Using plant functional traits to guide restoration: A case study in California coastal grassland

Restoration ecology can benefit greatly from developments in trait‐based ecology that enable improved predictions of how the composition of plant communities will respond to changes in environmental conditions. Plant functional traits can be used to guide the restoration of degraded habitats by closely tailoring treatments to the local species pool. We tested this approach in two heavily invaded coastal California grasslands. We asked whether native plant abundance and plant community trait composition respond to (1) experimental soil fertility reduction in the form of twice‐yearly carbon (C) amendments and (2) disturbance in the form of mowing. We measured height, specific leaf area, leaf thickness and leaf density from individuals of 39 species in the control and C addition plots, and supplemented these trait values with database information on growth form, lifespan, nitrogen‐fixing ability and seed mass.  Consistent with theoretical predictions, C addition favored short, large‐seeded and nitrogen‐fixing species, while mowing benefitted short species with high specific leaf area. However, native and exotic species did not differ in any of the measured traits, and neither group benefitted generally from the treatments. Carbon addition led to large intraspecific trait shifts, with individuals in C addition plots having smaller, denser leaves and shorter stature. Species' trait plasticity, however, was not related to the community composition response to C addition.  Our study indicates that trait‐based ecology is sufficiently mature to provide useful predictions in the realm of restoration ecology. Trait screening at a site can help predict the success of a particular restoration measure in that community.