PS 27-120
Ecological restoration methods influence soil fungal activity
Arbuscular mycorrhizal fungi (AMF) assist in ecosystem restoration by facilitating native plant establishment and improving nutrient uptake by plants. In landscapes invaded by non-mycorrhizal Brassica nigra (mustard) plants, mowing and herbicide use are common methods for removing invasives. Mustard plants elicit allelopathic effects that may increase environmental stress and suppress fungal growth. Mowing and herbicide may also alter the abiotic environment and influence the percentage of native plant roots colonized by AMF, with consequences for native plant establishment. We hypothesized that AMF root colonization would be higher in herbicide-treated soils than mowed soils because herbicide desiccates mustard tissues while mowing permits mustard roots to persist. To compare restoration methods, we collected soils from unmanaged control plots that were severely invaded by mustard versus plots treated with either mowing (with thatch removal) or herbicide (grow kill cycles with broad-spectrum glyphosate sprayed to flush the invasive seed-bank from soil) to remove mustard. These soils were used to assay the AMF community by “baiting” the fungi with native Stipa pulchra grasses. Growth of Stipa pulchra seedlings was monitored weekly. After 90 days, the bioassays were harvested, and plant roots were stained to assess AMF percent colonization in grass roots, compared across restoration methods.
Results/Conclusions
Our hypothesis that AMF root colonization would be higher in herbicide-treated soils than mowed soils was supported. In the first 25 days of the plant bioassay, Stipa pulchra seedlings planted in soil from plots sprayed with herbicide were significantly taller than seedlings planted in soils from mowed or unmanaged control plots. By the 70th day, however, there were no significant differences among any of the three treatments. Stipa pulchra roots from plots receiving herbicide were significantly more colonized by AMF than were roots from mowed or unmanaged control plots. This suggests that the AMF community in landscapes invaded by mustard are more likely to recover when mustard is removed by herbicide than when mustard is mowed. We conclude that the effect of specific restoration methods on AMF activity could have management implications for grasslands invaded by mustard.