcia N. and Riskin, Shelby H. and Porder, Stephen and Elsenbeer, Helmut and Krusche, Alex V.}, title = {Surprisingly Modest Water Quality Impacts From Expansion and Intensification of Large-Sscale Commercial Agriculture in the Brazilian Amazon-Cerrado Region}, series = {Tropical conservation science}, volume = {10}, journal = {Tropical conservation science}, publisher = {Sage Publ.}, address = {Thousand Oaks}, issn = {1940-0829}, doi = {10.1177/1940082917720669}, pages = {5}, year = {2017}, abstract = {Large-scale commercial cropping of soybeans expanded in the tropical Amazon and Cerrado biomes of Brazil after 1990. More recently, cropping intensified from single-cropping of soybeans to double-cropping of soybeans with corn or cotton. Cropland expansion and intensification, and the accompanying use of mineral fertilizers, raise concerns about whether nutrient runoff and impacts to surface waters will be similar to those experienced in commercial cropland regions at temperate latitudes. We quantified water infiltration through soils, water yield, and streamwater chemistry in watersheds draining native tropical forest and single-and double-cropped areas on the level, deep, highly weathered soils where cropland expansion and intensification typically occurs. Although water yield increased four-fold from croplands, streamwater chemistry remained largely unchanged. Soil characteristics exerted important control over the movement of nitrogen (N) and phosphorus (P) into streams. High soil infiltration rates prevented surface erosion and movement of particulate P, while P fixation in surface soils restricted P movement to deeper soil layers. Nitrogen retention in deep soils, likely by anion exchange, also appeared to limit N leaching and export in streamwater from both single-and double-cropped watersheds that received nitrogen fertilizer. These mechanisms led to lower streamwater P and N concentrations and lower watershed N and P export than would be expected, based on studies from temperate croplands with similar cropping and fertilizer application practices.}, language = {en} } @article{NeillCoeRiskinetal.2013, author = {Neill, Christopher and Coe, Michael T. and Riskin, Shelby H. and Krusche, Alex V. and Elsenbeer, Helmut and Macedo, Marcia N. and McHorney, Richard and Lefebvre, Paul and Davidson, Eric A. and Scheffler, Raphael and Figueira, Adelaine Michela e Silva and Porder, Stephen and Deegan, Linda A.}, title = {Watershed responses to Amazon soya bean cropland expansion and intensification}, series = {Philosophical transactions of the Royal Society of London : B, Biological sciences}, volume = {368}, journal = {Philosophical transactions of the Royal Society of London : B, Biological sciences}, number = {1619}, publisher = {Royal Society}, address = {London}, issn = {0962-8436}, doi = {10.1098/rstb.2012.0425}, pages = {7}, year = {2013}, abstract = {The expansion and intensification of soya bean agriculture in southeastern Amazonia can alter watershed hydrology and biogeochemistry by changing the land cover, water balance and nutrient inputs. Several new insights on the responses of watershed hydrology and biogeochemistry to deforestation in Mato Grosso have emerged from recent intensive field campaigns in this region. Because of reduced evapotranspiration, total water export increases threefold to fourfold in soya bean watersheds compared with forest. However, the deep and highly permeable soils on the broad plateaus on which much of the soya bean cultivation has expanded buffer small soya bean watersheds against increased stormflows. Concentrations of nitrate and phosphate do not differ between forest or soya bean watersheds because fixation of phosphorus fertilizer by iron and aluminium oxides and anion exchange of nitrate in deep soils restrict nutrient movement. Despite resistance to biogeochemical change, streams in soya bean watersheds have higher temperatures caused by impoundments and reduction of bordering riparian forest. In larger rivers, increased water flow, current velocities and sediment flux following deforestation can reshape stream morphology, suggesting that cumulative impacts of deforestation in small watersheds will occur at larger scales.}, language = {en} } @article{GermerZimmermannNeilletal.2012, author = {Germer, Sonja and Zimmermann, Alexander and Neill, Christopher and Krusche, Alex V. and Elsenbeer, Helmut}, title = {Disproportionate single-species contribution to canopy-soil nutrient flux in an Amazonian rainforest}, series = {Forest ecology and management}, volume = {267}, journal = {Forest ecology and management}, number = {2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0378-1127}, doi = {10.1016/j.foreco.2011.11.041}, pages = {40 -- 49}, year = {2012}, abstract = {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.}, language = {en} } @article{BaeseElsenbeerNeilletal.2012, author = {B{\"a}se, Frank and Elsenbeer, Helmut and Neill, Christopher and Krusche, Alex V.}, title = {Differences in throughfall and net precipitation between soybean and transitional tropical forest in the southern Amazon, Brazil}, series = {Agriculture, ecosystems \& environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere}, volume = {159}, journal = {Agriculture, ecosystems \& environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-8809}, doi = {10.1016/j.agee.2012.06.013}, pages = {19 -- 28}, year = {2012}, abstract = {The expansion of soybean cultivation into the Amazon in Brazil has potential hydrological effects at local to regional scales. To determine the impacts of soybean agriculture on hydrology, a comparison of net precipitation (throughfall, stemflow) in undisturbed tropical forest and soybean fields on the southern edge of the Amazon Basin in the state of Mato Grosso is needed. This study measured throughfall with troughs and stemflow with collar collectors during two rainy seasons. The results showed that in forest 91.6\% of rainfall was collected as throughfall and 0.3\% as stemflow, while in soybean fields with two-month old plants, 46.2\% of rainfall was collected as throughfall and 9.0\% as stemflow. Hence, interception of precipitation in soybean fields was far greater than in intact forests. Differences in throughfall, stemflow and net precipitation were found to be mainly associated with differences in plant structure and stem density in transitional forest and soybean cropland. Because rainfall interception in soybean fields is higher than previously believed and because both the area of cropland and the frequency of crop cycles (double cropping) are increasing rapidly, interception needs to be reconsidered in regional water balance models when consequences of land cover changes are analyzed in the Amazon soybean frontier region. Based on the continued expansion of soybean fields across the landscape and the finding that net precipitation is lower in soy agriculture, a reduction in water availability in the long term can be assumed.}, language = {en} } @article{HayhoeNeillPorderetal.2011, author = {Hayhoe, Shelby J. and Neill, Christopher and Porder, Stephen and McHorney, Richard and Lefebvre, Paul and Coe, Michael T. and Elsenbeer, Helmut and Krusche, Alex V.}, title = {Conversion to soy on the Amazonian agricultural frontier increases streamflow without affecting stormflow dynamics}, series = {Global change biology}, volume = {17}, journal = {Global change biology}, number = {5}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1354-1013}, doi = {10.1111/j.1365-2486.2011.02392.x}, pages = {1821 -- 1833}, year = {2011}, abstract = {Large-scale soy agriculture in the southern Brazilian Amazon now rivals deforestation for pasture as the region's predominant form of land use change. Such landscape-level change can have substantial consequences for local and regional hydrology, but these effects remain relatively unstudied in this ecologically and economically important region. We examined how the conversion to soy agriculture influences water balances and stormflows using stream discharge (water yields) and the timing of discharge (stream hydrographs) in small (2.5-13.5 km2) forested and soy headwater watersheds in the Upper Xingu Watershed in the state of Mato Grosso, Brazil. We monitored water yield for 1 year in three forested and four soy watersheds. Mean daily water yields were approximately four times higher in soy than forested watersheds, and soy watersheds showed greater seasonal variability in discharge. The contribution of stormflows to annual streamflow in all streams was low (< 13\% of annual streamflow), and the contribution of stormflow to streamflow did not differ between land uses. If the increases in water yield observed in this study are typical, landscape-scale conversion to soy substantially alters water-balance, potentially altering the regional hydrology over large areas of the southern Amazon.}, language = {en} } @article{SchefflerNeillKruscheetal.2011, author = {Scheffler, Raphael and Neill, Christopher and Krusche, Alex V. and Elsenbeer, Helmut}, title = {Soil hydraulic response to land-use change associated with the recent soybean expansion at the Amazon agricultural frontier}, series = {Agriculture, ecosystems \& environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere}, volume = {144}, journal = {Agriculture, ecosystems \& environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere}, number = {1}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-8809}, doi = {10.1016/j.agee.2011.08.016}, pages = {281 -- 289}, year = {2011}, abstract = {Clearing for large-scale soy production and the displacement of cattle-breeding by soybeans are major features of land-use change in the lowland Amazon that can alter hydrologic properties of soils and the runoff generation over large areas. We measured infiltrability and saturated hydraulic conductivity (Ksat) under natural forest, pasture, and soybeans on Oxisols in a region of rapid soybean expansion in Mato Grosso, Brazil. The forest-pasture conversion reduced infiltrability from 1258 to 100 mm/h and Ksat at all depths. The pasture-soy conversion increased infiltrability from 100 to 469 mm/h (attributed to shallow disking), did not affect Ksat at 12.5 cm, but decreased Ksat at 30 cm from 122 to 80 mm/h, suggesting that soybean cultivation enhances subsoil compaction. Permeability decreased markedly with depth under forest, did not change under pasture, and averaged out at one fourth the forest value under soybeans with a similar pattern of anisotropy. Comparisons of permeability with rainfall intensities indicated that land-use change did not alter the predominantly vertical water movement within the soil. We conclude that this landscape is well buffered against land-use changes regarding near-surface hydrology, even though short-lived ponding and perched water tables may occur locally during high-intensity rainfall on pastures and under soybeans.}, 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} } @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{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{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} }