Abstract:

Ecosystem plant diversity and vegetation cover are seriously threatened by human activities, and a full understanding of the degradation process is key to achieving restoration of degraded ecosystems. Enclosure is a simple and effective strategy to restore damaged grassland ecosystems. However, the effects of different enclosure periods on plant diversity and landscape patches in degraded riparian grasslands are unclear. In the Liao River, the first riverine fenestration area established in China, as the study area, 21 monitoring sample sites were set up along the riverbank, and the density, cover, and species of riparian grassland were recorded for 13 consecutive years to explore the changes in plant community structure, species diversity, and vegetation landscape characteristics and their interrelationships under the degradation of riparian grassland to provide a theoretical basis for the management of grassland degradation in the riparian zone and the years of degradation of the degraded grassland for restoration. The results showed that (1) species richness and diversity increased significantly (p<0.05) with increasing enclosure years, and species richness, Shannon-Wiener index, Pielou homogeneity index, and Simpson dominance index peaked after 12 years of enclosure at 36, 2.87, 0.81, and 1.02, respectively. (2) The dissimilarity in community species composition increased with the number of years since enclosure. The eighth-year enclosure exhibited greater dissimilarity in species composition than the other enclosure years (p<0.05). The dominant plant species in the closed Liao River area were Compositae, Gramineae, and Leguminosae. (3) After the establishment of the reserve, vegetation patches dominated by natural landscapes were evenly distributed, vegetation coverage increased by 10.71%, and the degree of landscape fragmentation increased by 42.18%. In addition, riparian plant species diversity was positively correlated with vegetation coverage (p<0.001), whereas plant species diversity was negatively correlated with landscape fragmentation (p<0.001). In conclusion, 12 years of enclosure model improved the species diversity, species composition, and vegetation coverage of degraded riparian vegetation.

Key words: riparian vegetation, ecological enclosure, species diversity, vegetation cover, landscape fragmentation

摘要：

充分认识生态系统植物多样性和植被覆盖度退化过程是开展和实现退化生态系统修复的关键。封育是恢复受损草地生态系统的一种简单有效的策略，但不同封育年限对退化河岸草地植物多样性和景观斑块的影响尚不清楚。以中国建立的第一个河流封育区——辽河为研究对象，沿河岸设置21个监测样地，连续13年记录河岸草地植物密度、盖度和种类，探讨了河岸草地退化下植物群落结构、物种多样性和植被景观特性的变化及其相互关系，为河岸带草地退化管理和退化草地恢复年限提供理论依据。结果表明，1）随着封育年限增加，物种丰富度和多样性显著提高（p<0.05），物种丰富度、Shannon-Wiener指数、Pielou均匀度指数和Simpson优势度指数均在封育12年后达到峰值，分别为36、2.87、0.81和1.02。2）随着封育年限的增加，群落物种组成差异也在增大，封育第8年与其他围封年限的物种组成相比差异较大（p<0.05），辽河封育区的优势植物种类主要为菊科、禾本科和豆科植物。3）封育12年后，以自然景观为主的植被斑块分布均匀，植被覆盖度提高10.71%，景观破碎化程度降低了42.18%。此外，河岸植物物种多样性和植被覆盖度正相关（p<0.001），而植物物种多样性和景观破碎度负相关（p<0.001）。综上，12年围栏封育阈值提高了退化辽河干流河岸草地物种多样性、物种组成和植被覆盖度。

关键词: 河岸植被, 生态封育, 物种多样性, 植被覆盖, 景观破碎化