Plant diversity effects on carbon cycling in the Arctic
The relationship between biological diversity and ecosystem function (BEF) has been described generally by a number of hypotheses; however, most studies suggest a positive, saturating relationship between biodiversity and ecosystem function. The vast majority of BEF studies focus on experimentally constructed communities, but relatively little is known about what this relationship looks like across naturally assembled communities or when considering multiple dimensions of biodiversity. We examine the relationship between two dimensions of plant diversity – taxonomic and functional – and ecosystem CO2 fluxes across 16 plots, of naturally varying species diversity, located near the Toolik Lake Arctic Long Term Research Station (ARC LTER) in the northern foothills of the Brooks Range, Alaska (68°38’N and 149°43’W, 760 m a.s.l.). As high-latitudes are experiencing rapid warming and subsequent potential shifts in biodiversity and the cycling and storage of carbon and nutrients, it is timely to explore the role plant diversity plays in ecosystem functioning within an Arctic context.
Using structural equation modeling to examine the relationship between different dimensions of diversity and ecosystem function (CO2 flux), we found positive associations between plant diversity and CO2 flux. As structural equation modeling is a multivariate statistical method that allows for an evaluation of various relationships between explicit (direct or manifest) and latent variables, we were able to compare the relative strengths and associations between plant taxonomic and functional diversity on ecosystem function and found that functional diversity has a stronger effect on CO2 flux than taxonomic diversity. Increasing evidence demonstrates that plant diversity is declining in the Arctic, due to warming and changing soil nutrient availability, ultimately contributing to deciduous shrub expansion, and our findings suggest that such biodiversity declines will likely have important effects on the cycling and storage of carbon in the Arctic.