Selective mortality leads to competitive release of a foundational perennial grass in an aridifying grassland
- 1Department of Ecology, Montana State University, Bozeman, MT US
- 2Southwest Biological Science Center, U.S. Geological Survey, Moab, UT USA
- 3Crops Research Laboratory, USDA-ARS Rangeland Resources and Systems Research Unity, Fort Collins, CO USA
Abstract
Vegetation dynamics in dryland ecosystems are defined by competition for water, a limiting and increasingly variable resource. As aridification creates warmer and drier conditions, with more frequent and intense droughts, the nature of competitive relationships may be altered, leading to changes in community composition. Reduced water availability is expected to decrease the cover and abundance of cool-season C3 grasses on the Colorado Plateau, with unknown impacts on other plant functional types, such as drought-tolerant C4 species. Here, we explore the effects of competitive release on Pleuraphis jamesii, a dominant C4 grass with rooting and photosynthetic traits that may enable it to capitalize on the mortality of less drought tolerant C3 species. To accomplish this, we used herbicide to create three removal treatments (C3 grass and forb removal, C4 grass removal, and control (no removal)) surrounding P. jamesii focal individuals and measured the subsequent impacts on water availability and plant water relations and growth. The experimentally induced mortality resulted in greater water availability for focal individuals in the C3 removal treatment. Increased water availability in C3 removal plots translated to less water stress and greater biomass production of focal P. jamesii plants, suggesting that competitive release can serve as the basis for shifts in community composition towards drought tolerant C4 plants observed regionally. These responses were not observed in the C4 removal treatment despite removing roughly equivalent amounts of total plant cover. Our results suggest that reductions in C3 competitors may benefit drought-tolerant C4 species through increased resource availability. These findings contribute to a mechanistic understanding of competitive interactions in increasingly water-limited systems.
Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1007/s00442-026-05935-0.
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BibTeX
@article{hoyskubik2026selective,
title = {{Selective mortality leads to competitive release of a foundational perennial grass in an aridifying grassland}},
author = {Sean L. Hoy-Skubik and David L. Hoover and Alix A. Pfennigwerth and Anna C. Knight and Michael C. Duniway},
journal = {Oecologia},
year = {2026},
month = oct,
doi = {10.1007/s00442-026-05935-0},
url = {https://doi.org/10.1007/s00442-026-05935-0},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Selective mortality leads to competitive release of a foundational perennial grass in an aridifying grassland
AU - Sean L. Hoy-Skubik
AU - David L. Hoover
AU - Alix A. Pfennigwerth
AU - Anna C. Knight
AU - Michael C. Duniway
PY - 2026
DA - 2026/10/27
JO - Oecologia
DO - 10.1007/s00442-026-05935-0
UR - https://doi.org/10.1007/s00442-026-05935-0
AB - Vegetation dynamics in dryland ecosystems are defined by competition for water, a limiting and increasingly variable resource. As aridification creates warmer and drier conditions, with more frequent and intense droughts, the nature of competitive relationships may be altered, leading to changes in community composition. Reduced water availability is expected to decrease the cover and abundance of cool-season C3 grasses on the Colorado Plateau, with unknown impacts on other plant functional types, such as drought-tolerant C4 species. Here, we explore the effects of competitive release on Pleuraphis jamesii, a dominant C4 grass with rooting and photosynthetic traits that may enable it to capitalize on the mortality of less drought tolerant C3 species. To accomplish this, we used herbicide to create three removal treatments (C3 grass and forb removal, C4 grass removal, and control (no removal)) surrounding P. jamesii focal individuals and measured the subsequent impacts on water availability and plant water relations and growth. The experimentally induced mortality resulted in greater water availability for focal individuals in the C3 removal treatment. Increased water availability in C3 removal plots translated to less water stress and greater biomass production of focal P. jamesii plants, suggesting that competitive release can serve as the basis for shifts in community composition towards drought tolerant C4 plants observed regionally. These responses were not observed in the C4 removal treatment despite removing roughly equivalent amounts of total plant cover. Our results suggest that reductions in C3 competitors may benefit drought-tolerant C4 species through increased resource availability. These findings contribute to a mechanistic understanding of competitive interactions in increasingly water-limited systems. Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1007/s00442-026-05935-0.
SN - 0029-8549
SN - 1432-1939
ER -