Impact of Invasion of Bursaphelenchus xylophilus on Species Diversity of Pinus massoniana Forests

The invasion of the pine wood nematode (Bursaphelenchus xylophlius) has a significant impact on the biodiversity and ecosystem function of Pinus massoniana forests. In this paper, P. massoniana forests infected by pine wood nematode for 4 (4Y) and 8 years (8Y) were selected as study subjects, and compared with uninfected P. massoniana forests (UN) and evergreen broad-leaved forests (EV). Three permanent sample plots of 30 m×30 m were set up in four community types in Suichang County, Zhejiang Province in 2020, to study the changes of community structure and succession characteristics caused by the invasion of P. massoniana by B. xylophilus. The results showed that the ratio of 8Y broad-leaved tree species was second only to EV; the diameter distribution of the four communities was dominated by small-diameter classes, and the proportion of broad-leaved trees in woody plants with DBH≥1cm was UN(64.99%), 4Y(66.61%), 8Y(90.64%) and EV(98.83%), respectively; the species richness, Shannon-Wiener index and Simpson index of the four communities were ordered by EV > 8Y > UN > 4Y, and the variation trend of tree species diversity was consistent with that of woody plants with DBH≥1cm, while the diversity index of shrub species remained low after infection. The Jaccard similarity coefficients of different communities were 0.349 for 4Y-UN, 0.316 for 8Y-UN, 0.258 for EV-UN, 0.232 for 4Y-EV, 0.263 for 8Y-EV. The results showed that the species composition of P. massoniana forest changed significantly after the invasion of pine wood nematode, and the invasion of pine wood nematode accelerated the succession of zonal vegetation (evergreen broad-leaved forests).