西门岛人工秋茄林恢复对大型底栖生物的影响

Influences of artificial Kandelia obovata mangrove forest rehabilitation on the macrobenthos in Ximen Island

选择乐清湾西门岛海域相同高程断面不同造林时间的人工红树林(秋茄林)、光滩和互花米草丛,采用空间代替时间的方法,分析我国分布最北界人工红树林造林过程对大型底栖生物的影响。大型底栖动物生活型分布基本表现为幼林(1、4、8a秋茄林)以底上附着型为主,而在光滩、50a秋茄林和互花米草中底下生活类群相对增加。并且穴居型动物只出现在发育成熟的生态系统内。各项指标显示50a老林群落生态稳定性较好,光滩和互花米草丛次之,但优于发育中的秋茄幼林。与以往研究结果不同,50a老林的大型底栖动物生物种类的丰度及群落的物种多样性最高,并不与红树林的发育状况呈负相关,也不比邻近光滩低。结合50a林下滩涂底泥情况,西门岛50a红树林林下滩涂的底质发育要落后于国内天然红树林土壤。这可能与当地红树林造林规模小以及强潮差海域有关。此外,红树林恢复过程中,大型底栖动物生物多样性与生态稳定性之间的线性关系,其适用的系统面积和演替时间的尺度范围有必要做更加深入的探讨。

Macrobenthos is an important part in mangrove ecosystem, and plays a connection link in energy flow and matter cycling. Its community structure can reflect the level of mangrove forest rehabilitation by bottom sediment condition, water quality, vegetation and environmental pressure and so on. To reveal the effects of mangrove rehabilitation on macrobenthic communities, a seasonal investigation （from October 2010 to May 2011 ） on the macrobenthic assemblages was performed in six habitats, including four artificial Kandelia obovata forests with different ages, Spartina alterniflora （Sa） marsh, and naked beach （NB） in Ximen Island in southeastern China. The four mangrove forests were 1-year old replanted mangrove forest （M1）, 4-years old replanted mangrove forest （M4）, 8-years old replanted mangrove forest （M8） and 50-years old replanted mangrove forest （M50）. To avoid the effects of tidal elevation, all the six habitats had the same elevation. A total of 24 macrobenthic species were recorded, including Polychaeta, Mollusca, Crustacean and others. The members of Mollusca and Crustacean were dominant and dominant species were found to be different among various habitats. Phascolosoma esculenta and Littoraria melanostoma were the dominant species in M50, while Assiminea latericea, Batillariazonalis, and Cerithideopsilla cingulata were the dominant species in the others. Young mangrove forests were dominated by surface adhering group, while the older mangrove forest （ M50 ）, NB and Sa were dominated by infauna. Moreover, it revealed that caving animals appeared only in mature ecosystems which are more stable, such as NB, Sa and M50. There were differences in macrobenthic assemblages among the six habitats and M50 showed the highest stability in terms of ecological function as indicated by the highest abundance and species diversity of macrobenthos. This result was different from those of previous researches, which suggested a negative relationship between the abundance and diversity of macrobenthos and the mangrove development. This difference was probably due to the differences in sediment and soil development. Compared with typical natural mangrove forest, M50 had less litter and semi-decomposed litter in the sediments. Furthermore, the sediment in M50 lacked the typical smelly and black-color appearance which is typical of natural mangrove forest. Therefore, our results suggested that the sediment of M0 in Ximen Island developed slower than those of natural ones, which may be due to the limited planting scale and the larger tidal range in Ximen Island. Generally, further researches focusing on the linear relationship between the macrobenthos biodiversity and the ecosystem stability, especially its applicable temporal and special scale are required.