湖南八面山银杉群落特征及其残遗性和保守性分析

Analyses on community characteristics and its relict and conservation of Cathaya argyrophylla at Bamianshan in Hu'nan Province

为了解中国特有孑遗植物银杉(CathayaargyrophyllaChunetKuang)的生存现状,对位于湖南八面山脚盆辽的银杉+南方铁杉也Tsugachinensisvar.tchekiangensis(Flous)ChengetL.K.Fu页+甜槠也Castanopsiseyrei(Champ.)Tutch.页-猴头杜鹃(RhododendronsimiarumHance)群落进行调查,分析其群落特征及种群年龄结构,比较分布在不同区域的6个银杉群落中种子植物属的分布区类型及其相似性系数;在此基础上,讨论了银杉群落的残遗性特征。结果显示:脚盆辽银杉群落共有维管植物66种,包括蕨类植物4种和种子植物62种(裸子植物4种、被子植物58种);该群落乔木层的主要优势种为甜槠、猴头杜鹃、银杉和南方铁杉,重要值分别为13.12%、9.28%、8.86%和7.49%;该群落的Simpson和Shannon-Wiener多样性指数分别为0.94和3.20,Pielou均匀度指数Jsw和Jsi分别为0.81和0.92,说明该群落物种多样性偏低但物种分布均匀,与中亚热带山地的暖性针阔叶混交林特征一致。从生活型谱看,该群落中各频度百分比由高至低依次为A级、B级、C级、D级、E级,与Raunkiaer标准频度图谱基本一致,表明该群落整体上处于较为稳定的亚顶极状态。从银杉种群年龄结构看,种群中幼龄个体占一定比例,但80~180a的中龄个体比例偏低;从该群落优势种的径级结构看,甜槠、猴头杜鹃和鹿角杜鹃(RhododendronlatoucheaeFranch.)种群为增长型种群,而银杉、南方铁杉和福建柏也Fokieniahodginsii(Dunn)HenryetThomas页种群为衰退型种群。从脚盆辽银杉群落种子植物属的分布区类型看,温带分布型属占51.06%,略高于热带分布型属(占48.94%),说明该区域属于热带亚热带过渡区;除纬度外,海拔也能够在一定程度上影响其分布区类型组成。在处于粤北、粤桂山地和贵州高原3个植物区系亚地区的6个银杉群落中,种子植物属分布区类型的相似性系数为0.35~0.67,群落建群种所在属如铁杉属也Tsuga(Endlicher)Carri侉re页、润楠属(MachilusNees)、水青冈属(FagusLinn.)和福建柏属(FokieniaHenryetThomas)等在各群落间有相似性和共通性,且多为古老成分和孑遗成分,表明现存的银杉群落具有相近的变迁历史,分布地域具有明显的亚热带山地避难所特征,体现出其演替过程的残遗性和保守性。研究结果表明:在银杉群落中适度疏通林窗,降低林下郁闭度,有利于银杉幼树的生长,使银杉种群得到可持续更新和演替。

In order to understand current survival status of Chinese endemic relic plant Cathaya argyrophylla Chun et Kuang, C. argyrophylla+Tsuga chinensis var. tchekiangensis (Flous) Cheng et L.K. Fu + Castanopsis eyrei ( Champ.) Tutch. - Rhododendron simiarum Hance community located at Jiaopenliao of Bamianshan in Hunan Province was investigated, its community characteristics and population age structure were analyzed, and generic arealtype and its simlarity coefficient of spermatophytes in six communities distributing in different regions were compared.