• The ectomycorrhizal fungal community composition/structure is related to biochemical diversity and characteristics of host pines
  
  
• Microbial community structure is related to biochemical diversity of associated pines
  
  
• Decomposition processes in the bulk soil and rhizosphere of trees vary with phytochemistry of local dominant individual pines and whether terpenes and phenolics have direct effects on these soil biological parameters

We will also examine:

• The relationship between functional and taxonomic diversity of mycorrhizas

Different mycorrhizal species may preferentially form associations with different individual plants, if the attributes of the plants offer different micro-environments. Likewise, the mycorrhizas themselves can affect the performance of plants via chemical/ecological interactions at the soil-plant interface. Plant–mycorrhizal associations are an often neglected, but nevertheless key link in the functioning of ecosystems and are important to Scots pine (Jonsson et al., 1999). Previously, assessing the diversity of mycorrhizal species has been hampered due to a lack of taxonomic expertise, and the difficulties of relating surface fruiting bodies with below ground hyphae and root associations. However, recent developments in molecular genetics now offer methodological approaches for the investigation of mycorrhizal species diversity in relation to higher-plant diversity, using fungal specific primers and sequence based molecular identification (Gardes & Bruns, 1993; Bruns et al., 1998). Molecular techniques are also being employed to identify to which individual tree a particular root, and associated mycorrhizas, belongs.

Biochemical variation in secondary metabolites may have their most profound effects at the ecosystem level via direct and indirect effects on soil microbial diversity and the processes they are responsible for (Wardle, 1998). Phenolics may alter the availability of organic nutrients and so exert control over decomposition processes (Northrup et al., 1995). Both phenolic compounds and terpenes can be potentially inhibitory to microorganisms and are known to be specifically toxic to specialist groups e.g. methanotrophs and nitrifiers (Knowles, 2000). Organic-N complexed with phenolics can be accessed by the host plants mycorrhizal symbionts (Bending & Read, 1996) such that nutrients may bypass the normal microbially-mediated decomposition cycle. These interactions between the biochemical variation in plant litter inputs and the mycorrhizas of the host plant may explain the dominance of phenolic-rich plant communities in such ecosystems (Chapin, 1995) and hence it is important that interactions between mycorrhizas and the saprophytic microbial community are examined at the same time.

Contact: Colin Campbell