Estructura, dinámica y función de las comunidades de hongos ectomicorrícicos asociadas a plantaciones forestales bajo distintos tipos de gestión silvícola y micológica

Resumen

Ectomycorrhizal fungal communities represent a significant fraction of forest ecosystems, being directly involved in trees’ growth and cycling of nutrients. In addition, the wild production and cultivation of edible ectomycorrhizal fungi have a social and economic importance. The main objective of this thesis was to study the structure, seasonal dynamics and function of ectomycorrhizal fungal communities. Ectomycorrhizal community structure and its dynamics was studied for both ectomycorrhizas and soil mycelium, combining morphological identification of ectomycorrhizas and New Generation Sequencing techniques (PacBio sequencing) for the analyses of soil mycelium communities. Furthermore, species-specific mycelium quantification was performed by Real-Time PCR. The functionality of ectomycorrhizal communities was studied through acid phosphatase and leucin aminopeptidase determinations by enzyme fluorometric assays. Three different experiments were performed. In the first one, the effects of silvicultural practices (clear-cut and partial cut treatments) on the soil mycelium community and ectomycorrhizal structure were studied in a Pinus sylvestris managed forest. We have found that cutting treatments produced a variation on soil fungal community composition one year after cutting, reflecting the changes of functional organization of the fungal community with a decrease of the relative abundance of ectomycorrhizal fungi and increase of moulds. Cutting effects were also evident on the ectomycorrhizas with a decrease of root tips density and species richness. The changes in the ectomycorrhizal community structure were also studied on different age classes stands. No differences in species richness and root tips density were observed between age classes, but there were differences at community structure level, with an overall increase of russuloid species in the older age classes. In the second experiment, the seasonal dynamics of black truffle Tuber melanosporum mycelium and ectomycorrhizas were studied in a 16 year-old holm oak plantation, with both productive and non-productive trees. We found that extraradical mycelium biomass varied seasonally and between two consecutive years, and was correlated with the precipitation that occurred one month before sampling. Moreover, truffle mycelium biomass and ectomycorrhizal tips were significantly correlated and more abundant in productive trees. Finally, differences in ectomycorrhizal community composition were observed between productive and non-productive trees, with lower T. melanosporum abundance and higher T. aestivum abundance in non-productive trees. In the third experiment, the ectomycorrhizal community functional responses on three hosts differing in the number and type of symbiotic associations (Acacia: ectomycorrhizas, arbuscular mycorrhizas and N-fixing bacteria; Eucalyptus: ectomycorrhizas and arbuscular mycorrhizas, and Pinus: ectomycorrhizas) were studied. Functional responses were measured by determining differential enzymatic potential to acquire organic phosphorous (P) and nitrogen (N). Differences in ectomycorrhizal community composition were detected among hosts. The potential N and P acquisition abilities were higher in those hosts with co-presence of rhizobial bacteria and/or arbuscular mycorrhizas, allowing us to support the importance of the host in the selection of the ectomycorrhizal composition.