青海省东北部森林林下物种多样性的驱动因素

Driving factors of understory species diversity in forest on the northeastern Qinghai Province of northwestern China

【目的】青藏高原是对全球气候变化响应最敏感的区域之一,青海省东北部是整个青藏高原乔木林的重要分布区域,探讨青海省东北部森林林下物种多样性的驱动机制,可以为气候变化条件下的物种多样性保护和森林经营管理提供科学依据。【方法】以青海省东北部森林为研究对象,基于29个乔木样方、116个灌木样方和116个草本样方林下物种多样性的野外调查数据,利用广义最小二乘法(GLS)分析林下物种多样性和生物(林分结构)、非生物因素(包括气候、地形和土壤等)之间的关系。【结果】(1)青海省东北部森林群落树种组成单一,多以纯林为主,物种多样性主要由林下植被贡献。29个乔木样方共调查到维管植物108种,隶属44科89属,物种组成以蔷薇科、忍冬科和小檗科植物为主。林下层中,草本物种多样性显著高于灌木物种多样性(P<0.001)。(2)气候和林分结构是影响林下物种多样性最重要的驱动因素,相对影响分别占34.9%和26.2%。(3)灌木层和草本层物种多样性的关键驱动因素不同,灌木层物种多样性主要受林分结构影响(44.0%),而草本层物种多样性主要受到土壤(28.8%)和气候(28.2%)等非生物因素的影响。【结论】青海省东北部森林群落林下灌木层植被和草本层植被物种多样性的驱动机制存在差异,因此,在生物多样性保护和森林经营管理过程中应当充分考虑不同层次物种的反馈机制。

[Objective] The Qinghai-Tibet Plateau in the northwestern China is one of the most sensitive regions to global climate change.The northeastern part of Qinghai Province is an important distribution area of forests on the Qinghai-Tibet Plateau.Exploring the biotic and abiotic driving factors of the understory species diversity on the northeast of Qinghai Province can provide a scientific basis for species diversity protection and forest management under climate change.[Method] Based on the field survey data of understory species diversity of 29 tree quadrats,116 shrub quadrats and 116 herb quadrats in the northeast of the Qinghai-Tibet Plateau,the relationships between understory diversity and biotic(stand structure),abiotic factors(including climate,topography and soil) were analyzed by the generalized linear model(GLS).[Result] The main results showed that:(1) the species composition of forest community in northeastern Qinghai Province was single,mostly pure forest,and the species diversity was mainly contributed by understory vegetation.A total of 108 species of vascular plants belonging to 89 genera and 44 families were found in 29 quadrats.Rosaceae,Caprifoliaceae and Berberidaceae were the main species.The diversity of herbaceous species was significantly higher than that of shrub species(P < 0.001).(2) Climate and stand structure were the most important driving factors,accounting for 34.9% and 26.2%,respectively.(3) The key driving factors of species diversity of shrub layer and herb layer were different.The species diversity of shrub layer was mainly affected by stand structure(44.0%),and the species diversity of herb layer was mainly affected by abiotic factors such as edaphic(28.8%) and climate(28.2%).[Conclusion] There are differences in the driving mechanisms of species diversity between understory shrub layer vegetation and herbaceous layer vegetation in northeastern Qinghai Province.The feedback mechanisms of species at different levels should be fully considered in the process of biodiversity conservation and forest management of forest vegetation community in this region.