|JI, WENJIE - New Mexico State University
|HANAN, NIALL - New Mexico State University
|MONGER, H. CURTIS - Natural Resources Conservation Service (NRCS, USDA)
|ARCHER, STEVE - University Of Arizona
|ROSS, C. WADE - New Mexico State University
|LIND, BRIANNA - New Mexico State University
|ANCHANG, JULIUS - New Mexico State University
|KUMAR, SANATH - New Mexico State University
|PRIHODKO, LARA - New Mexico State University
Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2018
Publication Date: 2/1/2019
Citation: Ji, W., Hanan, N., Browning, D.M., Monger, H., Peters, D.C., Bestelmeyer, B.T., Archer, S.R., Ross, C., Lind, B.M., Anchang, J., Kumar, S., Prihodko, L. 2019. Constraints on shrub cover and shrub-shrub competition in a U.S. southwest desert. Ecosphere. 10(2):e02590. https://doi.org/10.1002/ecs2.2590.
Interpretive Summary: The transition from grass- to shrub-domination is widely observed in the world’s rangeland ecosystems. These transitions hold important ramifications for land use, sustainability of livestock production, and ecosystem services such as clean water, human health, and recreation. We examined water holding capacity and shrub-shrub interactions as limitations on the proliferation of shrubs. We used mapping methods applied to 2011 aerial photography and spatially-explicit soils information to identify that soil properties interact with biotic interactions to determine the upper limit on shrub cover. This study brought together information on soils, remote sensing, field methods, and ecology to assess the robustness of published models that predict maximum shrub cover. Our findings can benefit state and federal land managers and decision makers charged with efficient allocation of resources for management activities such as grassland remediation, as well as ecologists and soil scientists involved in ecological state mapping.
Technical Abstract: The cover of woody perennial plants (trees and shrubs) in arid ecosystems is at least partially constrained by water availability. However, the extent to which maximum canopy cover is limited by rainfall, and the degree to which soil water holding capacity and topography impacts maximum shrub cover are not well understood. Similar to many other deserts in the U.S. southwest, plant communities at the Jornada Basin Long-Term Ecological Research (LTER) site in the northern Chihuahuan Desert have experienced a long-term state-change from perennial grassland to shrubland dominated by woody plants. To better understand this transformation, and the environmental controls and constraints on shrub cover, we created a shrub cover map using high spatial resolution images and explored how maximum shrub cover varies with landform, water availability, and soil characteristics. Our results indicate that when clay content is below ~18%, the upper limit of shrub cover is positively correlated with plant available water as mediated by surface soil clay influence on water retention. At surface soil clay contents >18%, maximum shrub cover decreases, presumably because the amount of water percolating to depths preferentially used by deep-rooted shrubs is diminished. In addition, the relationship between shrub cover and density suggests that self-thinning occurs in denser stands in most landforms of the Jornada Basin, indicating that shrub-shrub competition interacts with soil properties to constrain maximum shrub cover in the northern Chihuahuan Desert.