Soil characteristics are associated with gradients of big sagebrush canopy structure after disturbance

Authors: Barnard, David; GERMINO, M - Us Geological Survey (USGS); ARKLE, R - Us Geological Survey (USGS); BRADFORD, J - Us Geological Survey (USGS); DUNIWAY, M - Us Geological Survey (USGS); PILLIOD, D - Us Geological Survey (USGS); PYKE, D - Us Geological Survey (USGS); SHRIVER, R - Us Geological Survey (USGS); WELTY, J - Us Geological Survey (USGS)

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2019
Publication Date: 6/11/2019
Citation: Barnard, D.M., Germino, M.J., Arkle, R.S., Bradford, J.B., Duniway, M.C., Pilliod, D.S., Pyke, D.A., Shriver, R.K., Welty, J.L. 2019. Soil characteristics are associated with gradients of big sagebrush canopy structure after disturbance. Ecosphere. 10(6):1-12. https://doi.org/10.1002/ecs2.2780.
DOI: https://doi.org/10.1002/ecs2.2780

Interpretive Summary: In the Great Basin, USA, reestablishing sagebrush canopy cover after fire is important for restoring ecosystem functioning and providing shelter and forage for wildlife. Much research has focused on landscape factors affecting success or failure of sagebrush restoration treatments, but few have focused solely on easily measure soil characteristics associated with gradients in sagebrush canopy recovery in successfully reestablished populations. In this study, we analyzed measurements of sagebrush canopy structure (in terms of canopy height, cover, and plant density) in relation to soil texture, surface condition, and biological crust formation. Sagebrush plant density and canopy cover were generally greater in areas with deeper and sandier-textured soils, whereas canopy height was generally greater in areas with finer-texture soils, and the presence of biological crusts were positively associated with greater sagebrush canopy recovery overall. We found these soil associations to be more explanatory of sagebrush canopy recovery than climate variation among sites. The relationships we characterize in this study will be of great use to resource managers across the western United States as they increasingly prioritize focused restoration treatments into areas with the greatest chances of recovery.

Technical Abstract: Reestablishing shrub canopy cover after disturbance in semi-arid ecosystems, such as sagebrush steppe, is essential to provide wildlife habitat and restore ecosystem functioning. While several studies have explored the effects of landscape and climate factors on the success or failure of sagebrush seeding, the influence of soil properties on gradients of shrub canopy structure in successfully seeded areas remains largely unexplored. In this study, we evaluated associations between soil properties and gradients in sagebrush canopy structure in stands that had successfully reestablished after fire and subsequent seeding treatments. Using a dataset collected across the Great Basin, USA of sagebrush stands that had burned and reestablished between 1986 and 2013, we tested soil depth and texture, soil surface classification, biological soil crusts plus mean historical precipitation, solar heatload, and fire history, as modeling variables to explore gradients in sagebrush canopy structure growth in terms of cover, height, and density. Deeper soils were associated with greater sagebrush canopy structure development in terms of plant density and percent cover, coarser textured soils were associated with greater sagebrush cover and density, and more clayey soils were typically associated with greater height. Biological crust presence was also positively associated with enhanced sagebrush canopy growth, but adding more demographically or morphologically explicit descriptions of biocrust communities did not improve explanatory power. Increasing heatload had a negative effect on sagebrush canopy structure growth and increased mean annual precipitation was only associated with greater sagebrush height. Given that conservation and restoration of the sagebrush steppe ecosystems has become a priority for land managers, the associations we identify between gradients in post-fire sagebrush canopy structure growth and field identifiable soil characteristics may improve planning of land treatments for sagebrush restoration and the understanding of semi-arid ecosystem functioning and post-disturbance dynamics.