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Tuesday, April 10 • 10:00am - 10:15am
BELOWGROUND PROCESSES: Understanding Spatial Soil Moisture as a Driver of Ecohydrological Processes: Does One Relationship Rule Them All?

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AUTHORS: Charles I. Scaife, University of Virginia; Jonathan Duncan, Pennsylvania State University; Naomi Tague, University of California-Santa Barbara; Colin Bell, Colorado School of MINES; Lawrence Band, University of Virginia

ABSTRACT: Soil moisture extremes drive ecohydrological processes, but the spatially variable nature of soil moisture makes characterizing patterns across the landscape particularly challenging. A consensus among the literature is that spatial variance is lowest at both high and low mean soil moisture values forming concave mean-variance relationships. Topography has previously served as a template for landscape-level patterns of mean soil moisture and variance, particularly in hydrologically-focused research. However, nitrogen cycling studies are, to a greater degree, concerned with spatial variation of soil moisture as it relates to biogeochemical cycling at ecological patch scales or smaller. Non-linear relationships describing nutrient dynamics require consideration of small-scale heterogeneity not captured in landscape-scale studies. We’ve previously shown at a single-site that including spatial variance reduces bias in nutrient cycling estimates. In this study, we reconcile scale discrepancies by posing a simple question: how similar are patterns of plot-scale soil moisture measurements between sites representing a variety of land-uses and vegetation cover? Our analysis combines over 8000 point measurements and 6 years of data across 8 sites encompassing dry and wet years to answer this question. Our goal is to utilize point-based measurements from other studies to broadly characterize plot-scale mean-variance relationships. Preliminary results suggest that despite differences in vegetation and land-use there is agreement between mean-variance relationships across sites in the mid-Atlantic. Differences between landscape positions within a single site (i.e. riparian versus upslope) are greater than differences between sites. While our study focuses primarily on the mid-Atlantic region, similar mean-variance relationships may exist in other regions. Ultimately, these uniquely-defined relationships can provide a useful framework for future integration into hydroecological models where soil moisture modelling is often done at coarser resolutions. Improved downscaling of spatial soil moisture in empirical studies and within these models can further enhance our estimates of nitrification and denitrification rates.

Tuesday April 10, 2018 10:00am - 10:15am CDT
LaSalle 2 (7th Floor)