Ecosystem multifunctionality increases with beta diversity in restored prairies

Abstract

The loss of biodiversity at local and larger scales has potentially dramatic effects on ecosystem functioning. Many studies have shown that ecosystem functioning depends on biodiversity, but the role of beta diversity, spatial variation in community composition, is less clear than that of local-scale (alpha) diversity. To test the hypothesis that beta diversity would increase ecosystem multifunctionality through variation in species functional traits, we gathered data on plant community composition, plant functional traits, and seven ecosystem functions across 29 restored prairies. We found that averaged multifunctionality (mean of seven ecosystem functions) increased with both taxonomic beta diversity and functional beta diversity. The abundance of the dominant species, big bluestem, played a more minor role, suggesting a limited role for the selection effect. Neither taxonomic nor functional alpha richness was associated with multifunctionality, though this finding may be sensitive to the identity of the functions included because alpha diversity was associated with some individual functions in opposing directions. These findings suggest that in systems structured largely by natural processes, beta diversity (a patchwork of functionally different plant communities) and dominant species abundance may be more important than alpha diversity in fostering ecosystem multifunctionality. These findings suggest the need for an increased focus on community heterogeneity to reestablish functional ecosystems during restoration.

Landscape context explains ecosystem multifunctionality in restored grasslands better than plant diversity

“…We also found that A. gerardii abundance is negatively correlated with pollinator resource availability and floral richness. Both of these functions are positively correlated with functional diversity, which is negatively correlated with A. gerardii abundance in our system (Grman et al 2018). This may indirectly cause pollinator resource availability and floral richness to trade off with aboveground biomass and decomposition (which increase with A. gerardii abundance; Appendix S1: Fig.…”

“…Big bluestem (Andropogon gerardii) is the dominant species in this system, and many other tallgrass prairies, making up 32% of the plant community (mean relative abundance across sites). Because it alters the local environment by producing large amounts of biomass, A. gerardii may affect ecosystem functions such as productivity and decomposition (Grman et al 2018).…”

“…Although some studies have shown that biodiversity has a stronger effect than environmental conditions on ecosystem function (Hooper et al 2012, Craven et al 2016, studies testing diversity-function theory at large spatial extents, across landscapes that vary in environmental conditions, are few (but see Duffy et al 2017 for examples). In contrast, dominant species may also correlate with ecosystem functions through trade-offs with diversity, where highly dominant species may reduce diversity (Grman et al 2018), in turn reducing functioning. Furthermore, natural systems often contain highly dominant species that can directly affect ecosystem functions (Smith and Knapp 2003).…”

“…Whereas diversity-ecosystem function studies have primarily focused on productivity as a measure of ecosystem function (Tilman et al 2013), studies now often consider ecosystem multifunctionality by evaluating the drivers of multiple different ecosystem functions concurrently (e.g. Gamfeldt et al 2013, van der Plas et al 2016, Grman et al 2018, Hautier et al 2018. Biodiversity should increase multifunctionality through the same mechanisms that it increases individual functions (but see Gamfeldt and Roger 2017).…”

“…Species dominance might impact multifunctionality if the traits of the dominant species affect multiple different ecosystem functions (Gamfeldt and Roger 2017). In contrast, dominant species may also correlate with ecosystem functions through trade-offs with diversity, where highly dominant species may reduce diversity (Grman et al 2018), in turn reducing functioning. Thus, the combined and independent effects of diversity, dominant species, and environmental conditions on multifunctionality need further study.…”