Ecosystems Center
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The Ecosystems Center carries out research in ecosystems that range from the Arctic to the Antarctic, from Brazil to Martha’s Vineyard. In the Alaskan Arctic, scientists study the effect of warmer temperatures on tundra, stream and lake ecosystems. On the Arctic rivers of Eurasia, they measure how freshwater discharge is changing as the climate warms. On the western Antarctic peninsula, research focuses on the responses of the marine coastal ecosystem to rapid climate warming. In the western Amazon in Brazil, researchers assess how much the clearing of tropical forests will change the amount of greenhouse gas released into the atmosphere, while on the island of Martha’s Vineyard, scientists used controlled burns to restore coastal ecosystems. In central Massachusetts and in Abisko, Sweden, soil warming experiments are conducted to assess the forest’s response to climate warming. In northeastern Massachusetts, scientists study how changes in rural land use and urban development affect the flow of nutrients and organic matter into New England estuaries. In Boston Harbor, they measure the transfer of nitrogen from sediments to the water column as the harbor recovers from decades of sewage addition.
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Browsing Ecosystems Center by Subject "Agriculture"
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PreprintGlobal economic effects of changes in crops, pasture, and forests due to changing climate, carbon dioxide, and ozone( 2006-01) Reilly, John M. ; Paltsev, Sergey ; Felzer, Benjamin S. ; Wang, X. ; Kicklighter, David W. ; Melillo, Jerry M. ; Prinn, Ronald G. ; Sarofim, Marcus C. ; Sokolov, Andrei P. ; Wang, C.Multiple environmental changes will have consequences for global vegetation. To the extent that crop yields and pasture and forest productivity are affected there can be important economic consequences. We examine the combined effects of changes in climate, increases in carbon dioxide, and changes in tropospheric ozone on crop, pasture, and forest lands and the consequences for the global and regional economies. We examine scenarios where there is limited or little effort to control these substances, and policy scenarios that limit emissions of CO2 and ozone precursors. We find the effects of climate and CO2 to be generally positive, and the effects of ozone to be very detrimental. Unless ozone is strongly controlled damage could offset CO2 and climate benefits. We find that resource allocation among sectors in the economy, and trade among countries, can strongly affect the estimate of economic effect in a country.
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ArticleModeling nitrous oxide emissions from large-scale intensive cropping systems in the southern Amazon(Frontiers Media, 2021-12-10) Costa, Ciniro ; Galford, Gillian L. ; Coe, Michael T. ; Macedo, Marcia N. ; Jankowski, KathiJo ; O’Connell, Christine ; Neill, ChristopherNitrogen (N) fertilizer use is rapidly intensifying on tropical croplands and has the potential to increase emissions of the greenhouse gas, nitrous oxide (N2O). Since about 2005 Mato Grosso (MT), Brazil has shifted from single-cropped soybeans to double-cropping soybeans with maize, and now produces 1.5% of the world's maize. This production shift required an increase in N fertilization, but the effects on N2O emissions are poorly known. We calibrated the process-oriented biogeochemical DeNitrification-DeComposition (DNDC) model to simulate N2O emissions and crop production from soybean and soybean-maize cropping systems in MT. After model validation with field measurements and adjustments for hydrological properties of tropical soils, regional simulations suggested N2O emissions from soybean-maize cropland increased almost fourfold during 2001–2010, from 1.1 ± 1.1 to 4.1 ± 3.2 Gg 1014 N-N2O. Model sensitivity tests showed that emissions were spatially and seasonably variable and especially sensitive to soil bulk density and carbon content. Meeting future demand for maize using current soybean area in MT might require either (a) intensifying 3.0 million ha of existing single soybean to soybean-maize or (b) increasing N fertilization to ~180 kg N ha−1 on existing 2.3 million ha of soybean-maize area. The latter strategy would release ~35% more N2O than the first. Our modifications of the DNDC model will improve estimates of N2O emissions from agricultural production in MT and other tropical areas, but narrowing model uncertainty will depend on more detailed field measurements and spatial data on soil and cropping management.
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ArticleRegional differences in phosphorus budgets in intensive soybean agriculture(University of California Press, 2013-01) Riskin, Shelby H. ; Porder, Stephen ; Schipanski, Meagan E. ; Bennett, Elena M. ; Neill, ChristopherFertilizer-intensive agriculture has been integral to increasing food production over the past half century but has been accompanied by environmental costs. We use case studies of phosphorus fertilizer use in the world’s most productive soybean-growing regions, Iowa (United States), Mato Grosso (Brazil), and Buenos Aires (Argentina), to examine influences of management and soil type on agriculture’s most prevalent phosphorusrelated environmental consequences: eutrophication and consumption of Earth’s finite phosphorus reserves. With increasing phosphorus inputs, achieving high yields on tropical soils with high phosphorus-binding capacity is becoming more common. This system has low eutrophication risks but increases demands on phosphorus supplies. In contrast, production in traditional breadbaskets, on soils with lower phosphorus-binding capacities, is being sustained with decreasing phosphorus inputs. However, in these regions, historical overuse of phosphorus may mean continued eutrophication risk even as pressures on phosphorus reserves diminish. We focus here on soybean production but illustrate how achieving sustainable agriculture involves an intricate optimization of local, regional, and global considerations.
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ArticleSoil carbon dynamics in soybean cropland and forests in Mato Grosso, Brazil(John Wiley & Sons, 2018-01-05) Nagy, R. Chelsea ; Porder, Stephen ; Brando, Paulo ; Davidson, Eric A. ; Figueira, Adelaine Michela e Silva ; Neill, Christopher ; Riskin, Shelby H. ; Trumbore, Susan E.Climate and land use models predict that tropical deforestation and conversion to cropland will produce a large flux of soil carbon (C) to the atmosphere from accelerated decomposition of soil organic matter (SOM). However, the C flux from the deep tropical soils on which most intensive crop agriculture is now expanding remains poorly constrained. To quantify the effect of intensive agriculture on tropical soil C, we compared C stocks, radiocarbon, and stable C isotopes to 2 m depth from forests and soybean cropland created from former pasture in Mato Grosso, Brazil. We hypothesized that soil disturbance, higher soil temperatures (+2°C), and lower OM inputs from soybeans would increase soil C turnover and deplete C stocks relative to nearby forest soils. However, we found reduced C concentrations and stocks only in surface soils (0–10 cm) of soybean cropland compared with forests, and these differences could be explained by soil mixing during plowing. The amount and Δ14C of respired CO2 to 50 cm depth were significantly lower from soybean soils, yet CO2 production at 2 m deep was low in both forest and soybean soils. Mean surface soil δ13C decreased by 0.5‰ between 2009 and 2013 in soybean cropland, suggesting low OM inputs from soybeans. Together these findings suggest the following: (1) soil C is relatively resistant to changes in land use and (2) conversion to cropland caused a small, measurable reduction in the fast-cycling C pool through reduced OM inputs, mobilization of older C from soil mixing, and/or destabilization of SOM in surface soils.
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ArticleStructure and composition of altered riparian forests in an agricultural Amazonian landscape(Ecological Society of America, 2015-09) Nagy, R. Chelsea ; Porder, Stephen ; Neill, Christopher ; Brando, Paulo ; Quintino, Raimundo Mota ; do Nascimento, Sebastiao AvizDeforestation and fragmentation influence the microclimate, vegetation structure, and composition of remaining patches of tropical forest. In the southern Amazon, at the frontier of cropland expansion, forests are converted and fragmented in a pattern that leaves standing riparian forests whose dimensions are mandated by the Brazilian National Forest Code. These altered riparian forests share many characteristics of well-studied upland forest fragments, but differ because they remain connected to larger areas of forest downstream, and because they may experience wetter soil conditions because reduction of forest cover in the surrounding watershed raises groundwater levels and increases stream runoff. We compared forest regeneration, structure, composition, and diversity in four areas of intact riparian forest and four areas each of narrow, medium, and wide altered riparian forests that have been surrounded by agriculture since the early 1980s. We found that seedling abundance was reduced by as much as 64% and sapling abundance was reduced by as much as 67% in altered compared to intact riparian forests. The most pronounced differences between altered and intact forest occurred near forest edges and within the narrowest sections of altered riparian forests. Woody plant species composition differed and diversity was reduced in altered forests compared to intact riparian forests. However, despite being fragmented for several decades, large woody plant biomass and carbon storage, the number of live or dead large woody plants, mortality rates, and the size distribution of woody plants did not differ significantly between altered and intact riparian forests. Thus, even in these relatively narrow forests with high edge : area ratios, we saw no evidence of the increases in mortality and declines in biomass that have been found in other tropical forest fragment studies. However, because of the changes in both species community and reduced regeneration, it is unclear how long this relative lack of change will be sustained. Additionally, Brazil recently passed a law in their National Forest Code allowing narrower riparian buffers than those studied here in restored areas, which could affect their long-term sustainability.
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ArticleSurprisingly modest water quality impacts from expansion and intensification of large-scale commercial agriculture in the Brazilian Amazon-Cerrado region(Sage, 2017-08-30) Neill, Christopher ; Jankowski, KathiJo ; Brando, Paulo ; Coe, Michael T. ; Deegan, Linda A. ; Macedo, Marcia N. ; Riskin, Shelby H. ; Porder, Stephen ; Elsenbeer, Helmut ; Krusche, Alex V.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.