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

摘要: Droughts in the southwest United States have led to major forest and grassland die-off events recent decades, suggesting plant community ecosystem shifts are imminent as native perennial grass populations replaced by shrub- invasive plant-dominated systems. These patterns similar those observed arid semiarid systems around globe, but our ability predict which species will experience increased drought-induced mortality response climate change remains limited. We investigated meteorological of nine dominant Colorado Plateau Desert experimentally imposing a year-round 35% precipitation reduction for eight continuous years. distributed experimental plots across numerous plant, soil, parent material types, resulting 40 distinct sites 4,500 km2 region Desert. For all 8 years, we tracked c. 400 individual plants evaluated responses treatments within species, through time. also examined influence abiotic biotic site factors driving responses. Overall, high trends were driven including Achnatherum hymenoides, Pleuraphis jamesii, Sporobolus cryptandrus. Responses varied widely from year shrub generally resistant drought, likely due their access deeper soil water. Importantly, presence regardless treatment, occurred even under ambient conditions, that changes already negatively impacting these Results this long-term drought experiment suggest composition and, result, function. Patterns show that, multiple may be shrubs annuals