Shrub persistence and increased grass mortality in response to drought in dryland systems

Global Change Biology
By: , and 

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Abstract

Droughts in the Southwest U.S. have led to major forest and grassland die‐off events in recent decades, suggesting plant community and ecosystem shifts are imminent as native perennial grass populations are replaced by shrub‐ and invasive plant‐dominated systems. These patterns are similar to those observed in arid and semiarid systems around the globe, but our ability to predict which species will experience increased drought‐induced mortality in response to climate change remains limited. We investigated meteorological drought‐induced mortality of nine dominant plant species in the Colorado Plateau Desert by experimentally imposing a year‐round 35% precipitation reduction for eight continuous years. We distributed experimental plots across numerous plant, soil, and parent material types, resulting in 40 distinct sites across a 4500 km2 region of the Colorado Plateau Desert. For all eight years we tracked ca. 400 individual plants and evaluated mortality responses to treatments within and across species, and through time. We also examined the influence of abiotic and biotic site factors in driving mortality responses. Overall, high mortality trends were driven by dominant grass species, including Achnatherum hymenoides, Pleuraphis jamesii, and Sporobolus cryptandrus. Responses varied widely from year to year and dominant shrub species were generally resistant to meteorological drought, likely due to their ability to access deeper soil water. Importantly, mortality increased in the presence of invasive species regardless of treatment, and native plant die‐off occurred even under ambient conditions, suggesting that recent climate changes are already negatively impacting dominant species in these systems. Results from this long‐term drought experiment suggest major shifts in community composition and, as a result, ecosystem function. Patterns also show that, across multiple soil and plant community types, native perennial grass species may be replaced by shrubs and invasive annuals in the Colorado Plateau Desert.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Shrub persistence and increased grass mortality in response to drought in dryland systems
Series title Global Change Biology
DOI 10.1111/gcb.14667
Volume 25
Issue 9
Year Published 2019
Language English
Publisher Wiley
Contributing office(s) Southwest Biological Science Center
Description 15 p.
First page 3121
Last page 3135
Country United States
State Utah
City Moab
Other Geospatial Colorado Plateau Desert