Change of Spatial Structure Characteristics of the Forest in Oshiba Forest Park in 10 years
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Traditional parameters of forest structure could not meet the need of modern forest management completely. In order to know change law of forest structure in a given period, based on the survey on forest status, spatial structure characteristics of the forest dominated by Pinus densiflora and Chamaecyparis obtusa in 1999 and 2009 were studied by four spatial structure indices of mingling, angle index, neighborhood comparison and opening degree. The results indicated that: Species richness increased somewhat with seven species in 2009 while four species in 1999. The diameter class of Pinus densiflora was not continuous due to lack of small trees, whereas other species were small trees except for Chamaecyparis obtusa. The average mingling was 0.316 and 0.567 respectively in 1999 and 2009, indicating that mixed degree between species from middle-mixed developed into high-mixed level. The distribution pattern of all trees from regular became random. However, neighborhood comparison was 0.456 and 0.474 respectively in the two periods, showing the ratio of the trees whose growth was in oppressed status increased somewhat. And the average opening degree decreased from 0.393 to 0.304, indicated that growth space of most trees were in inadequate condition in 2009. From succession, Pinus densiflora will disappear from the stand finally, while Chamaecyparis obtusa will continue to be in dominance in competition between species. Most of broad-leaved species are in disadvantage at present, and effective measures need to take to protect successful growth of them. Finally, possible operation plan for the forest was discussed.