Scaling of Watershed Functional Trait Co-variability
Authors
Evan King1*, Haruko M. Wainwright1, 2, Michelle Newcomer2, Lijing Wang2, Nicola Falco2, Eoin L. Brodie2 (elbrodie@lbl.gov)
Institutions
1Massachusetts Institute of Technology, Cambridge, MA; 2Lawrence Berkeley National Laboratory, Berkeley, CA
Abstract
Key to understanding watershed functions is characterizing aboveground (e.g., vegetation dynamics, topography) and belowground (e.g., soil and bedrock structures) properties, which in turn govern patterns of important hydro-biogeochemical processes. These important properties are defined as watershed functional traits: properties whose coevolution and resulting covariance and interactions regulate the behavior of a watershed. However, it is challenging to capture these traits on the watershed scale, often due to their high heterogeneity. Partitioning watersheds into a series of hillslopes offers both the opportunity to narrow these heterogeneities and to examine co-variability across above- and belowground traits. The team utilized two adjacent Colorado watersheds, the East River and Taylor River, which display a diverse set of bedrock-through-canopy characteristics, such as geology, vegetation coverage, and snow coverage. Using topography, researchers delineated watersheds into appropriate hillslope units based on multiple threshold drainage areas and determined key hillslope metrics from geospatial layers.
Specifically, the team investigated the relationship between plant species distribution, subsurface structure, and hillslope geometry. By varying threshold drainage area, researchers investigated the scaling relationships between hillslope size, trait co-variability, and the ability to capture watershed-wide variability in these metrics. Results showed that across both watersheds, hillslope-averages of slope and elevation are significantly correlated and that conifer-dominated hillslopes are primarily located in mid-slope, mid-elevation, and granitic rock regions. The diversity of geology in the East River watershed might be associated with mixed vegetation types.