DOI: 10.5061/dryad.sf7m0cg6f
title: Community composition influences ecosystem resistance and productivity more than species richness or intraspecific diversity

description: Biodiversity describes the variety of life and may influence properties
 and processes of ecosystems, such as biomass production and resistance to
 disturbance. We investigated the effects of multiple facets of
 biodiversity – species richness and composition of the community, and
 intraspecific diversity in two key species – on both production and
 resistance of experimentally-assembled biological soil crusts (biocrusts).
 We found that productivity was most strongly influenced by community
 composition (variation in the presence and relative proportions of
 community members), and weakly positively influenced by species richness.
 Intraspecific diversity, encompassing both the richness and composition of
 clones, had a neutral effect on community productivity within one focal
 species (Syntrichia caninervis), but a moderately negative effect on
 productivity within the other focal species (S. ruralis). Resistance was
 also most strongly influenced by community composition, although different
 sets of species contributed most to resistance and production. Resistance
 was not affected by either species richness or intraspecific diversity in
 either focal species. Our findings supported our general expectation that
 community-level facets of biodiversity would be more influential than
 intraspecific diversity within a species because trait variability among
 species is usually greater than that within. These results also indicated
 that although species richness is often thought to strongly affect both
 productivity and resistance, the presence, absence and relative abundance
 of particular species may be more influential to both. Simultaneous
 manipulation of multiple facets of biodiversity in experiments may lead to
 a more complete understanding of the variety of ways in which biodiversity
 may regulate ecological systems.
description: <strong>Please see manuscript and supplemental
 material</strong> (Community composition influences ecosystem
 resistance and productivity more than species richness or intraspecific
 diversity) in Oikos. Briefly: Mosses and lichens were
 seeded into experimental pots, crossing species richness with clonal
 richness within a focal moss genus. We repeatedly monitored total cover of
 the developing communities using an NDVI threshold and repeat photos.
 Cover data was standardized for each time point relative to calculated
 initial conditions. We initiated a resistance phase for the final three
 time points, during which growing conditions wer emuch more stressful. For
 these time points we also calculated a resistance value which is the
 decline in standardized cover at a given time point, relative to the most
 productive point prior to the resistance phase.
description: <strong>Please see manuscript and supplemental
 material</strong> (Community composition influences ecosystem
 resistance and productivity more than species richness or intraspecific
 diversity) in Oikos. There are some missing cover
 values resulting from missing or poor quality photos that could not be
 assessed.