McHorney Richard

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Conversion to soy on the Amazonian agricultural frontier increases streamflow without affecting stormflow dynamics

2011-01 , Hayhoe, Shelby J. , Neill, Christopher , Porder, Stephen , McHorney, Richard , LeFebvre, Paul , Coe, Michael T. , Elsenbeer, Helmut , Krusche, Alex V.

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, which remain relatively unstudied. 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 to 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 one 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.

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Buzzards Bay Water Quality Data from the Buzzards Bay Coalition’s Baywatchers Program 1992-2020

2021-07-09 , Jakuba, Rachel W. , Williams, Tony , Neill, Christopher , Costa, Joseph E. , McHorney, Richard , Scott, Lindsay , Howes, Brian L. , Ducklow, Hugh W. , Erickson, Matthew , Rasmussen, Mark

The Buzzards Bay Coalition’s Baywatchers Monitoring Program collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2020. Baywatchers monitoring data document nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality. The Readme, STN_EQUIV, Stations and Methods, S_D for WFH, and Acknowledge tabs were updated and corrections were made for Time and POC on 2018 Upper Bay samples and deleted CH1 from sonde method column where no CHL data existed, moved words like "sample lost" from Chl and Pheo data columns to comments column.

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Deep soils modify environmental consequences of increased nitrogen fertilizer use in intensifying Amazon agriculture

2018-09-07 , Jankowski, KathiJo , Neill, Christopher , Davidson, Eric A. , Macedo, Marcia N. , Costa, Ciniro , Galford, Gillian L. , Maracahipes Santos, Leonardo , LeFebvre, Paul , Nunes, Darlisson , Cerri, Carlos E. P. , McHorney, Richard , O’Connell, Christine , Coe, Michael T.

Agricultural intensification offers potential to grow more food while reducing the conversion of native ecosystems to croplands. However, intensification also risks environmental degradation through emissions of the greenhouse gas nitrous oxide (N2O) and nitrate leaching to ground and surface waters. Intensively-managed croplands and nitrogen (N) fertilizer use are expanding rapidly in tropical regions. We quantified fertilizer responses of maize yield, N2O emissions, and N leaching in an Amazon soybean-maize double-cropping system on deep, highly-weathered soils in Mato Grosso, Brazil. Application of N fertilizer above 80 kg N ha−1 yr−1 increased maize yield and N2O emissions only slightly. Unlike experiences in temperate regions, leached nitrate accumulated in deep soils with increased fertilizer and conversion to cropping at N fertilization rates >80 kg N ha−1, which exceeded maize demand. This raises new questions about the capacity of tropical agricultural soils to store nitrogen, which may determine when and how much nitrogen impacts surface waters.

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Dataset

Buzzards Bay Water Quality Data from the Buzzards Bay Coalition’s Baywatchers Program 1992-2018 December 2020 version

2020-12-08 , Jakuba, Rachel W. , Williams, Tony , Neill, Christopher , Costa, Joseph E. , McHorney, Richard , Scott, Lindsay , Howes, Brian L. , Ducklow, Hugh W. , Erickson, Matthew , Rasmussen, Mark

The Buzzards Bay Coalition’s Baywatchers Monitoring Program collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2018. Baywatchers monitoring data document nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality. The Readme, STN_EQUIV, Stations and Methods, S_D for WFH, and Acknowledge tabs were updated and corrections were made for Time and POC on 2018 Upper Bay samples and deleted CH1 from sonde method column where no CHL data existed, moved words like "sample lost" from Chl and Pheo data columns to comments column.

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Buzzards Bay Water Quality Data from the Buzzards Bay Coalition’s Baywatchers Program 1992-2018 August 2020 version

2020-08-28 , Jakuba, Rachel W. , Williams, Tony , Neill, Christopher , Costa, Joseph E. , McHorney, Richard , Scott, Lindsay , Howes, Brian L. , Ducklow, Hugh W. , Erickson, Matthew , Rasmussen, Mark

The Buzzards Bay Coalition’s Baywatchers Monitoring Program collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2018. Baywatchers monitoring data document nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality. The Readme, STN_EQUIV, Stations and Methods, S_D for WFH, and Acknowledge tabs were updated and corrections were made for Time and POC on 2018 Upper Bay samples and deleted CH1 from sonde method column where no CHL data existed, moved words like "sample lost" from Chl and Pheo data columns to comments column.

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Article

Solute and sediment export from Amazon forest and soybean headwater streams

2017-01-04 , Riskin, Shelby H. , Neill, Christopher , Jankowski, KathiJo , Krusche, Alex V. , McHorney, Richard , Elsenbeer, Helmut , Macedo, Marcia N. , Nunes, Darlisson , Porder, Stephen

Intensive cropland agriculture commonly increases streamwater solute concentrations and export from small watersheds. In recent decades, the lowland tropics have become the world's largest and most important region of cropland expansion. Although the effects of intensive cropland agriculture on streamwater chemistry and watershed export have been widely studied in temperate regions, their effects in tropical regions are poorly understood. We sampled seven headwater streams draining watersheds in forest (n = 3) or soybeans (n = 4) to examine the effects of soybean cropping on stream solute concentrations and watershed export in a region of rapid soybean expansion in the Brazilian state of Mato Grosso. We measured stream flows and concentrations of NO3−, PO43−, SO42−, Cl−, NH4+, Ca2+, Mg2+, Na+, K+, Al3+, Fe3+, and dissolved organic carbon (DOC) biweekly to monthly to determine solute export. We also measured stormflows and stormflow solute concentrations in a subset of watersheds (two forest, two soybean) during two/three storms, and solutes and δ18O in groundwater, rainwater, and throughfall to characterize watershed flowpaths. Concentrations of all solutes except K+ varied seasonally in streamwater, but only Fe3+ concentrations differed between land uses. The highest streamwater and rainwater solute concentrations occurred during the peak season of wildfires in Mato Grosso, suggesting that regional changes in atmospheric composition and deposition influence seasonal stream solute concentrations. Despite no concentration differences between forest and soybean land uses, annual export of NH4+, PO43−, Ca2+, Fe3+, Na+, SO42−, DOC, and TSS were significantly higher from soybean than forest watersheds (5.6-fold mean increase). This increase largely reflected a 4.3-fold increase in water export from soybean watersheds. Despite this increase, total solute export per unit watershed area (i.e., yield) remained low for all watersheds (<1 kg NO3− N·ha−1·yr−1, <2.1 kg NH4+-N·ha−1·yr−1, <0.2 kg PO43−-P·ha−1·yr−1, <1.5 kg Ca2+·ha−1·yr−1). Responses of both streamflows and solute concentrations to crop agriculture appear to be controlled by high soil hydraulic conductivity, groundwater-dominated hydrologic flowpaths on deep soils, and the absence of nitrogen fertilization. To date, these factors have buffered streams from the large increases in solute concentrations that often accompany intensive croplands in other locations.

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Water quality measurements in Buzzards Bay by the Buzzards Bay Coalition Baywatchers Program from 1992 to 2018

2021-03-05 , Jakuba, Rachel W. , Williams, Tony , Neill, Christopher , Costa, Joseph E. , McHorney, Richard , Scott, Lindsay , Howes, Brian L. , Ducklow, Hugh W. , Erickson, Matthew , Rasmussen, Mark

The Buzzards Bay Coalition’s Baywatchers Monitoring Program (Baywatchers) collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2018. Baywatchers documents nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality.

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Preprint

Distribution, species composition and management implications of seed banks in southern New England coastal plain ponds

2008-12 , Neill, Christopher , Bezerra, Maira Ometto , McHorney, Richard , O’Dea, Claire B.

Buried seeds that germinate during periods of low water or water level drawdown can play important roles in shaping plant community composition, community dynamics and species richness in ecosystems with fluctuating water levels. Northeastern US coastal plain ponds have fluctuating water levels and contain a characteristic shoreline flora that contains many rare plants. The objectives of this study were to: (1) test whether geographically distant ponds in Cape Cod and Martha’s Vineyard had distinct seed banks, (2) determine if hydrologic status as permanent and ephemeral ponds led to differences in seed banks, and (3) examine seed diversity and seed abundance across gradients of shoreline elevations and sediment characteristics. Viable seeds of 45 plant species were identified from 9 ponds. Native species dominated pond-shore seed banks and made up 89 to 100% of all species. There was high overlap in seed bank composition across hydrological classes and geographic regions. One hydrological class captured 73-76% of total species and one geographical region captured 69-78% of the total species recovered from the entire suite of seed bank samples. Seeds were relatively evenly distributed along the shorelines of ephemeral ponds but seed diversity and abundance were lower at low elevations in permanent ponds. Results suggest that strategies to protect pond shorelines to capture maximum diversity of coastal plain pond plants contained in pond sediment seed banks should be implemented across pond hydrologic classes and across a wide geographic area. Shoreline seed distributions indicate that ground-water withdrawals or climate changes that lower pond water levels in permanent ponds will reduce the diversity and abundance of plants recovered from seed banks by shifting water levels to a shoreline zone of high sediment organic matter where seed densities are lower. This effect will be much less in ephemeral ponds where seed diversity and abundance on pond bottoms was high.

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Buzzards Bay Water Quality Data from the Buzzards Bay Coalition’s Baywatchers Program 1992-2018

2020-05-04 , Jakuba, Rachel W. , Williams, Tony , Neill, Christopher , Costa, Joseph E. , McHorney, Richard , Scott, Lindsay , Howes, Brian L. , Ducklow, Hugh W. , Erickson, Matthew , Rasmussen, Mark

The Buzzards Bay Coalition’s Baywatchers Monitoring Program collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2018. Baywatchers monitoring data document nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality.

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