Magnitude shifts in aeolian sediment transport associated with degradation and restoration thresholds in drylands

Authors: Webb, Nicholas; WHEELER, BRANDI - New Mexico State University; EDWARDS, BRANDON - New Mexico State University; SCHALLNER, JEREMY - Bureau Of Land Management; MACANOWICZ, NEESHIA - New Mexico State University; Van Zee, Justin; Courtright, Ericha; COOPER, BRAD - New Mexico State University; McCord, Sarah; Browning, Dawn; DHITAL, SAROJ - New Mexico State University; Young, Kristina; Bestelmeyer, Brandon

Submitted to: Journal of Geophysical Research-Biogeosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2025
Publication Date: 3/7/2025
Citation: Webb, N.P., Wheeler, B., Edwards, B.L., Schallner, J.W., Macanowicz, N., Van Zee, J.W., Courtright, E.M., Cooper, B., McCord, S.E., Browning, D.M., Dhital, S., Young, K.E., Bestelmeyer, B.T. 2025. Magnitude shifts in aeolian sediment transport associated with degradation and restoration thresholds in drylands. Journal of Geophysical Research-Biogeosciences. 103(3):e2024JG008581. https://doi.org/10.1029/2024JG008581.
DOI: https://doi.org/10.1029/2024JG008581

Interpretive Summary: In this study, we investigate how dryland vegetation change can influence wind-driven sediment transport. We use measurements of vegetation composition, cover, and structure (height and spacing) collected in the northern Chihuahuan Desert to understand change in sediment transport by wind in different ecological states, representing historical grassland and alternative vegetation communities that have resulted from shrub invasion and degradation and restoration processes that affect grass cover. Our results show over four orders-of-magnitude change in sediment transport rates following a trajectory of degradation, and a decrease in sediment transport rates over the same range in response to grass recovery. Sediment transport rates were highly sensitive to degradation and restoration thresholds between alternative ecological states, suggesting that patterns of wind erosion in vegetated drylands are likely determined by patterns of vegetation disturbance and recovery that are often unique to different soil types and landscape settings.

Technical Abstract: Vegetation change in drylands can influence wind erosion and sand and dust storms (SDS) with far-reaching consequences for Earth systems and society. Although vegetation is recognized as an important control on wind erosion and SDS, the interactions are not well described at the landscape level or in the context of dryland ecosystem change. The transition of sites from one ecological state to another (e.g., grassland to shrubland) is typically associated with changes in the composition, cover, and structure of vegetation, which influence drag partitioning and wind shear velocities that drive aeolian sediment transport. Here, we quantify the magnitude and direction of aeolian sediment transport responses to ecological state change in the northern Chihuahuan Desert and identify thresholds associated with state transitions. Our results show aeolian sediment mass flux (Q) increased from ~1 to 10 g m-1 d-1 in historical grassland with scattered shrubs to ~10–100 g m-1 d-1 following shrub invasion and decline in perennial grass cover to ~100–10,000 g m-1 d-1 in shrubland following complete grass loss. The magnitude shifts were associated with critical perennial grass cover thresholds governing nonlinear increases in Q across ecological state transitions. Grass recovery in shrubland reduced Q to rates similar to those in historical grasslands—a multiple order of magnitude reduction. Our results show that crossing degradation and restoration thresholds between alternative ecological states can have a profound effect on the magnitude and spatiotemporal variability of aeolian sediment transport and primacy in determining patterns of wind erosion and dust emissions in vegetated drylands. Plain Language Summary In this study, we investigate how dryland vegetation change can influence wind-driven sediment transport. We use measurements of vegetation composition, cover, and structure (height and spacing) collected in the northern Chihuahuan Desert to understand change in sediment transport by wind in different ecological states, representing historical grassland and alternative vegetation communities that have resulted from shrub invasion and degradation and restoration processes that affect grass cover. Our results show over four orders of magnitude change in sediment transport rates following a trajectory of degradation and a decrease in sediment transport rates over the same range in response to grass recovery. Sediment transport rates were highly sensitive to degradation and recovery thresholds between alternative ecological states, suggesting that patterns of wind erosion in vegetated drylands are likely determined by patterns of vegetation disturbance and recovery that are often unique to different soil types and landscape settings. Key Points: Aeolian sediment transport rates changed over four orders of magnitude across grassland to shrubland ecological states Critical perennial grass cover thresholds for magnitude shifts in transport rates were associated with ecological state transitions Results suggest that ecological state is a primary control on aeolian sediment transport and dust emissions from vegetated drylands