Data from: Effects of native bryophytes on exotic grass invasion across an environmental gradient

Understanding the role that native biodiversity plays in controlling
exotic species invasion is a critical goal in ecology. In terrestrial
plant communities, most research has focused on the effects of native
vascular plants on invasion by exotic vascular plants. However, in many
ecosystems, native bryophytes and other non-vascular plants are common and
can affect the establishment, survival and growth of vascular plants. A
more complete picture of how native biodiversity affects exotic plant
invasion, demands that more studies measure the effects of native
bryophytes on exotic vascular plants. Moreover, there is growing
realization that the effects of native species on invaders can range from
negative to positive and that a complete picture of interactions between
native and exotic plants requires measuring interactions in multiple
environments. We used both observational and experimental studies to
quantify the effects of native moss on two exotic annual grass species
along a 200-m environmental gradient in a coastal dune in northern
California. We found the effects of bryophytes to be species-specific and
to vary with environmental context. Bryophytes facilitated the survival of
one exotic grass species at both ends of the environmental gradient. For
the other exotic grass species, bryophytes reduced survival at one end of
the environmental gradient and had no effect at the other end. Our
findings provide an important test of the effects of native bryophytes on
exotic vascular plant invasion, and importantly show that these effects
can vary dramatically even across local environmental gradients.