Cover Stories: Issue 107 Volume 5

The cover image for Journal of Ecology’s latest issue was taken by Marina LaForgia. Author of “Functional diversity is a passenger but not driver of drought‐related plant diversity losses in annual grasslands.” First author, Jesse E.D. Miller, gives us more details on the research behind the photo.


This article is part of our latest Special Feature: Is Phylogenetic and Functional Trait Diversity a Driver or a Consequence of Grassland Community Assembly?


Climate change is producing warmer, drier conditions in many global ecosystems, but the effects of these altered conditions on plant diversity are still not fully understood. Theory predicts that high functional diversity – the coexistence of species having a wide array of ecological strategies – may make communities stable and resilient in the face of disturbances. In this study, we asked how the diversity of functional traits in California grasslands interacted with prolonged drought.

Native wildflowers Lasthenia californica, Trifolium fucatum and Microseris douglasii bloom on a rocky serpentine outcrop in an annual grassland. North Coast Range, Lake County, California. Photo: Marina LaForgia


One challenge to understanding long-term change in plant communities is that high-quality, long-term plant community datasets are rare. In this study, we used a unique dataset to examine changes in plant functional diversity—a network of 80 study plots that has been monitored for 19 years at the UC Davis McLaughlin Reserve, in California’s Inner North Coast Range. Previous analyses had shown that plant species richness decreased during the course of the study, as a result of increasingly dry winters.  In this region, winter is the season when spring-flowering annual plants exist as small seedlings, vulnerable to drying of surface soils.

We found that community functional diversity (measured as the range of plant traits represented in sets of co-occurring species) declined significantly over the 19 year study, in close parallel with the pattern of drier winters.  In particular, plant communities tended to lose some of their more water-demanding species, as indicated by having traits such as larger and thinner leaves. These losses appeared to drive the overall decline in functional diversity.

Landscape in the study area at the UC Davis MClaughlin Reserve. Photo: Marina LaForgia.


Contrary to theory linking functional diversity to stability, we did not find that communities that had higher functional diversity at the beginning of the study were more robust against losses of species over time.  In fact, the communities that lost the most species over time were the ones that began by having the most water-demanding species, as indicated by leaf traits. Our findings suggest that long-term community stability may depend less on functional diversity per se than on the particular functional traits that determine whether species can tolerate altered conditions.

Jesse E.D. Miller – University of California, Davis, USA


Read the full article online:Functional diversity is a passenger but not driver of drought‐related plant diversity losses in annual grasslands” by Miller et al.

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