Effects Of Bursaphelenchus Xylophilus Invasion On The Plant Community

Bursaphelenchus xylophilus is one of the harmful plant inspection and quarantine pests, which is vectored mainly by a beetle {Monochamus altematus). Once the pine tree is infected by Bursaphelenchus xylophilus, even a pine tree as old as tens of years will die in two to three months. The pine wilt disease does a destructive harm to ecosystem.Implicit in the chronosequence approach is the substitution of space for time, the plots were located in areas that had been infected after 0, 4, 8, 12 years, and with a mid-aged evergreen broad-leaved forest as comparison, we studied the effects of Bursaphelenchus xylophilus invasion on the plant community.1. Dynamics of forest structure and species composition after the infection of Bursaphelenchus xylophilusThe canopy layer of pine forests was composed of pine trees before the appearance of pine wilt disease and the disappearance of canopy pined affected the ecosystem drastically. Forest structure and species composition obviously changed and the relationship between H, DBH and coverage were different among all the communities (ANOVA, p<0.0001). It is concluded that the dominant species had changed from Pinus massoniana to Schima superba and Lithocarpus glaber because of the two species fast growing in the communities after the pine wilt disease. Twelve years after Bursaphelenchus xylophilus infection, the community can regenerate near their mother tree population2. Dynamics of plant population structure and spatial pattern ten main species population in successional communitiesP. massoniana population seems stable before the pine wilt disease; then main of the pine trees died. S. superba population showed a growing trend from 0 to 8 years old after Bursaphelenchus xylophilus infection, then tending to stable, and in the mid-aged evergreen broad-leaved forest, it showed a reverse J-shaped distribution. L. glaber individuals were rarely found before infection, in successional stages and mid-aged evergreen broad-leaved forest, it showed a growing trend. Quercus febri, Liquidambar formosana, Myrica rubra, Symplocos stellaris and Symplocos sumutia all showed a growing trend, but the Q. febri is absent in the mid-aged evergreen broad-leaved forest. Dalbergia hupeana showed a growing trend in 0 and 4 years old after infection, and most size absent in 8 and 12 ones, and completely absent in evergreen one, and Symplocos setchuensis is on the contrary.The populations were significantly clumped of most of the species population that thereare some others showed Possion, this may be explained by its seed dispersal characteristics and the stages of succession.3. Dynamics of plant functional groups after the infection ofBursaphelenchus xylophilusThe plant functional groups divided into four types: growth form, life form, fruit types and leaf characteristics based on morphologic, physiology and physics. We found that arbor, microphyll, simple leaf and evergreen plant dominated in all of the communities. In fruit type, drupe, berry and capsule dominate; entire leaf is little less than not-entire; and in life form, MaPh, MePh, MiPh and LPh are the most, but the differences between each other is little, and there's some differences in leaf character. The PFGs remains the high diversity in successional communities as in the evergreen one.4. Measures of forest managementSome expert and regional forest department raised some measures because of destruction of the pine wilt disease, but little related to ecology. Today, forest management took account of protection of biodiversity. Based on the successful regeneration to evergreen broad-leaved forest after the infection of the pine wood nematode in Xiangshan City, Zhejiang Province, we can say that forest management can be through natural regeneration, with some intervention to compensate the lack of intrinsic self-regulation.Conclusions of this thesis is that in species-rich pine forest, such as S. superba, L. glaber, L. formosana and S. sumuntia etc, with more light and nutrient, the evergreen broad-leaved species can establish and regenerate in the community, the dominant species change from pine to evergreen broad-leaved types directly after pine wilt disease. We supported that the pine wilt disease is an acceleration factor of succession from pine forest to evergreen broad-leaved forest.