湖北七姊妹山亚热带常绿落叶阔叶混交林的物种组成和群落结构

Species composition and community structure of a 6-ha subtropical evergreen and deciduous broad-leaved mixed forest dynamics plot in the Qizimei Mountains, Hubei Province

亚热带常绿落叶阔叶混交林是亚热带山地中重要的森林植被类型之一,是维持区域生态安全和保护生物多样性的重要屏障。为深入研究亚热带常绿落叶阔叶混交林中的生物多样性维持机理和动态过程,我们在湖北恩施七姊妹山国家级自然保护区6 ha亚热带常绿落叶阔叶混交林动态监测样地调查了所有胸径(DBH)≥1 cm的木本植物,分析了其群落组成、径级结构和优势种的空间结构特征。共记录到木本植物50,316株,其中独立个体有36,596株(去除分枝和萌生),隶属于57科124属245种,包括7种国家级保护植物和76种稀有种(每公顷个体数不超过1株)。样地内落叶物种分别占总物种数的61.2%(150种)和总个体数的52.6%(26,503株)。整个样地内植物个体胸径呈明显的倒"J"型分布,平均胸径为4.38 cm。样地小径级木本植物较多,胸径≥30 cm的木本植物仅175株。样地中重要值排名前4位的物种分别是川陕鹅耳枥(Carpinus fargesiana)、多脉青冈(Cyclobalanopsis multinervis)、交让木(Daphniphyllum macropodum)和缺萼枫香(Liquidambar acalycina)。这些优势种虽然在整个样地均有分布,但大径级个体(DBH≥10 cm)的空间分布差异较为明显。依据群落组成和径级结构特征,湖北七姊妹山森林动态样地属于人为干扰后处于自然恢复中期的森林群落。针对该样地开展长期的森林动态监测,将有助于深入了解亚热带常绿落叶阔叶混交林恢复过程中的群落构建规律和物种多样性维持机制。

The subtropical evergreen and deciduous broad-leaved mixed forest （SEDBMF） is one of the most important forest vegetation types in subtropical mountainous regions. It can provide an important foundation to maintain regional ecological security and conserve biodiversity. To further explore maintenance mechanisms of species diversity in SEDBMF, a 6-ha forest dynamics plot was established in Hubei Qizimei Mountains National Nature Reserve, western Hubei Province in 2015. All living woody stems with diameter at breast height （DBH） ≥ 1 cm were tagged, identified, measured, and mapped according to the methods of CTFS （Center for Tropical Forest Science）. Community composition, diameter class structure, and characteristics of the spatial structure of dominant species were analyzed. Results showed that there were in total 50,316 stems and 36,596 independent individuals, belonging to 245 species 124 genera 57 families. Seven species that are national protected plants and 76 rare species （density ≤〈 1 stem/ha） occurred in this plot. Among those stems, 61.2% of total species and 52.6% of the total stems were deciduous tree species. The structure of DBH size-classes of all stems showed a reverse ＂J＂ shape. The average stem DBH was 4.38 cm and there were only 175 stems with DBH ≥ 30 cm in this plot. The top four dominant species in the plot were Carpinus fargesiana, Cyclobalanopsis multinervis, Daphniphyllum macropodum, and Liquidambar acalycina. They nearly distributed all around the plot but large size trees （DBH ≥ 10 cm） showed relatively different spatial distributions. Based on community composition and stem size structure, the Qizimei Mountains forest dynamics plot belongs to the middle stage of secondary forests after anthropogenic disturbance. Consequently, monitoring long-term forest dynamics in this plot will promote a deeper understanding of community assemblage rules and maintenance mechanisms of species diversity during the natural recovery process in SEDBMF.