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

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 (A_tot) 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, T_dir and T_tot.