W1007: Benchmark soilscapes to predict effects of climatic change in the western USA
Statement of Issues and JustificationThe effects of climate change on soils are not well known, although it is widely recognized that soil properties vary greatly and function differently as a result of the climate conditions in which they are found. Global circulation models predict a 3 to 4 °F increase in temperatures by 2030 and 8 to 11°F by 2090 for the western US. Predictions of precipitation are less conclusive. Two climate model scenarios forecast an increase in precipitation, particularly in California, and a drying in parts of the Rocky Mountains, while others predict drier conditions in the Rocky Mountains by 2030 (NAST, 2001). Crucial unknowns identified by the US Global Change Research Program suggest that comprehensive studies are needed to document interactions between soils, water, and air resources.
Soils are the foundation of a myriad of ecosystem processes and services on the planet, yet few studies have addressed the soils greater role interacting with the atmosphere, hydrosphere, lithosphere and biosphere (Rosenzweig and Hillel, 2000). Examples of ecosystem services soils provide include air and water purification, stabilization against erosion, flood control, carbon storage and regulation of nutrient and water supply. Understanding the ecosystem services soils provide in the context of climate change is imperative for planning and policy development by stakeholders in agriculture and natural resources. Our goal is to investigate the resiliency of soils (and near surface processes regulated by soil) to climate change in a manner that meets the needs of the National Cooperative Soil Survey (NCSS), while addressing critical natural resource issues in the western U.S. The National Cooperative Soil Survey (NCSS) is a nationwide partnership of federal, regional, state and local agencies; and private entities and institutions. This partnership (including the State Agricultural Experiment Stations) works together to cooperatively investigate, inventory, document, classify, interpret, disseminate, and publish information about soils of the United States and its trust territories and commonwealths. The activities of the NCSS are carried out on national, regional, and state levels. Primary federal agency NCSS participants include Bureau of Indian Affairs (BIA), Bureau of Land Management (BLM), Department of Defense (DoD), Forest Service (FS), National Park Service (NPS), and Natural Resources Conservation Service (NRCS). Than National Soil Survey Handbook can be found at the following URL: http://www.soils.usda.gov/technical/handbook/
Pedologists of the western region have recognized the need for a regional understanding of the effects of global warming on soil change. To predict the impacts of climate change we will establish a framework of benchmark soilscapes as monitoring sites across the western U.S. in the form of two regional bioclimatic sequences, one established in transported materials and the other in residuum. In these sequences the variation among soil forming factors, parent material, age, and relief will be minimized to study the effects of climate and vegetation on soil properties. The project will emphasize changes in physical, chemical, mineralogical, hydrological and morphological characteristics of benchmark soilscapes that are tied to pedologic processes. These data will be used to illustrate and predict soil properties and processes as a function of climate. This infrastructure will also serve as pilot landscapes to explore the ability of soil survey to address soil change over human timescales.
Improving the benchmark soil list is a national priority for the NCSS because it offers the opportunity to apply research to representative soils that occupy dominant positions in a region. The NCSS recognizes benchmark soils as geographically important soils that occupy the greatest spatial extent of a soil survey area or have regional land-use importance. Currently, there are significant gaps in the NCSS benchmark soils dataset and the variability of soil properties within these soilscapes is unknown. We see an opportunity to expand upon the importance of these landscapes by demonstrating how soil properties and near-surface processes evolve and change in response to climate. Our approach will be to establish long-term research sites across carefully selected elevation gradients to form soil developmental sequences within 5-10 representative biogeographic provinces of the western US, that when combined in a multistate research effort, form one of two regional bioclimatic sequences. By examining how soil properties in these benchmark soils respond to climate, we propose to develop conceptual and empirical models to predict changes in soil and near surface processes under future climate change scenarios (Fig. 1a)(See Attachments). This same approach will be used to identify pedogenic thresholds that buffer the ecosystem from change and yet facilitate rapid change when overwhelmed (Fig. 1b; Chadwick and Chorover, 2001).
We hypothesize that climate change impacts on the western U.S. can be determined by quantifying temperature and precipitation, the two main climatic drivers of soil formation, and soil forming processes, across the regional soil bioclimatic gradient. This study will focus on four major soil forming processes: 1) primary mineral weathering and secondary mineral formation, 2) organic matter accumulation, 3) leaching and 4) organism effects on soil. These four processes result in observable soil morphologic features (e.g., color, texture, soil mineralogy, structure, and horizonation) that indicate the soil physical, chemical and biological properties involved in ecosystem function. This study will document the linkages between soil forming processes, soil morphology, and important ecosystem services such as phosphorus cycling, carbon sequestration, biodiversity and regulating quantity and quality of water. The timescales over which these processes occur vary, from human timescales (decades) to geologic time (thousands to millions of years). In this study, soil morphologic properties will be used to reflect the effects of climate over geologic time, and related dynamic soil properties, such as aggregate stability, infiltration rate, consistence, and surface soil strength will be used to document soil change over human timescales.
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