Forest management effects on the ectomycorrhizal macromycete community in tropical montane forests in Mexico

While forest management impacts the ectomycorrhizal fungi (EMF) community, most of the evidence regarding such effects has been obtained from temperate forests of the Northern Hemisphere and little is known of their prevalence in highly diverse tropical habitats. This study analyzes the responses of the EMF community in managed tropical montane forests in the southern Mexican state of Chiapas. EMF community composition and diversity were evaluated over a 2-year period along a gradient of structural and microclimatic conditions of the forest associated with the stages of a cycle of silvicultural practices (R = release cutting, T = thinning, and F = final regeneration cutting), as well as in a mid-successional unmanaged forest (UF) as a reference system. The silvicultural practices involve varying intensities of tree harvesting (approximate to 20% in T to approximate to 80% in F). It is hypothesized that: (1) diversity and composition of EMF communities are influenced by changes in forest conditions, prin-cipally as a result of canopy cover alteration due to forest management, and (2) late forest successional condi-tions are associated to more diverse EMF communities, while more intensive silvicultural practices reduce their diversity. A total of 75 EMF species were recorded. Diversity analysis using Hill numbers showed a close rela-tionship between diversity and forest conditions: total species richness, D-0 = 5.7 +/- 0.6 in F up to 11.7 +/- 1.3 in UF; richness of abundant species, D-1 = 4.1 +/- 0.4 in F up to 7.5 +/- 0.4 in UF; richness of very abundant species D-2 = 3.3 +/- 0.3 in R up to 5.5 +/- 0.3 in UF. Canopy cover (9.8 +/- 4% in F and 80.6 +/- 5% in UF) was the main factor affecting EMF diversity, mainly due to its influence on herbaceous cover, tree species richness (path analysis, R-2 = 0.32; p < 0.05), and microclimatic variables. Turnover of the most abundant EMF species from the most intensive management practice towards the later successional forest conditions was observed. Late successional conditions allow for maintenance of more diverse EMF communities, while more intensive practices reduce their diversity (p < 0.05, in both cases). Rare fungal species appear to be more vulnerable to highly intensive man-agement, and account for most of the EMF diversity in UF. The results indicate the importance of preserving relatively undisturbed species-rich forest stands near intensively managed stands in order to maintain biological integrity of the EMF community and ecosystem functioning in tropical montane forests.