Characteristics of typical Masson pine community and soil properties at the early invasive stage of pine wood nematode in the Three Gorges Reservoir Region, central China.

In recent years, the invasion of the pine wood nematode (Bursaphelenchus xylophilus) has caused severe damage to Masson pines in the Three Gorges Reservoir Region, threatening pine forests in the region and ecological security in the Three Gorges water conservation project. Five sites of uniform Masson pine (Pinus massoniana) forests with various infection periods over time (non-infected, infected at two year intervals between 1 and 7 years) of pine wilt disease were selected for quadrat sampling and inspection of individual trees at each site. We investigated plant community structures and dynamic changes of physical and chemical properties in the soil of Masson pine stands. We recorded a total of 37 tree species ( DBH≥2.0 cm) in 30 families and 33 genera in 15 plots, where Masson pine was the dominant species with an importance value IV=49.63% and broadleaved trees, such as camphor (Cinnamomum camphora), oriental white oak (Quercus aliena), cork oak (Q. variabilis) and China loropetal (Loropetalum chinense) as subdominant species. Compared with pine stands at non-infected sites, those at infected sites showed a sharp reduction in the number of trees, but with an obvious increase in their mean DBH and mean height. The invasion of pine wood nematode had a large impact on species diversity at various spatial structures of trees, shrubs and herbs. The pattern of variation in species diversity indices over the infection periods followed the theory of the “mid-altitude bulge. No significant differences were observed in chemical properties of the soil at the various infection sites. However, water-related physical properties in the soil were significantly different among the pine stands. This study revealed the plant community structures, indices of species diversity and dynamic changes of soil physical and chemical properties in the soil of Masson pine communities at the early stages of invasion by pine wilt nematodes in the region. This may provide basic evidence for the ecological security in the region by transforming the simple Masson pine structure with other species and thus increasing the health of plant communities in the region.