In the Sierra Nevada bioregion of California, a major factor limiting the use of native grasses in restoration is the lack of information on the scales of species adaptation across gradients in elevation and latitude.  The successful use of native grasses for restoration following disturbances such as fires and logging operations depends critically on the development of zones of adaptation for major restoration species.  Establishment of adaptive seed zones will allow governmental agencies and private groups to use native species more effectively and will help native seed companies to economically produce genetically appropriate germplasm for restoration. We describe the results of an extensive reciprocal transplant experiment conducted in six national forests (Plumas, Tahoe, Eldorado, Stanislaus, Sierra, and Inyo) plus the Lake Tahoe Basin Management Unit. The three species studied (Elymus glaucus, Elymus elymoides, and Bromus carinatus) are distributed widely in the Sierra Nevada bioregion and are important restoration species. Survivorship, morphological characters, and reproductive data from the common gardens were collected in a collaborative effort by U.S.D.A. Forest Service botanists over a three year period.

Results/Conclusions

Multivariate analyses of these data indicated that both latitude and elevation were important factors influencing scales of adaptation in these native grasses.  Interactive effects of latitude and elevation were also important in shaping the adaptive zones in these species.  Replication of both seed source populations and planting sites within broad climatic regimes allowed us to define a set of provisional seed zones for each species that reflects the specific ecology and evolutionary dynamics of each grass species. In addition to genetic differentiation in aspects of plant morphology and phenology, significant fitness differentials in both survival and reproductive potential were detected for all three species; indicating pronounced levels of local adaptation. Although further work may refine the specific ranges of the seed zones we present, we hope that these provisional zones will 1) provide guidance for the use of these species in restoration projects within the Sierra Nevada bioregion and 2) provide a model for the development of seed zones in other bioregions.