林分结构对湖南栎类天然次生林林下植被生物量的影响

对湖南栎类天然次生林不同林分类型的林下植被生物量特征及其影响因素进行研究。结果表明: 将50块样地划分为甜槠-鹿角杜鹃混交林、亮叶水青冈-箭竹混交林、石栎-虎刺+山茶混交林、甜储+枹栎-鹿角杜鹃混交林、青冈栎-油茶+杜鹃混交林5种林分类型。5种林分的林下植被生物量均较低,不超过2.3 t·hm^-2。5种林分类型的林下灌木生物量没有显著差异,甜槠-鹿角杜鹃混交林草本层生物量显著低于其他4种林分类型。影响不同林分林下植被生物量的因素不同。在甜槠-鹿角杜鹃混交林,草本层生物量与郁闭度、角尺度呈显著负相关,林下植被总体生物量与开敞度呈显著正相关;在亮叶水青冈-箭竹混交林,灌木层生物量与林分的角尺度、郁闭度呈显著负相关,草本层生物量与林下植被总体生物量与混交度呈显著正相关;在石栎-虎刺+山茶混交林,草本层生物量与林分的聚集指数呈显著正相关;在甜储+枹栎-鹿角杜鹃混交林,灌木层生物量与林分的混交度呈显著负相关,草本层生物量与林分的株数密度呈显著正相关;而在青冈栎-油茶+杜鹃混交林,林分结构与林下生物量没有显著相关关系。对林下植被生物量进行调整,应该以调整林分水平分布格局为主,综合考虑林分遮盖程度与树种结构。

Effects of stand structure on understory biomass of the Quercus spp secondary forests in Hunan Province,China

We examined biomass characteristics and the potential driving factors of different forest types of Quercus spp. secondary forest in Hunan. A total of fifty plots were divided into five forest types: Castanopsis eyri - Rhododendron latoucheae mixed forest (CR), Fagus lucida - Fargesia spathacea mixed forest (FF), Lithocarpus glaber - Damnacanthus indicus + Camellia japonica mixed forest (LDC), C. eyri + Quercus serrata - R. latoucheae mixed forest (CQR), Cyclobalanopsis glauca - Camellia oleifera + R. latoucheae mixed forest (CCR). The biomass of understory vegetation was low in the five forest types, being smaller than 2.3 t·hm^-2. There was no significant difference in the biomass of understory shrubs among the five forest types. The biomass of herbage layer in CR was significantly lower than that of the other four forest types. The factors affecting the biomass of understory vegetation varied in different forests types. In CR, biomass of herbaceous layer was negatively correlated with canopy and uniform angle index, whereas total understory biomass was positively correlated with opening degree index. In FF, biomass of shrub layer was negatively correlated with stand canopy density and uniform angle index, while herbaceous biomass and total understory biomass were positively correlated with stand closure. In LDC, herbaceous biomass was positively correlated with the stand aggregation index. In CQR, shrub biomass was negatively correlated with stand mingling index, while herbaceous biomass was positively related with stand density. In CCR, there was no significant correlation between stand structure and understory biomass. To adjust the understory biomass, we should first adjust the horizontal distribution pattern of stand and then adjust the degree of forest cover and tree species structure.