片段化生境中环境过滤和根系竞争对植物群落幼苗建立的影响

How to restore and reconstruct forest communities in fragmented habitats is an urgent need to understand the main factors that restrict the regeneration of plant communities. Seed germination, seedling survival, and growth are the key bottleneck stages of forest regeneration. However, current studies mainly focus on the effects of abiotic factors (environmental filtering) on seedling establishment stages caused by habitat fragmentation, ignoring the role of biotic factors such as competition of underground roots. This project chooses shade-tolerant and shade-intolerant species on Thousand Island Lake (TIL), Zhejiang province, China as the research objects. At the edge and interior of small and large island, seed germination and seedling growth in situ control experiments and laboratory control experiments with or without the competition of underground root were set up to test the effect of competition of underground root on seedling establishment. The degree of the effect of biotic (individual density of homologous and heterologous species, and root competition intensity of underground plants) and abiotic (e.g., soil and light condition) on seedling growth were compared and analyzed in different stages of seedling establishment for experimental species. We also test the effects of island area and edge effect on the relationship between factors and seedling establishment. Finally, we will reveal the key factors restricting the establishment of seedlings on islands. The results can provide a scientific basis for the restoration and conservation of plant communities in fragmented habitats.

了解片段化生境中限制植物群落更新的主要因子，有助于片段化森林的恢复和更新。幼苗建立阶段（出苗、幼苗的存活和生长）是群落更新的瓶颈阶段，但现有研究主要针对生境片段化所引起的非生物因子改变（环境过滤）对幼苗建立各阶段的影响，忽略了生物因子如植物根系的竞争作用。本项目以千岛湖岛屿上的耐阴种和非耐阴种为研究对象，在小岛和大岛上的边缘和内部，设置有无根系竞争作用的幼苗建立原位控制实验和室内控制实验，检验植物根系竞争对幼苗建立各阶段的影响；结合其他生物因子（如，同种和异种个体密度）和非生物因子（如，土壤、光照条件等），比较分析幼苗建立各阶段所受环境过滤和根系竞争作用的相对大小，并阐释岛屿面积效应和边缘效应对此作用的影响，揭示岛屿上限制幼苗建立的关键因子。预期为片段化生境中植物群落的恢复和保育提供科学依据。

全球约70%的森林植被正处于片段化生境中，生境片段化已成为影响生物多样性丧失的主要因子之一。了解片段化生境中植物群落的构建机制，有助于恢复片段化生境中的森林群落和提升其生物多样性及其生态系统功能。本项目利用千岛湖陆桥岛屿系统，结合非生物因子（如岛屿特征、土壤理化性质和生境异质性等）和生物因子（植食和种间竞争等），系统分析了影响岛屿上植物群落更新（种子萌发、幼苗存活和生长各阶段）和物种多样性维持等方面的关键生态因子。研究发现，在植物群落更新阶段，相较于岛屿面积等非生物因子和地下根系竞争的作用，植食作用（种子被取食和幼苗被植食）是影响岛屿上植物群落更新的关键因子。在岛屿植物群落物种多样性维持方面，岛屿面积显著影响岛屿上的物种多样性，而隔离度并无显著的影响，此外，岛屿面积与木本植物同种个体间作用强度的共同作用将显著增加岛屿上的物种多样性，揭示了与岛屿面积相关的环境过滤作用（即生物和非生物因子的选择过程）是影响岛屿上物种多样性维持的关键因子。上述研究结果表明，与植食过程相关的选择过程是影响岛屿上植物群落更新的关键限制因子，与岛屿面积相关的选择过程是影响岛屿上物种多样性维持的主要因子。该项目为片段化生境中植物群落的恢复和保育提供科学依据。