Arbuscular Mycorrhizas in Plant Communities

Diversity and classification of mycorrhizal associations

“…Reports of growth depression caused by VAM fungi are surprisingly rare considering how ubiquitous these associations are, and seem to be even rarer for other types of mycorrhizas. For example, significant growth depression did not occur in any of the VAM inoculation trials using natural soil fertility levels summarised in Table 6 of Brundrett & Abbott (2002): These data were from 23 studies of plants from 11 natural ecosystems in which 63% of 235 plant species were highly responsive to mycorrhizas and the rest did not respond significantly. Most plants with ECM are considered to be highly dependent on these associations, but some hosts (e.g.…”

“…Damage to non-host roots by ECM fungi has most often been reported in sterile culture experiments using hosts and fungi that do not normally associate together (Molina & Trappe, 1982 b). During succession in many habitats, NM plants are outcompeted by mycorrhizal species (Brundrett, 1991;Francis & Read, 1995 ;Brundrett & Abbott, 2002). This probably occurs because the mycorrhizal species are more efficient at acquiring limiting soil nutrients such as phosphorus (Newman, 1988 ;Brundrett, 1991), but direct antagonism of non-host plants by mycorrhizal fungi may also occur in some cases as inoculum levels increase during succession (Allen et al, 1989).…”

“…Hyphal mats formed by ECM fungi considerably alter the soil physical and chemical environment (Griffiths, Baham & Caldwell, 1994), perhaps creating inhospitable conditions for establishment of other plants. Interactions between plants with different types of mycorrhizas are discussed in detail elsewhere (Francis & Read, 1995;Brundrett & Abbott, 2002).…”

Is transplanting an effective means of preserving vegetation?

“…Although the stability and resilience of efficiently functioning terrestrial ecosystems are based on microbial diversity (Tiedje et al 1999, Fitter et al 2005, disturbances to soil systems often reduce diversity. Disruption of hyphal networks may produce species shifts in microbial soil communities (Haselwandter 1997;Caplan et al 1999;Brundrett and Abbott 2002); nearly half the normal ectotrophic mycorrhizal (EMF) morphotypes were lost from transplanted seedlings in one experiment (Jones et al 2003). Airborne inocula eventually enrich fungal communities in any site, but initial absence of necessary symbionts in a transplant location could prevent establishment of some plants (Richardson et al 2000).…”

“…Both arbuscular mycorrhizas (AMF) and EMF are sensitive to soil temperature, pH, drainage, aridity, organics, compaction, erosion, and other factors following topsoil removal Abbott 2002, Brundrett and, and mycorrhizal populations insufficiently tolerant to site changes produced by transplanting can be displaced by others more resilient (Caplan et al 1999;Diaz 2004). In addition, loss of normal soil fungi required by native vasculars could permit establishment of exotics with less specific mycorrhizal requirements (Stinson et al 2006).…”