title: Watershed responses to Amazon soya bean cropland expansion and intensification.
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.
authors.affiliation: The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA. cneill@mbl.edu
authors.forename: Christopher
authors.initials: C
authors.lastname: Neill
authors.forename: Michael T
authors.initials: MT
authors.lastname: Coe
authors.forename: Shelby H
authors.initials: SH
authors.lastname: Riskin
authors.forename: Alex V
authors.initials: AV
authors.lastname: Krusche
authors.forename: Helmut
authors.initials: H
authors.lastname: Elsenbeer
authors.forename: Marcia N
authors.initials: MN
authors.lastname: Macedo
authors.forename: Richard
authors.initials: R
authors.lastname: McHorney
authors.forename: Paul
authors.initials: P
authors.lastname: Lefebvre
authors.forename: Eric A
authors.initials: EA
authors.lastname: Davidson
authors.forename: Raphael
authors.initials: R
authors.lastname: Scheffler
authors.forename: Adelaine Michela e Silva
authors.initials: AM
authors.lastname: Figueira
authors.forename: Stephen
authors.initials: S
authors.lastname: Porder
authors.forename: Linda A
authors.initials: LA
authors.lastname: Deegan
mesh_terms: D000383:Agriculture / Q000379:methods*; D001938:Brazil; D003247:Conservation of Natural Resources / Q000379:methods; D018556:Crops, Agricultural / Q000254:growth & development*; D017753:Ecosystem; D062070:Hydrology; D009566:Nitrates / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry; D045483:Rivers / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D013025:Glycine max / Q000254:growth & development*; D013696:Temperature; D060753:Water Quality
chemical_list: D009566:Nitrates; D012987:Soil; D010758:Phosphorus