Nutrient export to groundwater across a land use and historical climate gradient

Groundwater inputs to streams are important to intermittent stream function and can be a source of nutrients such as nitrogen and phosphorus. The amount of nutrients within groundwater are an important factor for downstream processes, including eutrophication far from the groundwater source. We asked whether land use and precipitation affect nutrient export patterns to groundwater. Soil samples were taken from sites across a variable precipitation gradient in Kansas with three land uses: agriculture, native prairie, and restored prairie. By analyzing the relative concentrations of nitrogen and phosphorus in the water after leaching the soil samples in mesocosms, we can tell how water quality is affected by land use and precipitation patterns, especially in intermittent streams

Seasonal Salinization Decreases Spatial Heterogeneity of Sulfate Reducing Activity

This work is licensed under a Creative Commons Attribution 4.0 International License.Evidence of sulfate input and reduction in coastal freshwater wetlands is often visible in the black iron monosulfide (FeS) complexes that form in iron rich reducing sediments. Using a modified Indicator of Reduction in Soils (IRIS) method, digital imaging, and geostatistics, we examine controls on the spatial properties of FeS in a coastal wetland fresh-to-brackish transition zone over a multi-month, drought-induced saltwater incursion event. PVC sheets (10 × 15 cm) were painted with an iron oxide paint and incubated vertically belowground and flush with the surface for 24 h along a salt-influenced to freshwater wetland transect in coastal North Carolina, USA. Along with collection of complementary water and soil chemistry data, the size and location of the FeS compounds on the plate were photographed and geostatistical techniques were employed to characterize FeS formation on the square cm scale. Herein, we describe how the saltwater incursion front is associated with increased sulfate loading and decreased aqueous Fe(II) content. This accompanies an increased number of individual FeS complexes that were more uniformly distributed as reflected in a lower Magnitude of Spatial Heterogeneity at all sites except furthest downstream. Future work should focus on streamlining the plate analysis procedure as well as developing a more robust statistical based approach to determine sulfide concentration

Variation in Stream Chemistry Across the Kansas Precipitation Gradient

How do stream order, land use, and stream position within the precipitation gradient across Kansas affect stream chemistry? Land use will drive changes in stream chemistry that are biologically driven (e.g., DOC, NO3-), whereas stream order or position in the precipitation gradient will have a greater affect on conservative (e.g., Cl- or Na+). Take home message is stream order was the most consistent factor for explaining variation in stream chemistry. Land use never explained the highest amount of variation in stream chemistry. Stream chemistry did not vary between Central and Eastern Kansas streams

Spatiotemporal predictions of soil properties and states in variably saturated landscapes

Understanding greenhouse gas (GHG) fluxes from landscapes with variably saturated soil conditions is challenging given the highly dynamic nature of GHG fluxes in both space and time, dubbed hot spots, and hot moments. On one hand, our ability to directly monitor these processes is limited by sparse in situ and surface chamber observational networks. On the other hand, remote sensing approaches provide spatial data sets but are limited by infrequent imaging over time. We use a robust statistical framework to merge sparse sensor network observations with reconnaissance style hydrogeophysical mapping at a well‐characterized site in Ohio. We find that combining time‐lapse electromagnetic induction surveys with empirical orthogonal functions provides additional environmental covariates related to soil properties and states at high spatial resolutions (~5 m). A cross‐validation experiment using eight different spatial interpolation methods versus 120 in situ soil cores indicated an ~30% reduction in root‐mean‐square error for soil properties (clay weight percent and total soil carbon weight percent) using hydrogeophysical derived environmental covariates with regression kriging. In addition, the hydrogeophysical derived environmental covariates were found to be good predictors of soil states (soil temperature, soil water content, and soil oxygen). The presented framework allows for temporal gap filling of individual sensor data sets as well as provides flexible geometric interpolation to complex areas/volumes. We anticipate that the framework, with its flexible temporal and spatial monitoring options, will be useful in designing future monitoring networks as well as support the next generation of hyper‐resolution hydrologic and biogeochemical models

Weather whiplash in agricultural regions drives deterioration of water quality

Excess nitrogen (N) impairs inland water quality and creates hypoxia in coastal ecosystems. Agriculture is the primary source of N; agricultural management and hydrology together control aquatic ecosystem N loading. Future N loading will be determined by how agriculture and hydrology intersect with climate change, yet the interactions between changing climate and water quality remain poorly understood. Here, we show that changing precipitation patterns, resulting from climate change, interact with agricultural land use to deteriorate water quality. We focus on the 2012â2013 Midwestern U.S. drought as a ânatural experimentâ. The transition from drought conditions in 2012 to a wet spring in 2013 was abrupt; the media dubbed this âweather whiplashâ. We use recent (2010â2015) and historical data (1950â2015) to connect weather whiplash (drought-to-flood transitions) to increases in riverine N loads and concentrations. The drought likely created highly N-enriched soils; this excess N mobilized during heavy spring rains (2013), resulting in a 34% increase (10.5 vs. 7.8 mg N Lâ»Â¹) in the flow-weighted mean annual nitrate concentration compared to recent years. Furthermore, we show that climate change will likely intensify weather whiplash. Increased weather whiplash will, in part, increase the frequency of riverine N exceeding E.P.A. drinking water standards. Thus, our observations suggest increased climatic variation will amplify negative tren

The role of interface organizations in science communication and understanding

“Interface” organizations are groups created to foster the use of science in environmental policy, management, and education. Here we compare interface organizations that differ in spatial scale, modes of operation, and intended audience to illustrate their diversity and importance in promoting the application of science to environmental issues. There has been exciting recent growth in the nature and extent of activities by interface organizations and in new methods for science communication and engagement. These developments can help scientists – who face personal and institutional challenges when attempting to convey the results of their research to various audiences – interact with society on specific issues in specific places, and with a wide range of non-traditional audiences. The ongoing mission for these organizations should be to move beyond simply increasing awareness of environmental problems to the creation of solutions that result in genuine environmental improvements

Synchrony of net nitrogen mineralization and maize nitrogen uptake following applications of composted and fresh swine manure in the Midwest U.S.

Understanding how the quality of organic soil amendments affects the synchrony of nitrogen (N) mineralization and plant N uptake is critical for optimal agronomic N management and environmental protection. Composting solid livestock manures prior to soil application has been promoted to increase N synchrony; however, few field tests of this concept have been documented. Two years of replicated field trials were conducted near Boone, Iowa to determine the effect of composted versus fresh solid swine manure (a mixture of crop residue and swine urine and feces produced in hoop structures) on Zea mays (maize) N uptake, in situ soil net N mineralization, and soil inorganic N dynamics. Soil applications of composted manure increased maize N accumulation by 25 % in 2000 and 21 % in 2001 compared with fresh manure applications (application rate of 340 kg N ha-1). Despite significant differences in net N mineralization between years, within year seasonal total in situ net N mineralization was similar for composted and fresh manure applications. Partial N budgets indicated that changes in soil N pools (net N mineralization and soil inorganic N) in the surface 20 cm accounted for 67 % of the total plant N accumulation in 2000 but only 16 % in 2001. Interannual variation in maize N accumulation could not be attributed to soil N availability. Overall, our results suggest that composting manures prior to soil application has no clear benefit for N synchrony in maize crops. Further work is required to determine the biotic and abiotic factors underlying this result