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首页> 外文学位 >Mechanisms of community, structural, and functional change by the generalist pathogen Phytophthora ramorum in California coast redwood forests.
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Mechanisms of community, structural, and functional change by the generalist pathogen Phytophthora ramorum in California coast redwood forests.

机译：加州沿海红木森林中的普通病原菌疫霉疫霉的群落，结构和功能变化的机制。

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摘要

Pathogens have been powerful forces shaping the composition and ecology of North American forests. Exotic pathogens have caused diseases such as chestnut blight, Dutch elm disease, and beach bark disease that altered forest community and canopy structure at the landscape scale. The pathogen Phytophthora ramorum is an exotic pathogen which causes the disease sudden oak death in California and Oregon forests. P. ramorum is a generalist with a broad host range however P. ramorum has disparate ability to sporulate or cause disease across hosts. In California forests, tanoak (Notholithocarpus densiflorus) supports sporulation and also rapidly develops disease. In contrast, several oak species (especially Quercus agrifolia) suffer mortality following infection but generally do not support sporulation. California bay laurel (Umbellularia californica ) is the most problematic of native host trees; this species supports high levels of sporulation but does not appear to have any deleterious impacts resulting from infection. In this dissertation I use six years of annual surveys across a network of 120 plots in redwood forests to understand the influences of community composition on disease dynamics and use these insights to determine the consequences of sudden oak death for community composition, canopy structure, and woody debris dynamics.;Infection in bay laurel has a 31% greater impact on tanoak mortality compared to infection in tanoak. The combination of greater killing power and the lack of deleterious impacts on bay laurel by the pathogen result in apparent competition between bay laurel and tanoak. This pattern is likely to increase bay laurel densities over time and thereby increase pathogen populations. The mortality rate of individual tanoak stems was also dependent on tree size with larger trees suffering more rapid mortality compared to small trees. Tanoak mortality was widespread in our study stands and we found no indirect evidence for pathogen resistance in our plot network however, P. ramorum infection only killed the above ground portion of infected tanoak in 43% of disease killed trees. The remaining trees develop prolific basal sprouts which are important in maintaining tanoak as a component of these forests. A combined epidemiological and population model for tanoak suggests that retention of tanoak is likely in many forests except those with very high bay laurel abundance and associated sporulation levels. In most cases tanoak will be removed from the overstory and, similarly to American chestnut, will become a species relegated to the forest understory. Stands with low densities of tanoak in a matrix of non-sporulation supporting species like Douglas-fir (Pseudotsuga menziesii) may reduce pathogen levels below those needed for disease outbreak and are potential refugia for overstory tanoak and associated ecosystem function. Some tanoak forests are likely to be protected due to geographic isolation, low densities of sporulation supporting species, or climate conditions outside the acceptable range for P. ramorum however, in most of the range of tanoak, extensive overstory mortality is likely in the coming century. The high likelihood of disease outbreak at the landscape level in combination with rapid mortality of large trees suggests a substantial pulse of carbon (C) may be released from California and Oregon forests over the course of this disease.
机译：病原体是影响北美森林组成和生态的强大力量。外来病原体引起了诸如栗叶枯萎病，荷兰榆病和海滩树皮病等疾病，这些疾病在景观尺度上改变了森林群落和冠层结构。致病疫霉是一种外来病原体，会导致该病在加利福尼亚州和俄勒冈州的森林中突然死亡。 P. ramorum是一个具有广泛宿主范围的通才，但是P. ramorum具有在宿主之间发芽或引起疾病的不同能力。在加利福尼亚州的森林中，tanoak（Notholithocarpus densiflorus）支持孢子形成并迅速发展疾病。相反，几种橡树种（尤其是非洲栎）在感染后会死亡，但通常不支持孢子形成。加州月桂树（Umbellularia californica）是当地寄主树中最成问题的。该物种支持高水平的孢子形成，但似乎不会因感染而产生任何有害影响。在这篇论文中，我使用了为期六年的年度调查，涵盖了120个红木林地，以了解社区组成对疾病动态的影响，并利用这些见解确定橡树猝死对社区组成，冠层结构和木质环境的影响。与塔诺克氏菌感染相比，月桂树感染对塔诺克氏菌死亡率影响大31％。更大的杀伤力和病原体对月桂树缺乏有害影响的结合导致月桂树和tanoak之间的明显竞争。随着时间的流逝，这种模式可能会增加月桂树的密度，从而增加病原体的数量。单独的tanoak茎的死亡率也取决于树的大小，与小树相比，大树的死亡率更高。 Tanoak死亡率在我们的研究林地中普遍存在，我们在小区网络中没有发现病原体抗药性的间接证据，但是，P。ramorum感染仅杀死了43％的病死树木中被感染tanoak的地面部分。其余的树木会长出大量的基础芽，这对于保持tanoak作为这些森林的组成部分非常重要。塔纳克病的流行病学和种群综合模型表明，除了具有极高月桂树丰度和相关孢子形成水平的森林外，许多森林中都可能保留塔纳克病。在大多数情况下，tanoak将被从树皮上移除，与美国栗子相似，将成为仅次于森林木皮的物种。在非孢子支持性物种如道格拉斯冷杉（Pseudotsuga menziesii）基质中具有低tanoak密度的林分可能会将病原体水平降低到疾病暴发所需的水平以下，并且可能是过高的tanoak和相关生态系统功能的潜在避难所。一些tanoak森林可能由于地理上的隔离，低密度的孢子支持物种或超出拉美假单胞菌可接受范围的气候条件而受到保护，但是，在大多数tanoak范围内，来年的过度耕种可能会导致死亡。 。在景观水平上疾病暴发的可能性很高，再加上大树的迅速死亡，表明在这种疾病过程中，加州和俄勒冈州森林可能释放出大量的碳（C）。

著录项

  • 作者

    Cobb, Richard Charles.;

  • 作者单位

    University of California, Davis.;

  • 授予单位 University of California, Davis.;
  • 学科 Biology Ecology.;Agriculture Plant Pathology.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 120 p.
  • 总页数 120
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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