关帝山云杉次生林空间结构对林内光环境的影响

Effects of spatial structure of Picea asperata secondary forest on light environment in Guandi Mountain of northern China

【目的】探究关帝山云杉次生林林分的空间结构对林内光照的影响,为了解森林内部光环境的特点及影响因素提供数据支持和理论参考。【方法】以庞泉沟国家自然保护区4 hm^(2)固定样地为研究对象,将样地划分为100块20 m×20 m的小样方,在2021年7—8月间,测量样方内活立木(DBH≥1 cm)的相对坐标和胸径,利用半球摄影法获取半球面林冠影像,分析得到林内光环境参数,研究样地空间结构特征和光分布特征,并对林分空间结构与林内光环境间的相关关系进行验证。【结果】(1)林冠开度(CO)和林下光照主要表现为边缘小于内部,叶面积指数(LAI)表现为边缘大于内部。林上总光照(Atot)值整体较大,各区域间差异较大,仅有13.7%的光照可以从森林上部进入到林下。(2)林木分布格局主要表现为团状分布,大小分化程度为亚优势-中庸、中庸和中庸-劣态3种状态,树种混交度为零弱度混交、中弱度混交和中强度混交3类。(3)树种的水平分布格局和CO呈显著正相关(P<0.05),空间隔离程度和LAI呈显著正相关(P<0.05),和林下直射光(T_(dir))、林下总光照(T_(tot))呈显著负相关(P<0.05)。【结论】林内光照和林分空间结构之间表现出一定的相关关系,林木的水平分布格局主要影响CO,树种间的混交程度主要影响LAI、Tdir和Ttot。

[Objective]This paper aims to explore the influence of spatial structure of Picea asperata secondary forest on lighting in the forest,and to provide data support and theoretical reference for understanding the characteristics and influencing factors of the light environment in the forest.[Method]Taking the 4 ha fixed sample plot in Pangquangou National Nature Reserve of Shanxi Province of northern China as the research object,the sample plot was divided into 100 blocks of 20 m×20 m small quadrat.Between July and August of 2021,the relative coordinates and DBH of the living trees(DBH≥1 cm)in the small sample plot were measured,and the hemispherical canopy images were obtained by hemispherical photography.The light environment parameters in the forest were analyzed and obtained,the spatial structure characteristics and light distribution characteristics of the sample plot were studied,and the correlation between the spatial structure of the forest and the light environment in the forest was verified.[Result](1)The canopy opening(CO)and the light under the forest mainly showed that the edge was smaller than the interior,and the leaf area index(LAI)showed that the edge was larger than the interior.The total light(Atot)value on the forest was large as a whole,and there was a large difference among regions.Only 13.7%of the light can enter from the upper part of the forest to the lower part of the forest.(2)The distribution pattern of forest trees was mainly characterized by cluster distribution.The degree of size differentiation was sub superiority-moderate,moderate and moderate-inferior.The mixed degree of tree species was zero-weak,medium-weak and medium-intensity.(3)The horizontal distribution pattern of tree species was significantly positively correlated with CO(P<0.05),the spatial isolation degree was significantly positively correlated with LAI(P<0.05),and was significantly negatively correlated with direct sunlight(T_(dir))and total sunlight(T_(tot))under the forest(P<0.05).[Conclusion]There is a certain correlation between the light in the forest and the spatial structure of the forest.The horizontal distribution pattern of trees mainly affects CO,and the mixing degree among tree species mainly affects LAI,Tdir and Ttot.