Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), Collaborative Innovation Center for Mountain Ecology & Agro-Bioengineering (CICMEAB), College of Life Sciences, Guizhou University, Guiyang, Guizhou Province, China.
PeerJ. 2024 Mar 15;12:e17067. doi: 10.7717/peerj.17067. eCollection 2024.
Canopy structure and understory light have important effects on forest productivity and the growth and distribution of the understory. However, the effects of stand composition and season on canopy structure and understory light environment (ULE) in the subtropical mountain forest system are poorly understood. In this study, the natural secondary - mixed forest (MF) and plantation forest (PF) were investigated. The study utilized Gap Light Analyzer 2.0 software to process photographs, extracting two key canopy parameters, canopy openness (CO) and leaf area index (LAI). Additionally, data on the transmitted direct (Tdir), diffuse (Tdif), and total (Ttot) radiation in the light environment were obtained. Seasonal variations in canopy structure, the ULE, and spatial heterogeneity were analyzed in the two forest stands. The results showed highly significant ( < 0.01) differences in canopy structure and ULE indices among different forest types and seasons. CO and ULE indices (Tdir, Tdif, and Ttot) were significantly lower in the MF than in the PF, while LAI was notably higher in the MF than in the PF. CO was lower in summer than in winter, and both LAI and ULE indices were markedly higher in summer than in winter. In addition, canopy structure and ULE indices varied significantly among different types of stands. The LAI heterogeneity was lower in the MF than in the PF, and Tdir heterogeneity was higher in summer than in winter. Meanwhile, canopy structure and ULE indices were predominantly influenced by structural factors, with spatial correlations at the 10 m scale. Our results revealed that forest type and season were important factors affecting canopy structure, ULE characteristics, and heterogeneity of forests in subtropical mountains.
林冠结构和林下光照对森林生产力以及林下植物的生长和分布具有重要影响。然而，林分组成和季节对亚热带山地森林系统林冠结构和林下光照环境（ULE）的影响仍知之甚少。本研究以天然次生-混交林（MF）和人工林（PF）为研究对象。利用 Gap Light Analyzer 2.0 软件处理照片，提取了两个关键的林冠参数：林冠开度（CO）和叶面积指数（LAI）。此外，还获得了光照环境中直射（Tdir）、漫射（Tdif）和总（Ttot）辐射的数据。分析了两个林分中林冠结构、ULE 和空间异质性的季节性变化。结果表明，不同林分类型和季节之间的林冠结构和 ULE 指数存在高度显著（<0.01）差异。MF 的 CO 和 ULE 指数（Tdir、Tdif 和 Ttot）明显低于 PF，而 MF 的 LAI 明显高于 PF。CO 在夏季比冬季低，LAI 和 ULE 指数在夏季比冬季显著高。此外，林冠结构和 ULE 指数在不同类型的林分之间存在显著差异。MF 的 LAI 异质性低于 PF，夏季的 Tdir 异质性高于冬季。同时，林冠结构和 ULE 指数主要受结构因素影响，在 10 m 尺度上具有空间相关性。研究结果表明，森林类型和季节是影响亚热带山地森林林冠结构、ULE 特征和异质性的重要因素。
