| Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, an important invasive alien species of forestry in China, has been one of the most destructive forest diseases. Based on the research objectives in this paper of 11 pine forest in different forest types and different damage degree after the invasion of pine wood nematode in Fuyang and Zhoushan county, Zhejiang province, the impact of Pine Wood Nematode (PWN) and removal disturbance on the structure and function of pine forest ecosystem were analyzed. In three perspectives of pine tree population, plant community and pine forest ecosystem, the resistance ability to the invasion of PWN in different pine forest ecosystem were studied. Furthermore, the resistance and resilience mechanism of pine ecosystem invaded by pine wood nematode was also discussed. Through research, the main 5 results are as follows.1. In the aspect of plant diversity and niche, the change of plant community's structure caused by the invasion of PWN was studied. The result showed that when invaded by PWN, the Masson pine forest would suffer from some sort of disastrous damage, which made the supply of food resource for the PWN in forest insufficient. On that condition, if the formed community after resilience tend to be broad-leaved forest or mixture of Masson pine (Pinus masssoniana) and tree species of broad niche (Quercus fabric, Ilexpurpurea etc broad-leaved trees). Masson pine wouldn't dominate any more, and the species diversity in the forest would increase, On the contrary, if the formed community after resilience succeeded conversely to become the second generation's young Masson pine forest, the species diversity in the forest would decline.2. The "Index of Disturbing Intensity of Stump and Fallen Woods" (IDISF) created to represent the degree of disturbance of tree removal to plant diversity. When it comes to a specified harmed stand, the species diversity obeyed the principle of "Mid-altitude bulge" as the change of IDISF. Specifically, both excessive and insufficient removal of infected trees will cause decline of plant species diversity in certain degree. Covariance analysis of IDISF indicated that different IDISF had no significant effects on the species diversity of the arbor layer, but had different impacts on that of the shrub and herb layers, and therefore,it can be used to assess changes in species diversity of different Masson pine communities after the invasion of pine wood nematode.3. From the view of growth increment, biomass dynamics and timber outturn, the change of plant community's function caused by the invasion of PWN was studied. The result showed: under the disturbance of removal of infected trees and attractant, special stand's average growth level achieved a climax. Moreover, if the average growth increment of unattacked Masson pine in the infected forest stand was to be maintained, a series of protecting measures must be taken.A series of grey forecasting models and grey-markov models were also established. The result showed: the predictive precision of the built grey forecasting model is good by using the post-test residue ratio C and minimum error probability P, and the history matching average relative error of the forecasting model combination of grey-markov is 4.89%. So these models all have a good simulation accuracy, which can be utilized in growth prediction of both infected and normal Masson pine forest factors.4. Based on intensive observation, in three perspectives of pine tree population, plant community and pine forest ecosystem, the resistance ability in different DBH class of pine host, different pine structure, different host species, different distributing pattern of dominant tree species, and different species diversity of herb and shrub layers in the forest were studied. The result showed: as for pine tree population, most infected pines are less DBH class in the forest. The greater mean crown width, the percentage of bole with crown of tree and 5-year growth increment, the higher the resin category, the bigger resistance ability of pine tr... |
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