How will climate change impact woody plant encroachment and how will the effectiveness of current efforts to manage woody encroachment change?

Authors: Bestelmeyer, Brandon; TWIDWELL, DIRAC - University Of Nebraska

Submitted to: Society of Range Management
Publication Type: Abstract Only
Publication Acceptance Date: 12/1/2023
Publication Date: 2/29/2024
Citation: Bestelmeyer, B.T., Twidwell, D. 2024. How will climate change impact woody plant encroachment and how will the effectiveness of current efforts to manage woody encroachment change?. Society of Range Management. Abstract.

Interpretive Summary:

Technical Abstract: Woody plant encroachment is a global problem and woody plant cover is increasing dramatically in rangelands of the Southwest and Great Plains. We apply a common framework to evaluate and compare the effects of climate change on woody plant encroachment in these two regions, including 1) the direct effects of increasing temperature, atmospheric CO2, and changing precipitation patterns on woody plant establishment and growth, 2) the indirect effects of climate on woody plant establishment, growth, and survival mediated by the responses of herbaceous plants and changes in competition for water and disturbance by fire, 3) the effects of woody plant encroachment on ecosystem services, 4) the responses of land managers and supporting institutions to woody plant encroachment in the form of brush management, prescribed grazing, and prescribed fire practices, and 5) the effects of management strategies on ecosystem services. In the Southwestern US and southern Great Plains, the effects of increasing dryness and precipitation variability on woody plant encroachment are already apparent—with clear evidence of shrub increases depending on soil type and elevation. In the central and northern Great Plains, increased interannual variability in precipitation is masking declines in rangeland production resulting from woody encroachment – which reduces rancher readiness to prevent further woody expansion and production losses. In all rangeland regions, as woody plants saturate the landscape, encroachment rates become independent of grazing management. Woody encroachment is occurring even in areas where prescribed fires match or exceed historical fire return intervals. Brush management using selective herbicides (for resprouters) or mechanical removal (for non-resprouters) has limited effectiveness at large scales. For these reasons, rangeland professionals are encouraged to be more strategic in their management of woody encroachment. This includes the application of concepts that reduce vulnerability to woody encroachment in a changing climate, identifying where opportunities exist to manage woody encroachment more effectively for key ecosystem services, and where encroachment is already in advanced stages and locations where new planning efforts are considering how to manage ecosystem service benefits and trade-offs in woody-dominated rangelands.