Effect of Removal of Garlic Mustard (Alliaria petiolata, Brassicaeae) on Arbuscular Mycorrhizal Fungi Inoculum Potential in Forest Soils

Abstract

Garlic mustard (Alliaria petiolata), a biennial species, is considered to be among the most troublesome of the invasive plants in the Eastern Deciduous forest of North America. It has been shown to prevent or reduce mycorrhizal colonization of native herbaceous ground layer plants and trees in these forests. It is estimated that 70-90% or more of herbaceous native ground layer plant species form associations with arbuscular mycorrhizal fungi (AMF). Loss of the mycorrhizal association can reduce growth, reproductive success, and competitiveness of plant species. Using a corn root bioassay, we examined the effect of garlic mustard removal on the soil AMF mycorrhizal inoculum potential (MIP), in control plots and plots that had second-year garlic mustard removed annually for the past five years (2005-2009). Removal treatment plots had significantly (P = 0.0240, df = 28) greater MIP than control plots (25.72±2.26% and 18.29±2.04%, respectively). MIP was negatively correlated with cover of garlic mustard (r 2 = 0.1325, P < 0.05, df = 30), which accounted for 13.2% of the variation in MIP. Cover of native vegetation in removal treatment plots (104.50±2.6%) was greater than that of the control plots (95.14±3.66%), (P = 0.0236, df = 115). These results show that removal of garlic mustard results in an increase in soil MIP and cover of native species; however, there is not a complete loss of MIP associated with garlic mustard invasion. Following removal of garlic mustard, our data suggest that mycorrhizal plants recover more slowly than non-mycorrhizal species, apparently due to a delay in the establishment of a well-functioning mycorrhizal association. Our study is the first to demonstrate that the MIP of native soils and cover of native species increase following reduction in the cover of garlic mustard.

Colonization and Effects of Garlic Mustard (Alliaria petiolata), European Buckthorn (Rhamnus cathartica), and Bell's Honeysuckle (Lonicera × bella) on Understory Plants After Five Decades in Southern Wisconsin Forests

“…Alliaria petiolata, for example, suppresses the growth rates of native tree seedlings by interfering with root infection by arbuscular mycorrhizal fungi (Stinson et al 2006). Alliaria petiolata appears to depress mycorrhizal inoculum potential (Anderson et al 2010;Roberts and Anderson 2001), and it been shown to inhibit seed germination and plant growth (Prati and Bossdorf 2004). Manipulative studies based on the removal of A. petiolata revealed an increase in evenness and ShannonWeiner diversity of forest understory plants (McCarthy 1997;Stinson et al 2007).…”

Low allelochemical concentrations detected in garlic mustard-invaded forest soils inhibit fungal growth and AMF spore germination

“…Disruption of the AMF over multiple growing seasons could have severe impacts on the growth of native herbs, as some native perennials are incapable of maintaining a positive phosphorus budget without their associated AMF (Merryweather and Fitter 1995). However, recent work by Anderson et al (2010) demonstrates that the suppression of AMF can be reversed when garlic mustard is removed for multiple consecutive growing seasons. Sites invaded by garlic mustard may require long-term and intense management to prevent an overall reduction in the abundance of the forest fungal community.…”

Mycorrhizae, invasions, and the temporal dynamics of mutualism disruption

“…These changes to the abiotic and biotic soil environment may persist as legacy effects. The temporal dynamics of belowground legacy effects following invader removal are poorly understood (but see Anderson et al 2010 andLankau 2011), but inferences can be drawn based on current understanding of the biology of mycorrhizal fungi.…”