Ecology and restoration of Erodium macrophyllum

Invasive species are the primary cause of extinction next to direct habitat loss. In California, grasslands have been heavily invaded by Mediterranean grasses and forbs. Most grassland studies have focused on the impact of invasive grasses on native grasses, even though native forbs represent a large proportion of total grassland diversity and exotic forbs are ubiquitous. Erodium macrophyllum is a rare grassland forb found in California, southern Oregon and northern Baja California. While historical evidence suggests that E. macrophyllum may once have been more common and occurred in several habitats, recent observations indicate that it is restricted to clay soil outcrops. The decrease in abundance and distribution coincide with the invasion of exotic species into California. The central question guiding this research is, what limits the distribution of E. macrophyllum? While many studies often look at a single factor affecting the fitness or distribution of a species, I took a broader approach and investigated the roles of soil type, soil microorganisms, competition and fire and how they affect growth and possibility distribution of E. macrophyllum. Specifically, through a series of greenhouse and field experiments and herbaria searches, I investigated (1) its historical and present distribution, and habitat characteristics, (2) how its growth is affected by soil type and different mycorrhizal communities, (3) how different competitors in an exotic annual grassland affects its growth in non-clay soils, (4) how fire and competition with exotic grasses affect its demography in a native perennial grassland and (5) the population growth rates of restored populations in a perennial grassland, an exotic grassland and a naturally occurring population of E. macrophyllum and which life-history stages are most sensitive to different competitors in each of these habitats. There are approximately 100 documented populations of E. macrophyllum throughout its range, and despite its restriction to clay soils, it can grow and reproduce on other soil types, often to a greater extant than on clay. Similarly, mycorrhizal inoculum increases its growth, but soil type has a larger effect. Erodium macrophyllum is severely affected by competition with both native and exotic species and fire. Fire, while it can decrease establishment, it can increase fecundity. However, establishment is probably more important than fecundity to overall population growth. Erodium macrophyllum is severely impacted by competition with native and exotic forbs, and this may be part of the reason why it is restricted to clay soils.