Desert shrub responses to experimental modification of precipitation seasonality and soil depth: relationship to the two‐layer hypothesis and ecohydrological niche

摘要: Summary Ecohydrological niches are important for understanding plant community responses to climate shifts, particularly in dry lands. According the two-layer hypothesis, selective use of deep-soil water increases growth or persistence woody species during warm and summer periods thereby contributes their coexistence with shallow-rooted herbs ecosystems. The resource-pool hypothesis further suggests that shallow-soil benefits all plants while primarily enhances physiological maintenance survival species. Few studies have directly tested these by manipulating availability observing long-term outcomes. We predicted factors promoting infiltration storage deep soils, specifically greater winter precipitation soil depth, would enhance Artemisia tridentata (big sagebrush) cold, winter-wet/summer-dry desert. Sagebrush 20 years irrigation were compared summer- no irrigation, on plots having relatively shallow soils (2 m vs. 1 m depths). Winter increased sagebrush cover, crown canopy volumes, but not density (individuals/plot) plots. On plots, surprisingly decreased shrub cover size, had effect. Furthermore, multiple regression suggested variations related (i) firstly (0–0.2 m) secondly deeper (> 1 m deep) (ii) more springtime than midsummer water. Water-use efficiency considerably without was lowest irrigation. Synthesis. responsive seasonal timing total annual precipitation. Factors enhanced deep-water (deeper plus precipitation) led consistent contribution hypothesis. However, also negative effects sagebrush, suggesting an ecohydrological trade-off considered theories. interaction between depth indicates could lead a mosaic decreases A. tridentata across landscapes variable depth.