潮间带贝克喜盐草土壤种子库空间分布及其生物影响因素

【目的】为探讨贝克喜盐草(Halophila beccarii Ascherson)种群更新及濒危机制,研究其土壤种子库空间分布特征及其生物影响因素。【方法】对广西合浦榕根山、防城港交东、防城港山心3个贝克喜盐草典型分布点进行调查取样,统计(或称量)样品种子、直立茎、雌花、果实数量、地上部分生物量和地下部分生物量。【结果】从水平方向分布来看,相同方向上不同距离处贝克喜盐草土壤种子库密度差异不显著,海草场潮沟、外海、海岸方向一侧的土壤种子库密度在榕根山和交东分别为271粒/m~2、180粒/m~2、52粒/m~2和52粒/m~2、23粒/m~2、16粒/m~2,差异显著,可见该海草种子水平空间分布格局受到落潮水流与落潮后流向潮沟的微水流的影响,受距离影响较弱;垂直方向上,上层(0~4cm)、中层(4~8cm)、下层(8~12cm)土壤底质中贝克喜盐草种子数量分别占总量的73.0%、20.8%和6.2%,上层土壤中种子数量显著高于中层和下层(P0.05),表明绝大部分的种子分布于土壤表层(0~8cm);贝克喜盐草海草场土壤种子库密度与其种群雌花密度、直立茎密度存在极显著线性正相关关系,其相关系数r分别为0.722 9(P0.01)、0.845 1(P0.01),与果实密度、地上部分生物量及总生物量呈多项式曲线关系。【结论】贝克喜盐草土壤种子库的水平空间分布受潮沟、入海河流等外界环境和地上植被的种群属性、种子自身特性等因素的影响,垂直方向上主要分布在表层底质中,且地上植被的种群属性是决定土壤种子库密度的关键因素。

Spatial Distribution of the Soil Seed Banks of Seagrass Halophila beccarii at Intertidal Zone and the Biological Influential Factors

[Objective] In order to explore the population regeneration and the cause of endangerment of Halophila beccarii, the spatial distribution characteristics of soil seed banks and its biological influential factors were studied.[Methods] Sediment including seagrass plants were sampled from three typical sites of seagrass H.beccarii in Guangxi at Ronggenshan of Hepu,Jiaodong and Shanxin of Fangchengang.The number of seagrass seeds,shoots,female flowers,and fruits in the samples were analyzed statistically and the seagrass biomass of above ground and below ground were weighed in the laboratory.[Results] We got the results in 3 aspects:Horizontally,there was no significant difference of the soil seed banks density among the distances at the same direction. The soil seed densities of the seagrass at the side to open sea,tidal creek,land at Ronggenshan and Jiaodong were significantly different at 271/m²,180/m²,52/m² and 52/m²,23/m²,16/m² respectively,revealing that the horizontal distribution patterns of H.Beccarii seeds were affected by both tidal flow of ebb tide and the thin flow of seawater down to tidal creeks and were weakly affected by distance;Vertically,73.0% of the seeds of H.Beccarii were found in the upper layer of sediment (0-4 cm),20.8% in the middle layer (4-8 cm) and 6.2% in the lower layer (8-12 cm),the number of the seagrass seeds in the upper layer was significantly higher than those in the middle and the lower layers (P<0.05),showing that most of the seeds distributed in the surface layer of the soil (0-8 cm); The soil seed densities of H.Beccarii were significantly linearly dependent on the densities of female flowers and shoots of the seagrass population.The correlation coefficients r was 0.722 9 (P<0.01) and 0.845 1 (P<0.01) respectively,and the fruit density,the above ground biomass and total biomass were in the polynomial curve.[Conclusion] Horizontal distribution of the soil seed banks of H.beccarii were mostly affected by some environmental factors such as tidal creeks and seagoing rivers,and the population attributes of above ground vegetation and seed properties.Population attributes of above-ground vegetation were the key influential factors that affected the densities of soil seed banks of H.Beccarii.