Natural Rehabilitation Of Woody Species On Cut Slash With Pine Wood Nematode Disease

After a dozen years of natural recovery, the pine wilt nematodes damaging forestlands in Zhoushan Island had been through a community succession from pure forest stands made up of black pines or masson pines to many kinds of complex forest stand types. Those transforms of the woody species composition in forest stand closely related with the environmental factors.Using Two-way Indicator Species Analysis (TWINSPAN) and Canonical Correlation Analysis (CCA),forest stands after succession in Zhoushan were classified by quantities. Typical succession types were explained by the environmental factors. Conclusions are as following:(1) After a dozen years of natural recovery, the former pine wood forest stands had been transformed into7types of forest stands. The factors:soil depth, humus depth, soil pH values, aspect, slope position, bare rock rate and distance from seaside significantly related with the species distribution pattern. According to the CCA orders, the key succession driven factors in different succession types were indicated. In response to these findings, different reform measures and proposals were raised accommodating to different secondary forest stand types.(2) Invasions of pine wood nematodes enriched the structural hierarchies of woody plants in pine stand communities. Proportions of broadleaf trees in the communities significantly increased. However, diameter class analysis showed that this transform was still in primary stage of the succession. Trees in the stands were still in middle and young periods. White oak was the only tree species showed stable diameter structure in the succession process.(3) Investigations of10secondary pine tree stands showed that secondary pine trees were still infested by pine wood nematodes in Zhoushan Islands. The harm degree was relatively small, with the incidence between0and5%. Comparing to masson pines, black pines were damaged much more seriously.These results indicated that natural recovery of pine communities with different geographical environment, different stand origins and different harm degree showed different directivities. We could thus make artificial tending and optimization, keeping ecological function and landscape of the local forest stands, also avoiding secondary pine wood nematode destruction to pine forests.