PARENT SESSION
Poster Session # 7: Restoration, Resource Management, and Conservation.

Monday, August 4 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Reconstruction of California native grasslands.

Solomeshch, Ayzik^{1, 2}, Barbour, Michael^*,1, ¹ University of California, Davis, CA, USA² Institute of Biology Russian Academy of Science, Ufa, Russia

ABSTRACT- California interior grassland covering about 25% of the state is dominated by non-native annuals and represents a dramatic example of large-scale species replacement. The change over the past 250 years occurred so rapidly, and so early, that no descriptions exist for their pre-contact botanical composition. Range of alternative opinions includes chaparral, broadleaved forest, annual grasses, and rhizomatous grasses. Nevertheless a widely accepted paradigm is that they were originally dominated by perennial bunchgrasses Nassella cernua and N. pulchra, associated with half a dozen other perennial grasses (Clements 1920). But because of the pervasive extent of exotics, the composition of pre-contact Californian grasslands has never been reconstructed with any degree of assurance (Hamilton 1997). A resolution of this uncertainty would have enormous restoration and conservation importance. We assume it has remained so long unsolved because of a past focus on dominant species, which have been completely replaced and may not be used as a strong evidence for any of expressed opinions. We test the bunchgrass hypothesis analyzing the complete floristic assemblages of 55 modern grasslands sampled in Sacramento area, giving particular emphasis to native species that are now typically neither abundant nor dominant. It was shown, that despite the low abundance of native species, their contribution to a-diversity is much greater (r=0.87) than the statistically insignificant contribution of exotics (r=0.11). Both detrended correspondence analysis and classification of stands according to Braun-Blanquet approach confirms that the five groups of plots were floristically distinct. Ratio between native and exotic species and life form spectra differ from stand to stand, indicating degree of species replacement. Nassella pulchra among others native species exhibited significant positive correlations (r=0.320) with total cover of invasive species. Bunchgrass paradigm does not explain variety of native species assemblages in modern grasslands. Our results support the alternative hypothesis, that it was a heterogeneous and complex mosaic, with floristically different communities occurring on an array of different microhabitats at a relatively fine scale.

Key words: bunchgrasses, invasion, California grasslands, Nassella pulchra