Aeolian erosion increases drought susceptibility of grass seedlings relative to that of shrub invaders in a Chihuahuan Desert grassland

Authors: NIU, FURING - Gansu Agricultural Uiversity; Pierce, Nathan; SHI, YAFEI - Gansu Agricultural Uiversity; ARCHER, STEVEN - University Of Arizona; OKIN, GREGORY - University Of California (UCLA)

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2025
Publication Date: 11/20/2025
Citation: Niu, F., Pierce, N.A., Shi, Y., Archer, S.R., Okin, G.S. 2025. Aeolian erosion increases drought susceptibility of grass seedlings relative to that of shrub invaders in a Chihuahuan Desert grassland. Plant and Soil. (2025). https://doi.org/10.1007/s11104-025-08118-7.
DOI: https://doi.org/10.1007/s11104-025-08118-7

Interpretive Summary: The replacement of perennial grasses by unpalatable woody plants is a widespread form of degradation in arid and semiarid rangelands that is considered permanent on time scales relevant to land management. A well-documented consequence of this transition is an increase in bare soil that is exposed to wind erosion, which creates an abiotic feedback cycle that could promote shrub encroachment and diminish grass survival; these changes are expected to affect the establishment and growth of grass and shrub seedlings, especially under drought conditions, but so far this has not been directly tested. In a greenhouse experiment, seedlings of two native grass species had diminished growth in drought conditions, especially when grown in wind-eroded soil compared to intact soil. Conversely, growth of seedlings of an invasive shrub species was not as reduced in drought conditions and was comparable in both soil types. This disparity in drought susceptibility between grass and shrub seedlings on degraded soils may contribute to long-term shifts in arid grassland vegetation composition, ultimately facilitating shrub encroachment. Our findings offer valuable insights into the mechanisms underlying plant early establishment phase of shrub encroachment in dryland ecosystems, suggesting that once wind erosion occurs following vegetation loss, whether due to overgrazing, fire, or climate-induced drought, the resulting soil degradation initiates a feedback loop that further suppresses grass recruitment while enhancing shrub persistence, particularly during drought years.

Technical Abstract: Background and Aims Shrub encroachment is a widespread ecological state change in global arid grasslands, often driven by changes in disturbance regimes (e.g., livestock grazing). While various direct and indirect effects of grazing may promote grassland-to-shrubland transitions, the relative importance of these mechanisms remains unclear. A well-documented consequence of grazing and other disturbances is aeolian erosion, which reduces soil water and nutrient availability. We conducted a greenhouse experiment to ascertain whether such changes might favor shrubs establishment over that of grasses under drought conditions, potentially promoting shrub encroachment. Methods We quantified seedling establishment and growth of an aggressive grassland invader (Prosopis glandulosa) to that of two grass species (Bouteloua eriopoda and Sporobolus airoides) on wind-eroded (winnowed) and intact (non-winnowed) soils under contrasting watering regimes: control (FC, field capacity), medium drought (MD, 80% of FC), and severe drought (SD, 50% of FC). Results The combination of soil winnowing and drought negatively impacted growth of grass seedlings more than that of shrub seedlings. In well-watered (FC) conditions, seedling biomass was comparable (p'>'0.05) between soil types for all species. Under MD and SD, above- and belowground biomass declined, with the greatest reductions observed for seedlings on winnowed soils, particularly for the two grass species. Additionally, grass leaf production was reduced on winnowed soils, while that of the P. glandulosa shrub seedlings was unaffected. Conclusion These disparities in drought susceptibility on wind-eroded soils should give shrub seedlings a survival advantage in drought periods, thereby setting the stage for grassland-to-shrubland transitions.