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首页> 外文学位 >Effects of Hydrology and Livestock Use on Modoc Plateau Vernal Pool Region Plant Communities.
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Effects of Hydrology and Livestock Use on Modoc Plateau Vernal Pool Region Plant Communities.

机译：水文和牲畜使用对Modoc高原春季池区植物群落的影响。

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摘要

Vernal pools are unique ecosystems that serve as ephemeral wetlands in Mediterranean climates and contain a great number of endemic plant species specially adapted to vernal pool hydrologic regimes. Vernal pool plant communities are distributed along inundation gradients, created by basin microtopography, depending on individual species habitat requirements. Vegetation in pool basins is dominated by native annual plant species that can tolerate the disturbance created by fluctuating hydrology. Another form of disturbance experienced in vernal pools is livestock grazing which has been part of the California landscape for over 150 years. My research examined the effects of these two disturbance processes on vernal pool plant communities and quantified how one endemic vernal pool specialist plant, Orcuttia tenuis, responded to gradients of hydrology and livestock use.;In the first chapter, I examined hydrologic influences on vernal pool plants in two vernal pools located within the Modoc Plateau Vernal Pool Region. I utilized multivariate analyses to identify five vernal pool plant community types and determine how communities responded to maximum depth and inundation length. The five community groups were defined as edge, short-term inundated, long-term inundated, shallow tolerant, and deep tolerant depending on indicator species for each group and tolerance to hydrologic thresholds. My findings revealed a community group characterized by longer inundation periods than had previously been reported for California vernal pools. I also utilized generalized linear models and ordinal regression analyses to estimate favorable hydrologic conditions for O. tenuis occurrence, abundance, height, and spikelet density. My findings indicate likelihood of occurrence, abundance, height, and spikelet density increased with increasing maximum depth and inundation length with no upper threshold for this response.;In the second chapter, I examined how livestock use and environmental metrics affect vernal pool plant community structure and O. tenuis . This study utilized data collected over a three year period from 2009 to 2011 from twenty O. tenuis populations occurring in vernal pools. I utilized multivariate analysis to examine vernal pool plant community structure along ecological gradients defined by the physical environment and livestock use. Responses of O. tenuis population characteristics to livestock use were modeled with quantile regression and generalized linear mixed effects models. Livestock use and grazing intensity were not significantly associated with vernal pool plant community structure; however, both variables had negative associations with O. tenuis population characteristics including presence and height. High intensity grazing had a stronger negative relationship with O. tenuis responses than low intensity grazing. These analyses at the level of individual 1m2 quadrats suggest that livestock use may not be beneficial for O. tenuis conservation and recovery, but further investigations are needed to explore O. tenuis responses to alternative grazing management scenarios at the population level.;Overall, my research aims to clarify the complex processes occurring in Modoc Plateau vernal pools and has significant implications for the management and recovery of sensitive vernal pool plant species. The novel methodology utilized in this study, incorporating remote photography, field surveys, and topographic relief modeling, will be valuable in ecosystems experiencing similar climatic conditions or monitoring limitations. My results also highlight the importance of using continuous metrics of livestock grazing intensity in exclosure studies. The findings contribute to a better understanding of vernal pool ecology and offer insight into potential hydrologic restoration of vernal pool habitat.
机译：春季池是独特的生态系统，在地中海气候中是短暂的湿地，并且包含大量特别适合春季池水文状况的特有植物物种。春季池植物群落沿着淹没梯度分布，这取决于盆地的微地形，具体取决于单个物种的栖息地要求。池盆中的植被主要由一年生的原生植物组成，这些物种可以忍受水文波动造成的干扰。春季池中发生的另一种干扰形式是放牧牲畜，这已经成为加利福尼亚地区150多年来的一部分。我的研究检查了这两种干扰过程对春季池植物群落的影响，并量化了一种地方性春季池专业植物Orcuttia tenuis如何应对水文和牲畜使用梯度。在第一章中，我研究了水文对春季池的影响。在Modoc Plateau春季池区域内的两个春季池中种植植物。我使用多变量分析来确定五种春季游泳池植物群落类型，并确定群落如何响应最大深度和淹没长度。根据每个组的指示物种和对水文阈值的容忍度，将五个群落组定义为边缘，短期淹没，长期淹没，浅层耐受和深层耐受。我的发现揭示了一个社区群体，其淹没时间比以前报道的加利福尼亚州的春季池长。我还利用广义线性模型和有序回归分析来估计O. tenuis发生，丰度，高度和小穗密度的有利水文条件。我的发现表明发生的可能性，丰度，高度和小穗密度随最大深度和淹没长度的增加而增加，而对此响应没有上限。在第二章中，我研究了牲畜的使用和环境指标如何影响春季池植物群落结构和O. tenuis。这项研究利用了从2009年到2011年这三年期间从春季池中出现的二十个O. tenuis种群中收集的数据。我利用多变量分析来检查沿物理环境和牲畜使用所定义的生态梯度的春塘植物群落结构。用分位数回归和广义线性混合效应模型对O. tenuis种群特征对牲畜使用的响应进行建模。牲畜的使用和放牧强度与春季池植物群落结构没有显着相关。然而，这两个变量都与O. tenuis种群特征（包括存在和高度）呈负相关。与低强度放牧相比，高强度放牧与ten.us响应具有更强的负相关性。这些在单个1平方公尺土地面积上的分析表明，牲畜的使用可能不利于ten.us的保存和恢复，但是还需要进一步调查以探索ten.us对种群一级替代放牧管理方案的反应。这项研究旨在弄清Modoc Plateau春季池中发生的复杂过程，并对敏感的春季池植物物种的管理和恢复具有重要意义。这项研究中使用的新颖方法，结合了远程摄影，野外调查和地形起伏模型，将在经历类似气候条件或监测限制的生态系统中具有重要价值。我的结果还强调了在放牧研究中使用牲畜放牧强度的连续指标的重要性。这些发现有助于更好地理解春季池生态系统，并为春季池生境的潜在水文恢复提供见识。

著录项

  • 作者

    Gosejohan, Meredith C.;

  • 作者单位

    University of Nevada, Reno.;

  • 授予单位 University of Nevada, Reno.;
  • 学科 Biology Botany.;Biology Ecology.
  • 学位 M.S.
  • 年度 2012
  • 页码 130 p.
  • 总页数 130
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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