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首页> 外文学位 >Biological nitrogen fixation in tropical dry forests of Costa Rica: Patterns and controls.
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Biological nitrogen fixation in tropical dry forests of Costa Rica: Patterns and controls.

机译：哥斯达黎加热带干旱森林中的生物固氮：模式和控制。

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摘要

In tropical forests, new nitrogen (N) inputs fuel a large proportion of global net primary productivity. However, global estimates of tropical N fixation are biased towards wet forests and other areas such as tropical dry forests are understudied. In the dry forests of Guanacaste, Costa Rica, N fixing legume trees are highly abundant throughout forest successional stages, thus I hypothesized that in tropical dry forests legume trees are critical regulators of ecosystem level N dynamics. I addressed this question from multiple approaches that included a shade house experiment and field surveys of N fixing legume trees in plantations or in diverse secondary forests using a common set of species: Acosmium panamense, Dalbergia retusa, Enterolobium cyclocarpum, Gliricidia sepium, and Lysiloma divaricatum. Individual legume species had measurable influences on a number of soil properties, but this effect is more pronounced than the influence of legumes as a functional group. I observed species-specific variation in belowground foraging strategies and in the timing and degree of nodulation. In the shade house experiment, species differed in their nodulation effort and in how they regulated N fixation with respect to available resources. These five legume species could be arrayed along a continuum defined by strategies of nutrient conservation and nutrient acquisition, which coincided with degrees of fine-tuning of N fixation. In the field study, I did not find evidence of down-regulation of fixation with soil N. I hypothesized that the adjustment of N fixation to soil nutrients occurs indirectly and is mediated by water availability and its effects on nutrient pulses. My stand-level estimates N fixation by legumes showed that legumes are responsible for the largest contribution of new N inputs to this ecosystem relative to other inputs such as free-living fixation or wet deposition, but which are modest relative to N recycling through leaf litter and fine root decomposition. Different legume strategies could represent different ways of dealing with the transient and seasonal water availability of this ecosystem. Collectively, my results suggest that the conceptual models of how N fixation works in tropical wet forests may not necessarily be the same in seasonally dry forests.
机译：在热带森林中，新的氮（N）投入为全球净初级生产力的很大一部分提供了燃料。但是，全球对热带固氮的估计偏向于湿润的森林，而对其他地区（如热带干旱森林）的研究却不足。在哥斯达黎加瓜纳卡斯特的干旱森林中，整个森林演替阶段固氮豆科植物非常丰富，因此我假设在热带干旱森林中，豆科树木是生态系统氮水平动态的关键调节因子。我通过多种方法解决了这个问题，其中包括进行遮荫棚实验以及对种植园或不同次生林中使用固定物种的N种固定豆科植物树木进行田间调查，这些物种包括以下一组常见物种：Acosmium panamense，Dalbergia retusa，Enterolobium cyclocarpum，Gliricidia sepium和Lysiloma divaricatum 。单个豆类物种对许多土壤特性都有可测量的影响，但这种影响比豆类作为功能基团的影响更为明显。我观察了地下觅食策略以及结瘤的时间和程度中特定物种的变化。在遮荫棚实验中，物种的结瘤作用以及在调节可用资源方面对固氮的调节方式有所不同。这五种豆科植物可以沿着由养分保存和养分获取策略定义的连续体排列，这与固氮的微调程度相吻合。在田间研究中，我没有发现土壤固氮作用下调的证据。我假设对土壤养分的固氮作用是间接发生的，并且受水分利用及其对养分脉动的影响。我的标准水平估计，豆类固氮作用表明，豆科植物相对于其他输入（如自由固定或湿沉降）对生态系统的新氮输入贡献最大，但相对于通过凋落物回收氮而言，这是适度的和细根分解。不同的豆科植物策略可能代表处理该生态系统的瞬态和季节性水可利用性的不同方式。总的来说，我的结果表明，在热带湿林中固氮作用原理的概念模型在季节性干旱森林中可能不一定相同。

著录项

  • 作者

    Gei, Maria Gabriela.;

  • 作者单位

    University of Minnesota.;

  • 授予单位 University of Minnesota.;
  • 学科 Biology Ecology.;Environmental Management.;Natural Resource Management.;Agriculture Forestry and Wildlife.;Biology Conservation.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 236 p.
  • 总页数 236
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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