Effects of realistic biodiversity loss on ecosystem functioning are mediated by varying resource availability across time and space

Background/Question/Methods

Most studies of the relationship between biodiversity and ecosystem function have examined randomized diversity losses, although in natural systems biodiversity loss tends to occur progressively rather than randomly. Many studies now support the finding that realistic biodiversity loss generally leads to greater effect sizes on ecosystem functioning than random biodiversity loss; however, none of these studies span multiple years and we know little about how the effects of realistic biodiversity loss on ecosystem functioning are mediated by resource availability that varies spatially and temporally. In this study, we ask how productivity and invasion resistance are differentially affected by realistic versus randomized diversity loss across a soil depth gradient over several years of variable rainfall. Data were collected for three years from an experimental, field-based biodiversity manipulation in a California serpentine grassland.

Results/Conclusions

We found that climatic conditions across years and soil-depth variation across space differentially and interactively influenced the effect sizes of realistic versus randomized biodiversity loss. The realistic diversity loss treatment showed increasing exotic biomass with decreasing diversity in the two higher-rainfall years, but there was no effect of diversity in the below-average rainfall year. This effect was reversed for the randomized diversity loss treatment. The overall effect of soil depth on invasive biomass was strongest in the wettest year. Overall, these results suggest that the effects of realistic biodiversity loss on ecosystem functioning are not only a factor of the driver of diversity loss and which species are lost, but also how the remaining species interact with variable environmental conditions.