UC Berkeley

Ecological restoration has become a large enterprise driven by regulatory policies and by public and private initiatives. Regulatory agencies and ecologists call for use of propagules that are adapted to project sites, compatible with other species, and genetically diverse. This project uses a native California grass, Stipa pulchra, to ask whether the cost-management practice of collecting seeds from dense stands of target species can have unintended selective effects on species used in restoration. Absolute cover, standing biomass, species composition, and S. pulchra density and culm count were recorded on plots in three central California sites. S. pulchra seeds from these plots were sown in pots allocated to two watering groups and three temporal blocks.

Pot-study plants grown from seed collected from plots with greater absolute cover and S. pulchra density had significantly higher basal diameters, tiller counts, and root: shoot ratios. Plants derived from less-competitive plots reproduced earlier and gave rise to more culms. These results indicate that distribution of S. pulchra genoypes in the field may reflect a competition: colonization pattern, with more fecund S. pulchra plants inhabiting less-competitive patches than those occupied by their more-competitive conspecifics. Other aspects of pot-study plant growth appeared to reflect background vegetation of the field plots. Although plants grown from seeds collected at the three sites were significantly different, there was no evidence that ecological distance reflected geographic distance. Plants receiving more water had relatively greater aboveground growth and lower root: shoot ratios. Statistical interactions of blocking and watering treatments with site may reflect plant adaptation to climate and soil at the various sites. Implications of these results apply to environmental restoration and extend to ecological research, where nonrandomly collected propagules are often used to represent genetic characteristics of entire populations.