Mycorrhizal inoculation can enhance outcomes of ecological restoration but the factors that influence restoration outcomes are little explored. We searched the literature for field studies of mycorrhizal inoculation to identify factors that determine benefits to ecological restoration. We assessed 34 studies of plant growth (biomass) and plant species richness responses to mycorrhizal inoculation, and their dependence on six explanatory factors: plant identity (plant functional group), soil conditions (soil pH, concentrations of total N and plant-available P), disturbance history (severity of soil disturbance) and fungal identity (single species to whole soil inoculum). We also assessed the development of inoculation effects over time. Our analysis revealed that inoculation with mycorrhizal fungi enhanced plant growth in restored grasslands, shrublands and woodlands spanning semi-arid to mesic sites around the world. The effect was substantial, increasing plant biomass by an average of 1.7 across the 26 studies that measured biomass, and tended to increase over time. A subset of studies examined plant species richness and similarity of restored species composition to the reference communities. In these studies, mycorrhizal inoculation increased species richness of restored plant communities by an average of 30%, and increased the similarity of restored communities to reference communities. Inoculation was most beneficial to plants with greater nutrient demand (woody nitrogen-fixers), plants with inefficient nutrient-uptake (C4-grasses) and plants growing on severely disturbed or nutrient-poor soils (i.e., low in total nitrogen or plant-available phosphorus). Overall, we conclude that mycorrhizal inoculation can promote plant growth and plant species richness in field conditions to improve the outcomes of ecological restoration projects.
Neuenkamp L., Prober, S.N., Price, J.N., Zobel, M., Standish, R.J. 2018. Benefits of mycorrhizal inoculation to ecological restoration depends on plant functional type, restoration context and time. Fungal Ecology (in press).