Factors influencing landscape pattern of the seagrass Halophila decipiens in an oceanic setting
Factors influencing landscape pattern of the seagrass Halophila decipiens in an oceanic setting
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DOI：
10.1016/j.ecss.2007.06.014
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发表时间：
2008-01-01
影响因子：
2.8
通讯作者：
Bell, Susan S.
中科院分区：
文献类型：
--
作者：
Fonseca, Mark S.;Kenworth, W. Judson;Bell, Susan S.
生态群落景观格局形成的尺度可以为揭示影响其时空动态的过程提供线索。为了确定外部（飓风）和内部（克隆生长）因素的相对影响，我们在两个空间尺度和生长季节对开放海洋环境中的一年生海草（Halophila decipiens）进行了空间组织研究。海草覆盖的目视调查在2年多的时间里进行，在佛罗里达州西南海岸的一个近岸样带中，在10至30米的深度，在三个重复的1公里2研究区域内，每个研究区域间隔约25公里。拖曳式视频雪橇可以在研究区域内数千米均匀间隔的横断面上，大约每6米观察1米(2)面积的海草覆盖（粗比尺）。拖曳视频显示，17.5%的海底受到干扰，无论地点或采样时间如何。潜水员以0.625 m(2)分辨率（精细比例尺）在较大的1 km(2)研究区域内随机选择10 × 10 m样方，对海草覆盖进行全面调查。使用常规地质统计学和时间序列技术（Runs测试）对海草覆盖邻近尺度进行了粗尺度观测。使用常规地质统计学和最小二乘方法（累积逻辑）检查精细尺度观测。粗尺度观测结果显示尺度依赖性较小，表明结构在空间范围内的组织比我们的样本间距更细；累积逻辑技术揭示了潜在的精细尺度模式，否则无法识别。相比之下，对10 × 10 m样方的调查发现了具有多个小间隙的强烈尺度依赖性，表明在一般< 14 m范围内运行的过程产生的尺度依赖性模式。1999年6月至10月间，一场一级飓风经过研究区域，重新排列了大片的沙子，这些沙子覆盖了一些岩石坚硬的底部区域，同时覆盖了其他区域；到了下一个生长季节，新覆盖的地区长满了可能来自运输种子的嗜盐菌。空间分析表明，此次风暴导致了蠓出现频率的增加，但密度覆盖率的降低。风暴过后一整年，所有地区的海草密度都大幅下降。decipiens的短暂生活史和可移动种子库的明显存在意味着该群落的空间组织首先由植物繁殖体的大规模传播（数百米）决定，然后在生长季节内由海草的克隆组织在非常小的距离(m)内运作。两种方法（半方差检验和Runs检验）对海草景观格局的组织尺度得出了相似的结论。与陆地的例子一样，本研究表明选择合适的尺度对于检测影响海草生态系统种群生态的景观格局和过程的重要性。Elsevier Ltd.出版。
The scale of landscape pattern formation of an ecological community may provide clues as to the processes influencing its spatial and temporal dynamics. We conducted an examination of the spatial organization of an annual seagrass (Halophila decipiens) in an open ocean setting at two spatial scales and growing seasons to identify the relative influence of external (hurricanes) versus internal (clonal growth) factors. Visual surveys of seagrass cover were conducted over 2 years within three replicate I km 2 study areas each separated by similar to 25 km in an inshore-offshore transect along the southwest coast of Florida at depths between similar to 10 and 30 m. A towed video sled allowed observations of seagrass cover of 1 m(2) areas approximately every 6 m over thousands of meters of evenly spaced transects within the study areas (coarse scale). The towed video revealed that 17.5% of the seafloor was disturbed irrespective of location or sample time. Randomly selected 10 x 10 m quadrats within the larger, 1 km(2) study areas were completely surveyed for seagrass cover by divers at 0.625 m(2) resolution (fine scale). The coarse-scale observations were tested using both conventional geostatistics and an application of a time-series technique (Runs test) for scale of seagrass cover contiguity. Fine-scale observations were examined using conventional geostatistics and a least squares approach (cumulative logistic). The coarse-scale observations revealed little scale dependency and indicated that the structure was organized at spatial extents finer than our sample spacing; the cumulative logistic technique revealed potential fine-scale patterns not otherwise discerned. In contrast, surveys of the 10 x 10 m quadrats detected strong scale dependency with multiple small gaps, indicating scale-dependent patterns arising from processes operating at extents generally < 14 m. Between June and October 1999, a Category I hurricane passed over the study area, rearranging large areas of sand that uncovered some rocky hard bottom areas, while covering others; by the next growing season the newly covered areas were vegetated with Halophila decipiens that likely arose from transported seeds. Spatial analysis revealed that the storm led to a shift to greater frequency of H. decipiens, but lower density coverage. Seagrass density remained substantially depressed in all areas a full year following the storm. The short life history of H. decipiens and the apparent existence of a moveable seed bank means that spatial organization of this community is dictated first by large-scale dispersal of plant propagules (hundreds of meters) and then within a growing season, by clonal organization of the seagrass operating over very small distances (m). The two techniques (semivariance and Runs test) led to similar conclusions regarding the organizational scales of seagrass landscape pattern. As with terrestrial examples, this study demonstrates the importance of selecting the appropriate scale for detection of landscape pattern and processes influencing population ecology of a seagrass ecosystem. Published by Elsevier Ltd.