极小种群野生植物黄梅秤锤树群落结构与动态

Community structure and dynamics of a remnant forest dominated by a plant species with extremely small population(Sinojackia huangmeiensis) in central China

本文以极小种群野生植物黄梅秤锤树(Sinojackia huangmeiensis)当前唯一的野生种群为依托建立了1 ha的固定样地,研究了黄梅秤锤树野生植物群落的物种组成、优势种的径级结构、黄梅秤锤树的空间分布格局、种内与种间空间关联性和种群更新特征。样地内共记录到胸径≥1.0 cm的木本植物31种,隶属于21科28属。群落更新良好,样地中所有1,225株个体中小径木占比为67.18%。群落优势种为麻栎(Quercus acutissima)、枸骨(Ilex cornuta)、朴树(Celtis sinensis)和黄梅秤锤树。麻栎的径级结构呈单峰型,为衰退型种群;枸骨、朴树和黄梅秤锤树的径级结构呈倒"J"型或偏倒"J"型,表明更新良好。黄梅秤锤树的空间分布格局在小尺度上呈聚集分布,在大尺度上呈随机或均匀分布,并且与其他3个优势种(麻栎、枸骨、朴树)在空间上主要呈负关联性。黄梅秤锤树的成树和幼苗、幼树和幼苗都是在小尺度上呈负关联性,在大尺度上关联性不显著,而成树和幼树在整体上关联性不显著。黄梅秤锤树的萌蘖现象非常明显,萌蘖数与母株胸径具有极显著的正相关性(R^2=0.330,P<0.001),萌蘖率与相对幼苗密度具有极显著的负相关性(R^2=0.438,P<0.001)。总体来说,高比例的小径木和普遍的种间负关联均表明该群落处于演替的早中期,物种组成和群落结构还未达到稳定阶段。作为长江中下游冲积平原区具有代表性的残存风水林,该野生植物群落在生物多样性维持和珍稀植物保护方面具有重要的作用,应加强保护和管理。

In China, Sinojackia huangmeiensis is among the 120 plant species with extremely small populations（PSESP）, with only one extant wild population located at the lakeside of the Longgan Lake, central China. Here, we followed the field protocol of the 50-ha permanent forest plot on the Barro Colorado Island in Panama to census all free-standing woody species ≥ 1 cm diameter at breast height（DBH） in a 1-ha plot established in a lowland fengshui forest dominated by S. huangmeiensis. We recorded a total of 1,225 living individuals, belonging to 31 species, 28 genera and 21 families. Individuals with DBH 7.5 cm accounted for ca. 67% of all individuals, indicating good natural regeneration in the community. The most dominant species were Quercus acutissima, Ilex cornuta, Celtis sinensis, and S. huangmeiensis. Quercus acutissima showed a single peak pattern of diameter class distribution, while I. cornuta, C. sinensis, and S. huangmeiensis showed a reverse ＂J＂ shape or a partial reverse ＂J＂ shape. S. huangmeiensis showed aggregated distribution at small spatial scales and random or uniform distributions at large scales. Individuals of S. huangmeien-sis were negatively associated with the other three dominant species. Seedlings of S. huangmeiensis were negatively associated with both conspecific saplings and adults at small scales, but showed no correlation at other scales. There was a significantly positive correlation between sprout number and DBH of S. huangmeiensis（R2 = 0.330, P〈 0.001）, whereas ratio of sprout and relative seedling density showed a negative correlation（R2 = 0.438, P 〈0.001）. In general, high percentage of small-sized individuals and interspecific negative associations suggested that this plant community is still at an early-to-middle stage of succession. The remnant fengshui forests in the lowland plains of the middle and lower reaches of the Yangtze River are important for their roles in the conservation of biodiversity and endangered plants and should therefore be protected and well-managed.