Do mitigation strategies reduce global warming potential in the northern U.S. corn belt?

Agricultural management practices that enhance C sequestration, reduce greenhouse gas emission (nitrous oxide [N?O], methane [CH?], and carbon dioxide [CO?]), and promote productivity are needed to mitigate global warming without sacrificing food production. The objectives of the study were to compare productivity, greenhouse gas emission, and change in soil C over time and to assess whether global warming potential and global warming potential per unit biomass produced were reduced through combined mitigation strategies when implemented in the northern U.S. Corn Belt. The systems compared were (i) business as usual (BAU); (ii) maximum C sequestration (MAXC); and (iii) optimum greenhouse gas benefit (OGGB). Biomass production, greenhouse gas flux change in total and organic soil C, and global warming potential were compared among the three systems. Soil organic C accumulated only in the surface 0 to 5 cm. Three-year average emission of N?O and CH was similar among all management systems. When integrated from planting to planting, N?O emission was similar for MAXC and OGGB systems, although only MAXC was fertilized. Overall, the three systems had similar global warming potential based on 4-yr changes in soil organic C, but average rotation biomass was less in the OGGB systems. Global warming potential per dry crop yield was the least for the MAXC system and the most for OGGB system. This suggests management practices designed to reduce global warming potential can be achieved without a loss of productivity. For example, MAXC systems over time may provide sufficient soil C sequestration to offset associated greenhouse gas emission.     

Dynamic floodplain vegetation model development for the Kootenai River, USA

The Kootenai River floodplain in Idaho, USA, is nearly disconnected from its main channel due to levee construction and the operation of Libby Dam since 1972. The decreases in flood frequency and magnitude combined with the river modification have changed the physical processes and the dynamics of floodplain vegetation. This research describes the concept, methodologies and simulated results of the rule-based dynamic floodplain vegetation model "CASiMiR-vegetation" that is used to simulate the effect of hydrological alteration on vegetation dynamics. The vegetation dynamics are simulated based on existing theory but adapted to observed field data on the Kootenai River. The model simulates the changing vegetation patterns on an annual basis from an initial condition based on spatially distributed physical parameters such as shear stress, flood duration and height-over-base flow level. The model was calibrated and the robustness of the model was analyzed. The hydrodynamic (HD) models were used to simulate relevant physical processes representing historic, pre-dam, and post-dam conditions from different representative hydrographs. The general concept of the vegetation model is that a vegetation community will be recycled if the magnitude of a relevant physical parameter is greater than the threshold value for specific vegetation; otherwise, succession will take place toward maturation stage. The overall accuracy and agreement Kappa between simulated and field observed maps were low considering individual vegetation types in both calibration and validation areas. Overall accuracy (42% and 58%) and agreement between maps (0.18 and 0.27) increased notably when individual vegetation types were merged into vegetation phases in both calibration and validation areas, respectively. The area balance approach was used to analyze the proportion of area occupied by different vegetation phases in the simulated and observed map. The result showed the impact of the river modification and hydrological alteration on the floodplain vegetation. The spatially distributed vegetation model developed in this study is a step forward in modeling riparian vegetation succession and can be used for operational loss assessment, and river and floodplain restoration projects.     

Denitrification mitigates N flux through the stream-floodplain complex of a desert city

The Indian Bend Wash (IBW) flood-control project relies on a greenbelt to carry floods through Scottsdale, Arizona, USA. The greenbelt is characterized by a chain of shallow artificial lakes in a larger floodplain of irrigated turf, which has been protected from encroaching urban development. As such, this urban stream-floodplain complex can be divided into three subsystems: artificial lakes, channelized stream segments, and floodplain. We conducted experiments to evaluate which, if any, of these subsystems were important sites of denitrification, and to explore factors controlling denitrification rates. Denitrification enzyme activity (DEA) bioassays were conducted on sediments from eight lake and six stream segments as well as soil samples from eight floodplain transects. Mass-specific potential denitrification rates were significantly higher in lakes than in streams or floodplains. Nutrient limitation bioassays revealed that nitrate (NO3-) limited denitrification in lake sediments, a surprising finding given that NO3(-)-rich groundwater additions frequently raised lake NO3(-) concentration above 1 mg N/L. Experiments on intact lake cores suggested that denitrification was limited by the rate NO3(-) diffused into sediments, rather than its availability in overlying water. Floodplain denitrification was limited by water content, not NO3(-) or C, and irrigation of soils stimulated denitrification. We constructed a N budget for the IBW stream-floodplain complex based on our experimental results. We found that both lakes and floodplains removed large quantities of N, with denitrification removing 261 and 133 kg N ha(-1) yr(-1) from lake sediments and floodplain soils, respectively, indicating that lakes are hotspots for denitrification. Nevertheless, because floodplain area was >4.5 times that of lakes, floodplain soils removed nearly 2.5 times as much N as lake sediments. Given the desert's low annual precipitation, a finding that floodplain soils are active sites of denitrification might seem implausible; however, irrigation is common in urban landscapes, and it elevated annual denitrification in IBW. Based on our results, we conclude that construction of artificial lakes created hotspots while application of irrigation water created hot moments for denitrification in the stream-floodplain complex, demonstrating that management decisions can improve the ability of urban streams to provide critical ecosystem services like N retention.     

Nitrogen and phosphorus budgets for the Yucat��n littoral: An approach for groundwater management

Human activities have altered the balance of ecosystems to the detriment of natural environments. Eutrophication is a serious risk in Yucatán, a state in the eastern peninsula of México where groundwater supplies the only freshwater to a karst shelf environment. While economic development in Yucatán is increasing, environmental awareness is lagging, and efficient waste treatment systems are lacking. To assess potential nitrogen and phosphorus inputs into the coastal zone of Yucatán, we analyzed government reports and the chemical composition of groundwater and aquaculture wastewater. Swine, poultry, and tourism are revealed as the main continental nutrient sources, while groundwater with high nitrate concentrations is the principal coastal nutrient source, a pattern similar to other river discharges around the world. This study demonstrates that environmental risk management practices must be implemented in the Yucatán region to protect groundwater quality.     

Mercury and selenium concentrations in the crab Callinectes arcuatus from three coastal lagoons of NW Mexico

Environmental Science and Pollution Research - Mercury and selenium concentrations and Se:Hg molar ratio in edible muscle and hepatopancreas of the crab Callinectes arcuatus from coastal lagoons of...     

Species-specific bioluminescence facilitates speciation in the deep sea

The vast darkness of the deep sea is an environment with few obvious genetic isolating barriers, and little is known regarding the macroevolutionary processes that have shaped present-day biodiversity in this habitat. Bioluminescence, the production and emission of light from a living organism through a chemical reaction, is thought to occur in approximately 80 % of the eukaryotic life that inhabits the deep sea (water depth greater than 200 m). In this study, we show, for the first time, that deep-sea fishes that possess species-specific bioluminescent structures (e.g., lanternfishes, dragonfishes) are diversifying into new species at a more rapid rate than deep-sea fishes that utilize bioluminescence in ways that would not promote isolation of populations (e.g., camouflage, predation). This work adds to our understanding of how life thrives and evolution shaped present-day biodiversity in the deep sea, the largest and arguably least explored habitat on earth.     

Modeling regional impacts of climate teleconnections using functional data analysis

Teleconnections are quasi-periodic changes in atmospheric circulation that oscillate over long periods of time and impact climate over large regions. These patterns are often linked to long-term variations in climate and extreme weather events and may explain regional differences in climate vulnerability. We apply methods of functional data analysis to examine regional impacts of teleconnections on climate in British Columbia, Canada, between 1951 and 2000. We focus on monthly mean temperature as an overall determinant of crop growth and apply functional principal components analysis (FPCA) to study variations in the impacts of four major teleconnection indices affecting the Northern Hemisphere (the Southern Oscillation Index, the Pacific North American (PNA), Pacific Decadal Oscillation, and the North American Oscillation indices). Two challenges we consider are that the impacts of teleconnections cannot be observed directly and that fine scale data required to study regional variations may come from different sources with highly varied records. We first fit thin-plate regression splines to the raw data to construct complete series of pseudo-data at fixed grid points. Regression models incorporating Bayesian P-splines were then fit to the pseudo-data to estimate the impacts of the four teleconnections over time. Finally, FPCA was then applied to study regional variations in these effects. Our analysis identified strong variations in mean temperature associated with the PNA. The resulting spatial patterns also reveal areas of increased/decreased temperature variability that may have higher climate risk or be suitable for expansion of agricultural activity.     

Usefulness of natural regions for lake management: Analysis of variation among lakes in northwestern Wisconsin,USA

A map of summer total phosphorus in lakes was compiled recently for a three-state area of the upper Midwest for purposes of identifying regional patterns of total phosphorus in lakes and attainable lake trophic state. Spatial patterns in total phosphorus from approximately 3000 lakes were studied in conjunction with maps of geographic characteristics that tend to affect phosphorus balance in lakes to identify regions of similarity in phosphorus concentrations in lakes or similarity in the mosaic of values as compared to adjacent areas. While degrees of relative homogeneity are apparent at many scales, the map was designed at a scale that would yield regions with sufficient homogeneity to be useful for lake management throughout the area. In this study, data from 210 lakes in a 1560-mi² area in northwestern Wisconsin, sampled by the Wisconsin Department of Natural Resources in the spring of 1988 (subsequent to the compilation of the phosphorus map), were examined to: (1) substantiate the existence of the regions depicted on the map in northwest Wisconsin, (2) determine the nature and relative precision of the regional boundaries, (3) determine the relative importance of natural and anthropogenic watershed characteristics, lake types, lake area, and lake depth in explaining within-region differences in lake phosphorus, and (4) demonstrate how the regions might be used by local lake managers.