Shrubs Facilitate Perennial Bunchgrass Recruitment in Drylands under Experimental Precipitation Change

Increasing extremes in climate related weather events pose a major threat to plant recruitment in drylands. Research has shown facilitation effects by shrubs to improve recruitment in arid regions, however it remains unclear if these effects vary between soil types, early life stages and in both severe precipitation and drought events. We test if shrubs facilitate abundance of both seedlings and juveniles between two soil types in artificial high precipitation, ambient and severe drought conditions. When the effect of shrubs was considered, seedling and juvenile responses were similar between sites. Shrubs increased seedling abundance by 40.9% in drought. In high precipitation, shrubs increased seedling abundance by 20% at one site and juvenile abundance 15% at both sites. These findings support the notion that shrubs can improve recruitment in both severe precipitation and drought years, but the strength of this effect varies with soil. Our results indicate that resource islands generated by shrubs in high precipitation years, may be an important factor driving population dynamics in arid systems as years oscillate between wet and dry.