A plant soil feedback (PSF) is the modification of soil conditions by a plant that affects subsequent intra- or inter-specific plant performance.  The underlying assumption is that through carbon inputs into the soil, plants can influence or ‘engineer’ their environment in species specific ways.  Many PSF studies only examine the feedback using a bioassay or phytometer method in which soil is cultivated with specific plants and the only metric for the feedback is subsequent plant growth.  In this project, the bioassay method is used and responsible mechanisms for the PSF are examined.  The three mechanisms investigated are: changes in soil physical characteristics, soil microbial community and allelochemical exudation.  Investigating PSF may provide some insight into the success of invasive plant species.  Disparate abilities of plant species to generate PSF may help explain the efficiency of some invasive species in dominating a site.  Successful invaders may have increased ability to generate positive intraspecific PSF than natives.   By studying the PSF generation ability of 7 annual and perennial grasses both native to and invasive in the Great Basin, perhaps greater insight into both plant soil interactions and invasion dynamics will be gained.  

Results/Conclusions

    We have conducted a reciprocal transplant experiment in the greenhouse using native top soil and seven locally occurring grass species.  The grasses used included both annual and perennial grasses that are native to and exotic in the Great Basin:  Vulpia microstachys, Elymus elymoides, Pseudoroegneria spicata, Agropyron cristatum, Bromus tectorum, Aegilops triuncialis and Taeniatherum caput-medusae.  A first generation of grasses was grown to examine species specific changes in soil characteristics.  Soils were analyzed immediately before and after plant growth.  A second generation of grasses was then grown to examine the effects of the species specific alter soils on subsequent plant growth.  A full factorial combination was used so every grass species was grown in soil cultured by every grass species.  Plant performance in the second generation was measured by aboveground biomass production.  Preliminary results show low soil nitrogen concentrations (16.01 mg/kg NO₃ [SD 0.20] and 0.51 mg/kg NH₄  [SD 0.05] ) via KCl extraction and no detectable P from miscible displacement analysis.  Preliminary results also show invasive grasses (especially Aegilops triuncialis) produce substantially more aboveground biomass than natives under greenhouse conditions.