Mechanisms of negative interference of invasive earthworms on AMF communities involve direct consumption of AMF hyphae or fine roots colonized by AMF (Bonkowski et al. 2000), increased physical disturbance through burrowing actions (Gange and Brown 2002), increased nutrient availability in the soil (see McLean et al. 2006) and decrease soil organic matters (Frelich et al. 2006). Direct consumption of hyphae and physical disturbances may disrupt the contact of external hyphae with AMF-dependent or other host plants and can substantially decrease the AMF biomass (Gormsen et al. 2004). This will have a direct negative effects on nutrient (P and N) supply to AMF-dependent host plants and carbon flow from host plant to AMF.
Lawrence et al. (2003) …show more content…
(2007) suggested that the changes in mycorrhizal communities, including decreased root colonization of AMF-dependent plants likely contributed to changes in plant community structure and diversity in hardwood forests. We suggest that the loss of understory herbaceous and woody plant communities and dominance of non-mycorrhizal Carex pensylvanica in the understory of North American hardwood forests may be driven by loss of AMF from forest soils due to earthworm invasions. In addition, invasive earthworms not only favor dominance of hardy native sedges but also indirectly favor the dominance of invasive plants, which are either non-mycorrhizal or non-obligate mycorrhizal, by increasing the nitrogen (N) level in the soil (Nuzzo et al. 2009). Clause et al. (in review) showed a strong correlation between standing exotic vegetation and earthworm population in some of the disturbed grassland sites in central California. A negative correlation between invasive Lumbricus rubellus and endangered fern, Botrychium mormo have also been reported in Illinois (USA) urban woodland (Gundale 2002). The possible mechanism suggested include mechanical damage of AMF, necessary for Botrychium mormo to obtain nutrients, as a consequence of mixing of soil horizons. In a recent study in historically earthworm free San Clemente Island, CA, we found a significant positive relation between percent invasive grass cover and presence of invasive earthworm, …show more content…
2004; Bardgett et al. 2005; Bardgett and Wardle 2010), there is lack of enough information to show the directions of interactions between invasive earthworms and AMF, and the impact of interactions on plant communities. Although, interactions could be positive, negative, and neutral (e.g., Wurst et al. 2004), the available examples point at increasing negative effects of invasive earthworms on plant community, particularly in previously earthworm free regions. Given the far-reaching importance of AMF for plant nutrient (Smith and Smith 2010), we suggest that earthworm invasions alter AMF community, which can have ramification for the functioning of ecosystems. Studies have also shown that the changes in AMF abundance and diversity due to disturbance can have a profound effects on plant community structure, diversity (Stampe and Daehler 2003), as well as the functionality and stability of ecosystems (van der Heijden et al.
Lawrence et al. (2003) …show more content…
(2007) suggested that the changes in mycorrhizal communities, including decreased root colonization of AMF-dependent plants likely contributed to changes in plant community structure and diversity in hardwood forests. We suggest that the loss of understory herbaceous and woody plant communities and dominance of non-mycorrhizal Carex pensylvanica in the understory of North American hardwood forests may be driven by loss of AMF from forest soils due to earthworm invasions. In addition, invasive earthworms not only favor dominance of hardy native sedges but also indirectly favor the dominance of invasive plants, which are either non-mycorrhizal or non-obligate mycorrhizal, by increasing the nitrogen (N) level in the soil (Nuzzo et al. 2009). Clause et al. (in review) showed a strong correlation between standing exotic vegetation and earthworm population in some of the disturbed grassland sites in central California. A negative correlation between invasive Lumbricus rubellus and endangered fern, Botrychium mormo have also been reported in Illinois (USA) urban woodland (Gundale 2002). The possible mechanism suggested include mechanical damage of AMF, necessary for Botrychium mormo to obtain nutrients, as a consequence of mixing of soil horizons. In a recent study in historically earthworm free San Clemente Island, CA, we found a significant positive relation between percent invasive grass cover and presence of invasive earthworm, …show more content…
2004; Bardgett et al. 2005; Bardgett and Wardle 2010), there is lack of enough information to show the directions of interactions between invasive earthworms and AMF, and the impact of interactions on plant communities. Although, interactions could be positive, negative, and neutral (e.g., Wurst et al. 2004), the available examples point at increasing negative effects of invasive earthworms on plant community, particularly in previously earthworm free regions. Given the far-reaching importance of AMF for plant nutrient (Smith and Smith 2010), we suggest that earthworm invasions alter AMF community, which can have ramification for the functioning of ecosystems. Studies have also shown that the changes in AMF abundance and diversity due to disturbance can have a profound effects on plant community structure, diversity (Stampe and Daehler 2003), as well as the functionality and stability of ecosystems (van der Heijden et al.