Interactive Effects of Microbial Community Structure and Soil Moisture on Wyoming Big Sagebrush Performance
Efforts to restore degraded areas of the North American sagebrush steppe have been largely unsuccessful. Given the importance of mycorrhizal fungal communities to sagebrush fitness, this lack of success may be due to poor interactions between sagebrush ecotypes and unfamiliar soil fungi, as seed for restoration is often sourced from distant locations. To evaluate the importance of fungal-sagebrush interactions on sagebrush reestablishment I asked: (1) How does inoculation with ‘coevolved’ versus ‘foreign’ fungal inoculum impact sagebrush fitness? And (2) How does drought modify the advantage different fungal communities provide? I conducted a greenhouse experiment in which Wyoming Big Sagebrush seed sourced from the wet end of its range was grown in sterilized soil with fungal inoculum sourced from either the same wet site as the seeds or a drier foreign sagebrush-dominated site, and subjected them to either a moist climate treatment that mimicked the precipitation at the home site or a dry climate treatment that mimicked the precipitation at the drier site. Sterilized versions of both inocula under both precipitation regimes served as controls, producing eight treatment combinations (n=5).
Analysis of the soil fungal community structure using Illumina sequence data demonstrated that inoculumX precipitation treatments differed in fungal community composition in the rhizosphere of seedlings at the end of the greenhouse growth period. I detected evidence of adaptation of the soil fungal community to local environmental conditions, where the presence of live inoculum enhanced biomass and specific root length of seedlings, but only when plants were grown under the same precipitation regime as the site from which the inoculum was sourced. Based on these results, applying local-environmentally-adapted microbial inoculum from the site of intended restoration could potentially help improve sagebrush establishment.