Warming reduces the cover, richness and evenness of lichen- dominated biocrusts but promotes moss growth: insights from an 8 yr experiment

Despite the important role that biocrust communities play in maintaining ecosystem structure
and functioning in drylands world-wide, few studies have evaluated how climate change
will affect them.
Using data from an 8-yr-old manipulative field experiment located in central Spain, we evaluated
how warming, rainfall exclusion and their combination affected the dynamics of
biocrust communities in areas that initially had low (< 20%, LIBC plots) and high (> 50%,
HIBC plots) biocrust cover.
Warming reduced the richness (35 6%), diversity (25 8%) and cover (82 5%) of
biocrusts in HIBC plots. The presence and abundance of mosses increased with warming
through time in these plots, although their growth rate was much lower than the rate of lichen
death, resulting in a net loss of biocrust cover. On average, warming caused a decrease in the
abundance (64 7%) and presence (38 24%) of species in the HIBC plots. Over time,
lichens and mosses colonized the LIBC plots, but this process was hampered by warming in
the case of lichens.
The observed reductions in the cover and diversity of lichen-dominated biocrusts with
warming will lessen the capacity of drylands such as that studied here to sequester atmospheric
CO2 and to provide other key ecosystem services associated to these communities.