Ectomycorrhizal (EM) fungi from Pinus yunnanensis forests, a dominant vegetation type in central Yunnan and adjacent regions, were sampled from 2000-2005. A total of 834 mushroom collections representing 211 taxa in 39 genera and 27 families were obtained and identified. Of these, Russula, Boletus, Lactarius, Suillus, Tricholoma, Cantharellus and Thelephora were the dominant genera. Our ecological surveys indicate that EM fungal fruiting and distribution patterns are strongly affected by climate (e.g., air temperature and precipitation), vegetation (e.g., stand age, crown density and herbaceous vegetation), soil conditions (e.g., pH, litter and humus layers), topographic features (e.g., altitude, position and steepness of slopes), and human disturbance (e.g., commercial harvesting, logging, fire and residue removal).
The 4 primary findings were: (1) There was a consistent seasonal variation in the number of EM fungi associated with Pinus yunnanensis. Over the 5-year period, the lowest numbers of EM fungi were found during the winter months of January, February, and March. This number rose rapidly during the spring and peaked in mid and late summer. (2) The abundance, composition, and richness of EM fungi significantly increased with increasing altitude between 1500-2100 m, and then slightly decreased up to 2500 m. Usually a species was found only within a particular range of altitudes. (3) EM fungal richness increases as the host matures. The tendency is to find greater numbers of EM species associated with older Pinus yunnanensis stands. This increase in EM fungi with maturing of host stands may be related to changes in available photosynthate, root exudates and soil conditions. (4) Human disturbance has a major negative impact on EM fungi species richness, abundance, and community composition. Large-scale harvesting directly affected the production of fruit bodies, either by damaging or exhausting mycelia, shifting competitive relations with other species, or by causing reproductive failure due to decreased spore production. EM fungi richness declined with increased fire severity and logging intensity. Both litter and humus layers and grass density appeared to affect sporocarp production with litter depth and EM fungi sporocarp abundance being negatively correlated. Sporocarps of EM fungi were scarce in Pinus yunnanensis stands dominated by the grass Eupatorium adenophorum.