Mycorrhizal fungi protect the soil from wind erosion : a wind tunnel study

Mycorrhizal fungi form symbiotic associations with the roots of most vascular plant species and can improve both plant growth and soil structure. Therefore, they are expected to play an important role in reducing soil erosion by wind. However, direct evidence for this is lacking, because it is hardly possible to separate the mycorrhizal effect from all other factors that influence wind erosion in natural environments. Here, we present laboratory wind tunnel experiments, which indicate that mycorrhizal fungi have the potential to substantially increase the protective effect of newly seeded plants against wind erosion. For root balls of two plant species (Lolium perenne and Anthyllis vulneraria ssp. alpestris), we found that the wind-induced soil loss decreased significantly with increasing percentage of root colonisation by mycorrhizal fungi. The mean soil loss of non-mycorrhizal control samples was more than twice as high as the one of mycorrhizal samples for A.¿vulneraria, whereas no significant difference was observed for L.¿perenne. These results are all the more remarkable because there was no mycorrhiza-induced plant growth enhancement. On the contrary, mycorrhizal plants had significantly smaller root systems than non-mycorrhizal plants in both species. Above-ground biomass was significantly smaller in mycorrhizal plants than in non-mycorrhizal plants for L.¿perenne but only slightly smaller for A.¿vulneraria. This study demonstrates that mycorrhizal fungi are able to help newly seeded plants to decrease the wind erodibility of soil, even in cases when they do not increase plant growth.