亚热带生态公益林冠层结构与林下辐射动态

冠层结构动态是林冠生长动态的一个表现，冠层结构对森林群落生产力、生态系统功能、群落更新与演替等具有重要作用。准确量化森林群落冠层结构和林下辐射特征可以为研究森林生态系统功能提供基础。以亚热带山地的红花荷林、密花树次生林、樟树人工林、杉木林、杉木-红锥混交林和毛竹林为对象，利用半球面影像技术探讨不同林型冠层结构与林下辐射动态，揭示冠层结构与林下辐射之间的相关性。结果表明，不同的森林群落类型有比较固定的冠层结构和林下辐射特征，且不同林型的冠层结构与林下辐射存在极显著差异（P<0.01）。樟树林的林冠开度最小（16.47%），其次是杉木林（17.12%）、杉木-红锥混交林（17.45%）、红花荷林（20.21%）以及密花树次生林（20.93%），毛竹林的林冠开度最大（21.32%）。而叶面积指数则呈相反的变化趋势，樟树林的叶面积指数最大（2.04），毛竹林的叶面积指数最小（1.78）。另外，樟树人工林的林下直射光（4.34 mol·m^-2·d^-1）、林下散射光（3.52 mol·m^-2·d^-1）和林下总光照（7.86 mol·m^-2·d^-1）均小于其他林型；而杉木林由于其冠幅较窄，林下直射光最强（5.22 mol·m^-2·d^-1）。不同林型林下直射光、林下散射光和林下总光照的月际动态变化极显著（P<0.0001），生长季的林下辐射强度最大。不同林型冠层结构与林下辐射相关性存在差异，越简单的群落结构，林冠开度与林下光照的相关性越强，叶面积指数与林下光照的相关性越强。研究冠层结构与林下辐射异质性为营造最适的冠层、充分发挥生态系统效能，以及森林生态系统可持续发展提供理论依据。

Canopy Structure and Understory Radiation Dynamics of Subtropical Ecological Public Welfare Forest

The dynamics of canopy structure is a manifestation of canopy growth dynamics.The heterogeneity of canopy structure plays important roles in forest community productivity,ecosystem function,community renewal and succession.Accurately quantifying the canopy structure and understory radiation characteristics of forest communities can provide a unique perspective for studying the forest ecosystem functions.In this study,several different forest types were used as the research objects,including Rhodoleia championii,Rapanea neriifolia,Cinnamomum camphora,Cunninghamia lanceolata,C.lanceolata-Castanopsis hystrix and moso bamboo in subtropical mountains to explore the canopy structure and understory radiation dynamics.The relationship between canopy structure and understory radiation was revealed by using hemispherical photography.The results showed that different forest community types had relatively fixed canopy structure and understory radiation characteristics with significant differences among different forest types(P<0.01).The canopy openness of C.camphora was the smallest(16.47%),followed by C.lanceolata(17.12%),C.lanceolata-C.hystrix(17.45%)R.championii(20.21%),R.neriifolia(20.93%),and moso bamboo(21.32%).The leaf area index(LAI) showed an opposite trend,the LAI of C.camphora was the largest(2.04),and the smallest for moso bamboo(1.78).In addition,the transmitted direct radiation(4.34),transmitted diffuse radiation(3.5) and transmitted totals radiation(7.86) under C.camphora were all smaller than other forest types,while the transmitted direct radiation of C.lanceolata(5.22) was the strongest because of its narrow canopy.The monthly dynamic changes of transmitted direct radiation,transmitted diffuse radiation and transmitted totals radiation were very significant(P<0.000 1),and the understory radiation intensity was the highest in the growing season.There were differences in the correlation between canopy structure and understory radiation among different forest types.The simpler the community structure,the stronger the correlation between canopy openness and understory radiation,and the stronger the correlation between leaf area index and understory radiation.The study of canopy structure and understory radiation heterogeneity would provide a theoretical basis for creating the most suitable canopy,and give full play to ecosystem efficiency and sustainable development of forest ecosystem.