Plant-soil feedback effects on germination and growth of native and non-native species common across Southern California.
Changes in plant assemblages can influence biotic and abiotic soil conditions. These changes can cause plant-soil feedbacks that can inhibit or facilitate plant germination and growth. Here, we contribute to a growing literature examining plant-soil feedbacks in the endangered sage scrub ecosystem by examining the germination and growth of Artemisia californica, the dominant native shrub species in the ecosystem, in soil conditioned by two widespread plant invaders (Brassica nigra, Bromus madritensis ssp. rubens), and the germination and growth of these invasive species in conspecific and heterospecific soils. Our findings suggest that: (i) A. californica soils can limit establishment of some species (B. nigra) but not others (B. madritensis), (ii) A. californica soil conditions reduce growth of all plant species, and (iii) non-natives are negatively impacted by soil microbes, but in some contexts can do better in heterospecific soil. As our findings were often incongruent with other studies that examined interactions among similar species at other sites, we suggest that we are at our infancy of understanding these complex interactions, and that developing a predictive framework for understanding plant soil feedbacks in the sage scrub ecosystem involves understanding how various plant species respond in different soil contexts within the ecosystem.