采伐强度对水源涵养林林分结构特征的影响

Effect of the Cutting Intensity on Structural Characteristics of Water Conservation Forest

水源涵养林一般要求具有复层、冠长率高、冠幅完满、树种混交、灌草丰富的森林结构。中村林场位于山西省晋城市沁水县中村镇,其经营范围位于黄河中游一、二级支流的上游山区地带,90%以上为水源涵养林,油松为主要优势树种。为增强林分水源涵养能力,林场开始采取近自然经营理念与技术优化林分结构,增强生态功能,但由于生态公益林采伐限额的限制,林场在小面积范围内进行了不同采伐强度的经营试验。本研究定量分析了3种经营强度下形成的3种林分类型(包括不经营的高密度油松纯林T_0、总间伐强度47%的油松相对纯林T_1、总间伐强度62%的油松混交林T_2)的空间结构与非空间结构,包括空间混交度、大小比、多样性指数、林层结构、径阶分布、林冠层指标(冠长率、冠幅面积与冠幅)、灌草盖度等,并初步提出未来近自然经营措施。结果表明:T_2林分各林层树种丰富度、冠长率与冠幅面积最高,其次是T_1,T_0最差;在林分水平结构与林分多样性以及树种竞争力方面,亦是同样结果;由此可知,人工生态公益林其森林结构与生态功能只有通过经营才能得到提高。对于初始密度高的人工水源涵养林,只有通过不断间伐,调整林分密度与林木分布,才能促进天然更新,增加树种多样性与提高林分稳定性。本研究为全场调整林分结构和制定针对性经营措施提供数据支持与基本林分特征参数,同时,为被划分为生态公益林的高密度人工林经营提供案例参考。

It is required for water conservation forests to have forest structures of a multilayer, high crown length, fullness crown,species mixed, rich shrub and grass. Zhongcun Forest Farm is located in Zhongcun Township,Qinshui County,Jincheng City, Shanxi Province. The forests in this farm are within the upstream mountaineous area of the first/second grade tributaries of the middle reaches of the Yellow River. More than 90% forests belong to water conservation type. Chinese pine is the dominant species. In order to enhance the conservation ability, the farm has began to take close-to-nature forest management philosophy and technology to optimize the stand structure to enhance the ecological function. However, due to limita- tions of ecological forest logging quota, cutting experiments only conducted within small forest area. Conse- quently, this paper quantitatively analyzed the spatial and non-spatial structure of three forest type with three cutting intensity （including non-managed high density pure Chinese pine forest To, relatively pure Chinese pine forest with total thinning intensity 47% T1 ,Chinese pine mixed forest with total thinning in- tensity 6 2 % T2 ）, including space mingling, size ratio, diversity index, layer structure, diameter distribution, canopy indicators （crown length ratio,crown area and crown length）, shrub and grass cover,etc. ,and ini- tially proposed future close-to-nature management measures. The results showed that T2 was the best in terms of layer species richness,crown length ratio and crown area, the second was T1, the worst was To, The similar results were obtained in terms of stand horizontal structure, species diversity and competitive- ness. Thus it could be seen the forest structure and ecological function of artificial ecological forest could be enhanced only by management, for artificial water conservation forest with high density, only through con- tinuous thinning to adjust stand density and trees distribution,consequently,to promote natural regenera- tion,increase diversity and improve forest stability. This study would provide data support and basic stand characteristic parameters for structure adjustment and specific management measures in region of whole forest farm, as well as to provide management case reference for artificial forest classified as ecological forest.