千岛湖岛屿马尾松林不同耐阴性植物幼苗动态研究

Seedling dynamics of shade tolerant and intolerant woody plants in the Masson pine forests on islands of the Thousand Island Lake

马尾松林是广泛分布于我国亚热带地区的代表性森林类型,多呈斑块状.马尾松林多处于干扰后森林群落演替的早期阶段,其后期可能演替为本地区的地带性植被——常绿阔叶林.因此,了解斑块生境中马尾松林的更新演替动态,对管理我国亚热带地区森林的物种多样性和生态系统功能具有重要意义.以千岛湖岛屿马尾松林内不耐阴和耐阴植物幼苗的短期动态为研究对象,试图了解片段化斑块生境中马尾松林的更新动态特点.结果发现：在0.5~3.5a的多个时间尺度上,耐阴植物幼苗的存活能力较不耐阴植物幼苗强,而耐阴植物和不耐阴植物幼苗的补员率和相对生长率并无差异.岛屿面积和岛屿形状指数对于幼苗存活和补员无显著影响.同时,耐阴灌木的幼苗组成中占绝对优势,而其他功能群幼苗比例较低,表明千岛湖岛屿马尾松次生林内耐阴植物更新较不耐阴植物好;岛屿大小和形状对更新群落的短期动态无明显作用;群落更新层的优势功能群为耐阴灌木.结果提示：千岛湖的片段化马尾松林林下层动态的方向性,有利于耐阴植物更新;但在较短时间尺度（≤3.5a）上,片段化斑块的性质对于群落幼苗更新的影响可能较小;耐阴灌木在片段化马尾松林林下层有优势地位.

Secondary Masson pine forests represent an important forest type in subtropical China,most of them is in fragments.Masson pine forests are the early stage of forest succession after disturbance,of which the late stage might be the typical regional subtropical evergreen broad-leaved forests.Understanding the regeneration dynamics of fragmented secondary Masson pine forests is critical to the management of regional forest biodiversity and ecosystem functioning.Therefore,we explored the short term seedling dynamics of shade tolerant（ST）and intolerant（SI）plant species in the secondary Masson pine forests on the islands of Thousand Island Lake（TIL）.We found that ST species showed higher seedling survival rate than SI species,while ST and SI species were not different in seedling recruitment rate and relative growth rate（RGR）at multiple time intervals ranging from 0.5to 3.5a.We also found that seedling survival and recruitment were not influenced by island size and island shape index.Meanwhile,shade tolerant shrub dominated over seedling composition,but other functional groups were low in relative abundance.These results imply that ST species regenerate better than SI species in the Masson pine forests on the islands of TIL.Island area and shape index may not largely influence the short term forest seedling regeneration dynamics,and the major functional group of community regeneration is shade tolerant shrub.This study suggests that the seedlingdynamics of the fragmented Masson pine forests is directional,favoring ST species regeneration.However,its short-term（≤3.5a）seedling dynamics may not be sensitive to fragmented status,and the dominance of shade tolerant shrub is in the undergrowth layer of these forests.