Soil crusts versus invasive annual grasses

Background/Question/Methods

Biological soil crusts are known to take decades or more to develop in arid systems, yet are key components of ecosystem integrity.  Not only do crusts significantly increase biodiversity of landscapes, but numerous studies have shown that they provide substantial resistance to invasion of exotic annual grasses.  Most of these studies have been controlled experiments at localized sites; few have examined how this resistance might play out at a landscape level.  The study presented here examined cover of biological soil crusts and annual grasses at approximately 800 sites across the state of Nevada, USA.  The study is further placed into the context of ecological and rare-species conservation in the southwest.

Results/Conclusions

The correspondence between biological soil crust cover and annual grass cover is found to be a logarithmically negative correlation, suggestive of mutual exclusion.  Remote sensing analyses are capable of mapping annual grass distribution over vast landscapes; resulting maps showing where grasses are minimally present may provide insight into the distribution of remnant biological soil crust communities.  Such remnants are important to conserve both for rare species and for potential seeding of surrounding landscapes for restoration of ecological function.