Linking environmental filters and functional traits to multiple ecosystem services

Background/Question/Methods

Provisioning of multiple ecosystems services – termed multifunctionality – is a critical component of natural resource management.  In order to effectively predict and manage for multifunctionality, it is important to understand to what extent various abiotic and biotic controls on ecosystem services exhibit antagonistic, synergistic or unrelated ecological processes.  In a California range landscape we assessed the potential for multifunctionality in forage production and carbon storage as a function of abiotic drivers, multiple aspects of plant functional traits and multivariate indices of functional diversity.  We tested a set of structural equation models varying in degree of complexity and the inclusion of abiotic effects via direct and indirect (via functional traits and diversity) mechanisms.

Results/Conclusions

We found elevation had a primarily indirect, negative effect on productivity via a reduction in the average height of the plant community at higher altitudes, due to a shorter growing season length.  In contrast, diversity of rooting architectures within a community, specifically variation in the allocation to coarse versus fine roots across species, was positively correlated with belowground productivity, which in turn had a strong positive effect on soil carbon.  Diversity of rooting architectures was independent of any environmental variables and of community-average height, resulting in moderate multifunctionality due to regulation of ecosystem services by orthogonal aspects of functional composition.  The most parsimonious model that explained both environmental modulation of functional traits as well as variation in both focal ecosystem services included only these two components of functional composition (average height and root architecture diversity), whereas models that included multivariate functional diversity indices did not explain significant variation in either forage production or carbon storage.  Our results demonstrate the importance of understanding environmental controls on aspects of biodiversity that may regulate different ecosystem services, and that such complex regulation of ecosystem services may be obscured through the use of composite multi-trait indices of functional diversity.