Diversity and composition of ectomycorrhizal community on seedling roots: the role of host preference and soil origin.

As the main source of inocula, ectomycorrhizal (ECM) fungal propagules are critical for root colonization and seedling survival in deforested areas. It is essential to know factors that may affect the diversity and composition of ECM fungal community on roots of seedlings planted in deforest areas during reforestation. We quantitatively evaluated the effect of host plant and soil origin on ECM fungal propagule community structure established on roots of Castanopsis fargesii, Lithocarpus harlandii, Pinus armandii, and Pinus massoniana growing in soils from local natural forests and from sites deforested by clear-cut logging in the 1950s and 1960s. ECM root tips were sampled in April, July, and October of 2006, and ECM fungal communities were determined using ECM root morphotyping, internal transcribed spacer (ITS)-RFLP, and ITS sequencing. A total of 36 ECM fungal species were observed in our study, and species richness varied with host species and soil origin. Decreased colonization rates were found in all host species except for L. harlandii, and reduced species richness was found in all host species except for P. armandii in soil from the deforested site, which implied the great changes in ECM fungal community composition. Our results showed that 33.3% variance in ECM fungal community composition could be explained by host plant species and 4.6% by soil origin. Results of indicator species analysis demonstrated that 14 out of 19 common ECM fungal species showed significant preference to host plant species, suggesting that the host preference of ECM fungi was one of the most important mechanisms in structuring ECM fungal community. Accordingly, the host plant species should be taken into account in the reforestation of deforested areas due to the strong and commonly existed host preference of ECM fungi.

A molecular approach to species identification of Chenopodiaceae pollen grains in surface soil.

Pollen identification and classification are important not only for palynologists, but also for systematists and ecologists. Because palynological methods for the identification of pollen in surface soil until now could resolve at best to the generic level, we have developed a molecular approach to species-level identification of Chenopodiaceae pollen in surface soils. Surface soil samples were collected in the central area of Junggar Desert Basin, Xinjiang, China. Fresh leaves of 19 Chenopodiaceae species were sampled for DNA sequencing, establishing a database of internal transcribed spacer (ITS) regions of nuclear ribosomal DNA for Chenopodiaceae. Individual chenopod pollen grains in a soil sample were separated from the soil and the ITS1 region of each pollen grain was amplified using nested PCR and sequenced. By comparing the amplified ITS1 sequences to those in the Chenopodiaceous database, we identified the pollen in the soil samples to the level of species. The new method provides a technical reference for species identification of soil surface pollen for other families. This work is necessary for further efforts to interpret the relationship of surface soil pollen to vegetation characteristics. It also has significant potential for enhancing the ability to identify pollen in clinical airborne allergen or criminological studies.