粤东沿海红树林物种组成与群落特征

南海地区是全球红树林分布的中心区域之一。粤东沿海位于南海地区的北界,红树林物种组成和群落结构具有边缘性。利用卫星影像解译辅助技术,对筛选的23处红树林群落进行样地调查,记录了真红树植物12种,半红树植物6种,伴生植物7种。各群落平均高度为1.50—8.60 m,林相以灌丛、小乔木林为主。红树林群落Shannon-Wiener多样性指数为0.533—1.239,均匀度指数为0.662—0.957,天然林和人工林之间数值差异不显著。等级聚类分析将粤东沿海的红树林划分为演替早期人工林、演替早期天然林、演替中期天然林和演替后期天然林4个类别,各群落立地条件差异较大,沉积物总有机碳、盐度、总氮含量与群落分布状况的相关性较高。与1985年的报道相比,尽管该地区记录的红树林植物种类从20种增加至24种,但个别伴生植物消失以及半红树植物种群萎缩说明该地区红树林面临较大的环境压力。在物种多样性和均匀度均方面,粤东沿海红树林群落低于成熟红树林。过去数十年的围垦导致天然红树植物种群萎缩、生境破碎化是主要因素。基于该地区红树林群落的现状,未来人工林和残次天然林的优化改造是红树林恢复重建的重点,红树林恢复和保育的重点区域包括深圳湾的福田、范和港的蟹洲和韩江口的六合围。

Current state of mangrove floristic composition and characteristics of communities on the eastern coast of Guangdong Province

The South China Sea is one of the mangrove hotspots in the world. The eastern coast of Guangdong Province is located at the northernmost boundary of the South China Sea and is characterized by the marginal mangrove floristic composition and communities. Using satellite imagery interpretation, 23 sites were chosen and surveyed. A total of 12 species of true mangrove, six species of semi-mangrove, and seven species of associated plants were recorded in the surveyed sites. The main forms of mangrove communities were shrubs and dwarf trees with the average height of 1.50 to 8.60 m. The Shannon-Wiener index ranged from 0.533 to 1.239, while the evenness index varied from 0.662 to 0.957. There was no significant correlation in these indices between natural forests and plantations. The mangrove communities were classified into four types: pioneer plantation, pioneer natural forest, medium natural forest, and climax natural forest. The environmental factors between forest stands differed significantly, and total organic carbon, salinity, and total nitrogen in sediments were highly correlated with community distribution. Although plant species abundance increased from 20 to 24 species compared to the data obtained in 1985, reduction in some associated plants and retreated semi-mangrove populations indicated that the mangrove in eastern Guangdong were facing tremendous environmental pressure. Species diversity and evenness in the mangrove in eastern Guangdong were lower than those of mature mangroves. Reclamation in the past several decades contributed to natural mangrove decrease and habitat fragmentation. Given the current state of mangrove vegetation, improvement in plantations and residual secondary natural forests is the focus of mangrove restoration in key areas, including Futian in Shenzhen Bay, Xiezhou in Fanhe Harbour, and Liuhewei in Hanjiang Estuary.