濒危海草贝克喜盐草的种群动态及土壤种子库——以广西珍珠湾为例

Abstract

PDF HTML阅读 XML下载 导出引用 引用提醒 濒危海草贝克喜盐草的种群动态及土壤种子库——以广西珍珠湾为例 DOI: 10.5846/stxb201306091489 作者: 作者单位: 中国科学院生态环境研究中心,广西科学院 广西红树林研究中心,中国科学院生态环境研究中心 城市与区域生态国家重点实验室,中国科学院生态环境研究中心,中国科学院烟台海岸带研究所,广西科学院 广西红树林研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 广西"红树林和海草系统保育与生态监测"特聘专家岗位基金资助项目;广西自然科学基金资助项目(0832030);广西科学院基本科研业务费资助项目(13YJ22HS12);广西青年科学基金资助项目(2012GXNSFBA053141);国家青年科学基金项目(31000210) Population dynamics and seed banks of the threatened seagrass Halophila beccarii in Pearl Bay, Guangxi Author: Affiliation: State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences,,,State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:于2012年4月-2013年4月调查了广西珍珠湾地区贝克喜盐草(Halophila beccarii Ascherson)种群的基本属性及土壤种子库储量。结果表明,不同月份间该种群的面积、覆盖率、直立茎密度、生物量、繁殖器官密度等属性差异明显,均呈现先增大后减小再增大的趋势;各个属性出现峰值的日期有所不同,面积、覆盖度、地下生物量和总生物量的最高峰值出现在10月底,而直立茎密度和地上生物量峰值最高峰值出现在8月初。贝克喜盐草珍珠湾种群有明显雌蕊先熟现象,雌花发育高峰期(8月初,5404 朵/m2)早于雄花发育高峰期(8月底,2189 朵/m2)。而果实高峰期(4125 个/m2)为10月份。地上与地下生物量之比值(1.95-0.53)随种群的发育而逐渐减小,基于此比值可判断贝克喜盐草种群所处的发育阶段。在生长高峰期,贝克喜盐草种群有较大的分布面积(21.4 hm2)、较高的覆盖度(55%)、直立茎密度(21602 茎/m2)及生物量(70.583 g/m2干重)。贝克喜盐草果实含种子为1-4粒(平均为2.22粒);1月、3月和4月土壤种子库密度分别为5749、5652、2728 粒/m2,3-4月期间土壤种子库种子损失率高达104 粒 m-2 d-1。尽管贝克喜盐草有较高的种子产量(10月份,9158 粒/m2)和较快的生长速度,但由于土壤种子库中种子损失严重且种子萌发率较低以及人为干扰对其生境的强烈干扰等因素,因此可能会对次年的种群更新产生较大的负面影响。 Abstract:Halophila beccarii Ascherson is one of two species in the oldest lineage of seagrasses, and belongs to the family Hydrocharitaceae. It is a small submerged creeper, found in the upper intertidal zone, and grows on mud or muddy sand substrates in estuarine and coastal areas. This species has been recorded to be at the coastlines of East Asia, Southeast Asia, Central Asia, Kenya and Tanzania. Global population trends indicate this species is declining, although it is fast growing and may recover quickly from disturbance. However, it also has a narrow, restricted depth range that coincides with the intertidal zone, an area subject to much anthropogenic disturbance. This species was listed as ‘Vulnerable’ by the International Union for Conservation of Nature under criterion B2. H. beccarii occupies a very limited area in China and it is threatened by many forms of disturbance. Very little ecological information has been reported from China or subtropical regions globally for this species, and existing ecological studies are restricted to tropical regions in Southeast Asia or South Asia. The lack of basic ecological information on H. beccarii in China affects our understanding of the mechanisms underlying its decline, and thus hinders efforts to conserve and manage this threatened seagrass species. To examine temporal variation in the area, percent cover, above-ground/below-ground biomass, shoot density, reproductive organ density and the sediment seed banks of H. beccarii in Pearl Bay, Guangxi, samples were taken and surveys were carried out from April 2012 to April 2013 at roughly one-month intervals. Our results indicate that the area, percent cover, shoot density, biomass and reproductive organs density of H. beccarii in Pearl Bay vary greatly at different stages of population development over an annual cycle. Generally, all population parameters initially increased from April 2012, until they reached a peak value and then decreased. It seems the growth dynamics of the population followed "n" patterns with the peak values for shoot density (21602/m2), female flower density (5404/m2) and above-ground biomass (42.712 g/m2 (DW)) occurring in early August; male flower density (2189/m2) in late August; and area (21.4 hm2), percent cover (55%), below-ground biomass (39.701 g/m2 (DW)) and total biomass (70.583 g/m2 (DW)) in late October. We conclude that the flowers of H. beccarii in Pearl Bay are strongly protogynous. The ratio for above-ground to below-ground biomass decreases continuously from 1.95 to 0.53 during population development. Mean fruit density (as calculated from October 2012) was 4125/m2. Analysis of 186 H. beccarii fruits from Pearl Bay (1.7% of fruits had one seed, 79.7% had two seeds, 13.6% had three seeds and 5.1% had four seeds), revealed that seed counts varied from 1-4 with a mean of 2.22 mature seeds per fruit. Seed reserves in the soil varied with sampling location within the meadow, with an average of 5749/m2 in January, 5652/m2 in March and 2728/m2 in April. Based on our results for the area of seagrass and soil seed bank information, we estimate that the soil seed reserve of H. beccarii in Pearl Bay in January is about 1.23 × 109. We conclude that the H. beccarii population in Pearl Bay, Guangxi has the highest area, coverage, shoot density and biomass of all the sites where this species has been recorded in China. We suggest that the continuous decrease of the ratio of above-ground to below-ground biomass with population development means that the value of this ratio can be used as indicator for distinguishing between different developmental stages of H. beccarii populations. Despite being characterized by high seed production and fast growth, this species is threatened by high levels of human induced habitat disturbance, high rates of seed loss in sediments and low seed germination rates, which are all negatively affecting the regeneration of H. beccarii populations. 参考文献 相似文献 引证文献