湿地土壤种子库与地上植被相似性关系研究评述

土壤种子库与地上植被的关系是土壤种子库研究的重要组成部分。当前,湿地生态系统面临严重威胁,研究湿地土壤种子库和地上植被关系既可以加强对土壤种子库和植物群落特征的认识,又可以为湿地保护与管理提供理论指导。检索了科学引文索引扩展版(SCIE)数据库中收录的1900—2012年间研究湿地土壤种子库与地上植被关系的文献,通过分析土壤种子库与地上植被的Srensen相似性系数,结果发现:不同湿地类型的土壤种子库和地上植被的相似性存在显著差异,河流湿地中两者的相似性最小;不同植被类型中土壤种子库与地上植被的相似性差异显著:草本群落的相似性大于乔木群落;不同气候带的湿地中两者的相似性也存在显著差异,其中亚热带地区相似性最小。总结了湿地种子库与地上植被相似性关系的时空变化特征。二者的相似性通常随着植物群落的演替而减小,在空间上也随着环境梯度而变化。分析了两者关系的影响因素,如种子传播、环境条件和繁殖策略等。对研究中存在的问题及发展方向提出建议。

A review of similarity between soil seed bank and aboveground vegetation in wetlands

The relationship between soil seed banks and aboveground vegetation is one of the most important components of soil seed bank research. It provides critical information on the nature of vegetation regeneration in ecosystems and ultimately guides the conservation and management of wetland biodiversity. In order to explore this relationship, using the Sørensen similarity index we reviewed the literature on the study of wetland soil seed banks and vegetation from 1900 to 2012, based on the Science Citation Index Expanded (SCIE). The results indicate that the similarity between soil seed banks and the vegetation of different wetland types varies significantly. Riverine wetlands had the lowest similarity between aboveground vegetation and seed banks compared with marshy wetland, lacustrine wetland and coastal wetland. Similarity varied significantly among different vegetation types, and herbaceous plant communities had a higher similarity than forested communities. A significant difference in the similarity index was also found among climatic zones, with the lowest in subtropical zones. This paper also reviewed the temporal and spatial characteristics of the relationship between wetland soil seed banks and vegetation. Similarity varied among seasons and years. Generally, the similarity index decreases with plant community succession; however, it varies in proportion to environmental factors, especially water disturbance. Most of the studies were conducted on a local scale using the space-for-time method. Long-term observational and landscape scale studies have become a new trend. Factors influencing their relationships were discussed in terms of seed dispersal, environmental conditions and reproductive strategy. Seed dispersal by wind, water and animals changes the species composition of the seed bank, making it different from the aboveground vegetation. Seeds that accumulate in persistent seed bank remain viable for a long period, which might otherwise perish in aboveground vegetation-one of the reasons for low similarity at the late successional stage. Environmental conditions, such as light, temperature and water conditions, are another mechanism driving plant community composition, affecting seed germination and seedling survival. The similarity is high in conditions suitable for seed germination and establishment, and low in unsuitable conditions. Differentiation in reproductive strategy between sexual reproduction and vegetative reproduction also resulted in a difference in species abundance in seed banks and in the similarity between seed banks and aboveground vegetation. The relationship between seed banks and vegetation can provide an insight into how the composition of plant communities changes in respect to disturbances, succession and restoration. A high similarity between seed banks and aboveground vegetation is more likely with the regeneration of vegetation on wetlands. In terms of wetland conservation and management, it is necessary to carry out assessments of targeted species and environmental evaluations of seed banks. For a comprehensive understanding of plant community structure and dynamics, it is proposed that future research should focus on the relationship between the soil seed bank and aboveground vegetation in wetlands. Long-term observation of wetland ecosystems and improved methods are suggested. At the same time, research suggests that there should be far more focus on how seed banks and aboveground vegetation influence each other and whether there is a threshold of similarity index indicating changes in plant community characteristics based on statistics. More studies should focus on the conservation and management of wetlands due to global climate change and human activity.