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首页> 外文学位 >The role of biotic and abiotic processes in the zonation of salt marsh plants in the Nueces River Delta, Texas.
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The role of biotic and abiotic processes in the zonation of salt marsh plants in the Nueces River Delta, Texas.

机译：生物和非生物过程在德克萨斯州Nueces河三角洲盐沼植物分区中的作用。

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摘要

Salt marshes provide critical ecosystem services, such as shoreline stabilization, biogeochemical cycling and habitat for wildlife, to much of the world's population living on the coasts. Emergent vascular plants are a critical component of these ecosystems. This study was a comprehensive effort to gain a better understanding of the ecology of salt marsh plants in the Nueces River delta on the south Texas coast. This knowledge is essential to understand the potential anthropogenic impacts on salt marshes, including sea-level rise, global warming, reduced freshwater inflow and coastal erosion. A combination of remote sensing analysis, field studies and experiments were used to allow analysis across spatial scales ranging from landscape patterns of vegetation to leaf level measurements of the dominant species. A novel method of image classification was developed using high-resolution multi-spectral imagery integrated with ancillary data to map the major plant communities at a landscape scale. This included a high marsh assemblage composed primarily of Spartina spartinae and a low marsh community dominated by Borrichia frutescens and Salicornia virginica. Geospatial analysis determined that the location of these plant communities was related to the distance from the tidal creek network and elevation. The B. frutescens and S. virginica assemblage was more abundant at lower elevations along the waters edge, making it vulnerable to loss from shoreline erosion.;At a finer spatial scale, gradient analysis was utilized to examine the relationship between elevation, which creates environmental gradients in salt marshes, and species distribution. I discovered that elevation differences of less than 5 cm can influence both individual species and plant community distribution. One interesting finding was that the two dominant species, B. frutescens and S. virginica, share similar responses along an elevation gradient yet are observed growing in monotypic adjacent zones. I constructed a large reciprocal transplant experiment, using 160 plants at 4 sites throughout the marsh, to determine what causes the zonation between these two species. The results of this study found that S. virginica fared well wherever it was transplanted but was a weak competitor. B. frutescens survival was significantly lower in the S. virginica zone than in its own zone suggesting that abiotic factors are important in determining the zonation of this species. However, high spatial and temporal variability existed in environmental parameters such as salinity. This variability may have been caused by the semi-arid climate and irregular flooding typical in the Nueces Marsh. Therefore, I utilized a greenhouse experiment to directly test the importance of the two dominant physical factors in salt marshes, flooding and salinity. The results found that for B. frutescens the effects of flooding were not significant, however salinity at 30‰ reduced growth. Salinity did not influence growth of S. virginica. The greater ability of S. virginica to tolerate salinity stress has important implications because reduced freshwater inflow or climate change can increase porewater salinity, thus favoring the expansion of S. virginica, and altering the plant community structure.
机译：盐沼为世界上许多沿海地区的人口提供了至关重要的生态系统服务，例如海岸线稳定，生物地球化学循环和野生生物栖息地。新生的维管植物是这些生态系统的关键组成部分。这项研究是一项全面的工作，目的是为了更好地了解德克萨斯州南部海岸Nueces河三角洲的盐沼植物的生态。该知识对于了解对盐沼的潜在人为影响至关重要，包括海平面上升，全球变暖，淡水流入减少和海岸侵蚀。结合了遥感分析，野外研究和实验，可以跨空间尺度进行分析，范围从植被的景观模式到优势物种的叶面测量。利用高分辨率多光谱图像和辅助数据开发了一种新的图像分类方法，以景观尺度绘制主要植物群落。其中包括一个主要由斯巴达斯草（Spartina spartinae）组成的高沼泽组合，以及一个由弗氏疏螺旋体（Borrichia frutescens）和弗吉尼亚州柳柳（Salicornia virginica）主导的低沼泽群落。地理空间分析确定这些植物群落的位置与距潮汐河网的距离和海拔高度有关。沿水域低海拔处的弗氏芽孢杆菌和维吉尼亚链霉菌组合较多，使其容易遭受海岸线侵蚀的损失。；在更精细的空间尺度上，利用梯度分析来检验海拔之间的关系，从而创造了环境。盐沼中的梯度和物种分布。我发现高度差小于5 cm会影响单个物种和植物群落分布。一个有趣的发现是，两个优势种，弗氏芽孢杆菌和维京葡萄球菌，沿海拔梯度具有相似的响应，但观察到在单型相邻区域中生长。我建立了一个大型的互惠移植实验，在整个沼泽地的4个地点使用160株植物，以确定是什么原因导致了这两个物种之间的分区。这项研究的结果发现，无论在何处移植，S。virginica都表现良好，但竞争能力很弱。弗氏链球菌在维吉尼亚链霉菌区的存活率明显低于其自身区，这表明非生物因素在确定该物种的区划中很重要。然而，诸如盐度的环境参数中存在高的时空变异性。这种变化可能是由于Nueces Marsh中典型的半干旱气候和不规则洪水造成的。因此，我利用温室实验直接测试了两个主要物理因素在盐沼，洪水和盐度中的重要性。结果发现，对于弗氏芽孢杆菌，浸水的影响不明显，但是盐分在30‰时会降低生长。盐度不影响弗吉尼亚链霉菌的生长。由于减少的淡水流入量或气候变化会增加孔隙水的盐度，因此弗吉尼亚州链霉菌具有更高的耐盐胁迫能力，这具有重要意义，这有利于弗吉尼亚州链霉菌的扩展，并改变了植物群落结构。

著录项

  • 作者

    Rasser, Michael Kevin.;

  • 作者单位

    The University of Texas at Austin.;

  • 授予单位 The University of Texas at Austin.;
  • 学科 Biology Botany.;Biology Ecology.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 166 p.
  • 总页数 166
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-17 11:38:31

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