Project : USDA ARS

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Research Project: Enhancing Water Resources, Production Efficiency and Ecosystem Services in Gulf Atlantic Coastal Plain Agricultural Watersheds

Location: Southeast Watershed Research

2022 Annual Report

Objectives
1. Quantify and assess the interactions among agroecosystems and landscape components and their impacts on water supply and water quality in agricultural watersheds of the southeastern U.S. 2. Quantify and assess the effects of agricultural conservation practices and managed land-use interfaces at field, landscape, and watershed scales in agricultural watersheds of the southeastern U.S. 3. As part of the LTAR network, and in concert with similar long-term, land-based research infrastructure in the Gulf Atlantic Coastal Plain (GACP), use the Little River Experimental Watershed (LREW) LTAR site to improve the observational capabilities and data accessibility of the LTAR network and support research to sustain or enhance agricultural production and environmental quality in agroecosystems characteristic of the Gulf Atlantic Coastal Plain (GACP) region. Research and data collection are planned and implemented based on the LTAR site application and in accordance with the responsibilities outlined in the LTAR Shared Research Strategy, a living document that serves as a roadmap for LTAR implementation. Participation in the LTAR network includes research and data management in support of the ARS GRACEnet and/or Livestock GRACEnet projects. 4. Utilize landscape and watershed scale assessment models to evaluate the long-term sustainability of agricultural watersheds.

Approach
The research integrates field, landscape, and watershed observations. As such, research sites are located at multiple scales each supporting watershed observations. The SEWRL operates watershed facilities Little River Experimental Watershed (LREW) that are the basis for our long-term hydrology and natural resources research. In addition to these watersheds, the SEWRL has established long-term research at plot (~0.2 Ha) and field (> 10 Ha) scales. The objectives in this plan contribute to the LTAR Common Experiment over-arching hypothesis that “aspirational treatments will increase overall carbon stocks and in particular, soil carbon…leading to increased ecosystem resiliency”. Individual sub-objectives are focused on providing an improved understanding of spatial and temporal drivers and ecosystem services responses associated with the three Common Experiment sub-hypotheses: 1) The magnitude, direction and rate of change will vary with topographic and soil characteristics of the landscape; 2) Sustainable ecosystem productivity, yield, and yield quality will be significantly improved by the development of specific and adaptive G x E x M x Social x Economic systems; and 3) Biologically-based inputs will drive the rate and magnitude of carbon stock increases (e.g., nutrient cycling, insect comminution, decomposition, etc.). The experiments presented are designed as an integrated systems approach to understanding processes at the plot-to-landscape scale using the LREW as the synthesis scale for testing and verification of the Long Term Agroecosystem Research Common Experiment hypothesis. Each objective and sub-objective is designed to address selected spatial and temporal scale processes, provide information for qualifying extrapolations between scales, and/or explore novel technical approaches for characterizing ecosystems services within the LREW. We will use remote sensing, geospatial modeling, statistical modeling and process modeling to evaluate linkages and identify information gaps across scales. Specific research will: 1) characterize the impacts that agricultural land management and land-cover have on water resources in southern coastal plain watersheds; 2) examine relationships between conservation practices (including winter cover), indicators of productivity (e.g. SOC, NPP), other drivers of land cover change, and water quality; 3) characterize composition of DOM with land-use; 4) quantify differences between watersheds with agricultural livestock impacts to watersheds with minimal agricultural livestock impact; 5) quantify stream flow and chemistry differences between urbanized and agricultural watersheds; 6) quantify the impact of agricultural irrigation ponds on watershed water balance; 7) quantify differences in provisioning and regulating ecosystem services between typical and aspirational agricultural production systems; 8) compare spatial and temporal variations between provisioning and regulating ecosystems services; and 9) use landscape and watershed scale assessment models to evaluate the long-term sustainability of agricultural watersheds.

Progress Report
This is the final report for the project 6048-13000-027-000D which terminated in February 2022. This project provides supporting information for 6048-13000-028-000D which began in October 2021. Substantial results were realized over the 5 years of the project. Streamflow and water quality data collected at multiple scales provided insight into relationships between agricultural management and hydrologic processes. Geographical Information System (GIS) databases of soils, hydrography, land-cover, and land-management across the LREW were established to support the analysis. These were the basis for geospatial research relating large scale processes to watershed characteristics. This work is fundamental to the NRCS Conservation Effects Assessment Project (CEAP). New research related land-use to dissolved organic matter (DOM). Eddy covariance data were collected at two sites for quantifying the exchange rates of trace gases over agricultural ecosystems. Carbon and water budgets established by this research are critical for quantifying agriculture’s role in climate change. Very high resolution RGB, multispectral imagery and thermal data from a small unmanned aircraft system (sUAS) were gathered to scale yield measurements from field to landscape. New research on a bioenergy feedstock, Miscanthus x giganteus, related high precision measurements of plant health and field characteristics, such as soil and aspect, with the presence of phloem-feeding insects and their natural predators over the course of the season. Watershed scale assessment models were used to evaluate the long-term sustainability of agricultural watersheds in the coastal plain of Georgia. Specifically, we quantified the impacts of conservation practices and winter covers in the LREW. Regional assessments of ecosystem services in the southeast showed how tradeoffs among ecosystem services vary across the region. This work underscored the findings that riparian buffers and conservation practices provide important regulating services in watersheds of the LREW, and southeast in general, and play a fundamental role in the CEAP project.

Accomplishments
1. Validation of Remotely Sensed Soil-Water. Estimates of soil moisture across the globe are critical for prediction of climate, water balance, and crop production. Soil moisture is fundamental to agricultural management and provides critical information on hydrologic and climatic processes. The Little River Experimental Watershed (LREW) managed by ARS researchers in Tifton, Georgia, is part of a nation-wide network of core validation sites collecting continuous in-situ soil-water across large spatial areas. This network has played a crucial role in the calibration and validation of satellite based remotely sensed soil-water. Tremendous improvements have been made in accuracy and resolution of these remotely sensed data, documented through 34 scientific publications utilizing data collected at the LREW and other locations within the core validation network. The credibility of the remotely sensed data has been greatly enhanced by the testing provided by this nationwide in-situ network. The LREW provides a unique data set for the diverse Coastal Plain landscape.

2. Importance of Long-term data in understanding soil moisture. Soil moisture is fundamental to agricultural management and provides critical information on hydrologic and climatic processes. The validation of national and global soil moisture utilizing data collected from satellites and simulated by numerical models uses ground-based measurements for verification purposes. The ground-based measurements are often assumed stable over time, but there has been little research demonstrating the consistency of a data and their variability over time. A nationwide study including ARS researchers in Tifton, Georgia, and from several other ARS watershed locations, found that ground-based measurements were able to adequately capture a full range of soil moisture conditions within one calendar year. The incorporation of long-term soil moisture data is helping to improve national and global models of soil moisture dynamics, including drought impacts, and is encouraging for network scaling activities and validation campaigns.

3. Little River Watershed at Tifton, Georgia, a testbed for the ARS National Ecosystems Model (NAM). Although the Soil Water Assessment Tool (SWAT) model is commonly used to predict the impacts of agricultural practices on water quality and quantity, the data framework that drives SWAT in the U.S. is fragmented and inconsistent, varying by user and model interface. The NAM model provides a unified field to-national scale modeling framework with sufficient detail to capture field-level processes and management actions spanning the full extent of the contiguous U.S. This model is fundamental for making large scale agri-management decisions across the U.S. The NAM was tested in a case study of the Little River Watershed by ARS researchers in Tifton, Georgia. Test results indicate the model can be used to produce reliable estimates of the impact of conservation alternatives for the Southeastern U.S.

4. Simplifying hydroclimate risk planning. Categorizing regions of the world according to climate and water interactions is valuable for assessing the effects that too much or too little water has on multiple societal systems such as food production, flood control, road and bridge design, and economic development. Existing climate classification systems are complex, require large amounts of data, and often do not correctly capture areas that respond similarly to changes in how precipitation extremes affect water scarcity and flood risk. ARS researchers in Tifton, Georgia, and the University of Florida developed the Water-Energy Clustering Classification (WEC) system that requires less data than existing systems and better characterizes water availability. The WEC system can serve as an effective and easy to use tool to estimate risk associated with weather extremes and to set criteria for estimating costs of prevention and mitigation.

5. Multi-species biodiversity assessment under pine plantation biofuel management strategies. Increased demand for sustainable energy feedstock production has the potential to drive agricultural land use changes that would have unknown impacts on biodiversity. ARS researchers in Tifton, Georgia, worked in partnership with a team led by the University of Florida to evaluate the impact of three pine plantation management strategies (thinning, short-rotation, and clear-cut) on the biodiversity of bats, bees, birds, and reptiles at multiple sites within the southeastern United States. The biodiversity of all groups was lower under short-rotation and clear-cut conditions but increased under pine thinning. Beta-diversity, a measure of how species composition differs across sites, was also observed to provide a clearer picture of differences among habitats occupied by the four species groups under each management strategy. The results suggest that landowners may be able to increase local biodiversity by thinning pine plantations and that beta-diversity may be a useful tool for incorporating biodiversity goals into regional landscape management plans.

6. The science, ecological effects, and management of rural road networks. Rural roads comprise the bulk of the global road network, even in highly industrialized countries. These roads provide critical linkages for rural communities. However, roads and their traffic also have negative ecological impacts on the rural landscapes where they exist, including water and air pollution, soil erosion, and effects on wild animal and plant populations. While the general ecological effects of highways has been well studied, a comprehensive understanding of the problems cause specifically by rural roads was not clear. This work, led by ARS researchers in Tifton, Georgia, combined the expertise of notable road ecology scientists from other US Government agencies, academic, and non-profit researchers from Europe and North America. The work describes, in “layman’s terms”, the state of road ecology science focused on rural roads and includes valuable guidance on “best practices” for planning, constructing, and maintaining rural road networks. This compilation of information about rural road networks in one place provided a novel perspective for ecologists and transportation and land managers alike. The publication from this collaboration was published in both English and Spanish and is freely available from the Ecological Society of America, making it widely available to rural land managers in English and Spanish speaking regions of the world.

U.S. DEPARTMENT OF AGRICULTURE

Southeast Watershed Research: Tifton, GA