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首页> 外文学位 >Carbon and nutrient cycling in Pinus taeda L. and Pinus ponderosa Dougl. ex Laws. as affected by the belowground response to altered environmental conditions.
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Carbon and nutrient cycling in Pinus taeda L. and Pinus ponderosa Dougl. ex Laws. as affected by the belowground response to altered environmental conditions.

机译：taeda taeda L.和pinus pokerosa Dougl的碳和养分循环。前法律。受到地下环境条件变化的影响。

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Modern industrial society is effecting fundamental changes to the global cycles of carbon, nutrients and water. These changes are predicted to alter the Earth's climate and will have direct and indirect effects on net primary production. Small increases to plant production due to increased resource availability may offset CO{dollar}sb2{dollar} emissions from fossil fuel combustion, thereby acting as a negative feedback to anthropogenic climate change. The response of forest ecosystems to the changing environment is critical to our ability to predict the extent of the changes wrought by human activities. Of the processes regulating the flow of carbon and nutrients through forest ecosystems, belowground dynamics associated with roots are some of the most important, but least understood.; It is the purpose of this dissertation to shed light on several critical, but poorly studied aspects of root biology with the goal of improving our ability to formulate complete carbon and nutrient budgets for two important forest ecosystems of the United States: loblolly and ponderosa pine. Emphasis is placed on root growth, tissue quality, and decomposition as a function of changing the environmental factors of atmospheric CO{dollar}sb2,{dollar} nitrogen availability, water availability and temperature to levels projected from recent general circulation models or studies of trends in production (i.e. of reactive nitrogen). I achieved my goal by working on several collaborative projects supported by grants to investigate the effects of predicted global change on forest ecosystems. Both greenhouse and field studies were combined in an effort to determine the applicability of scaling results from highly controlled environments to actual field conditions.; I found that under growth conditions simulating those predicted for the future, both loblolly and ponderosa pine substantially increased biomass production resulting in larger root systems, hence potentially more carbon storage. Elevated CO{dollar}sb2{dollar} did not induce shifts in biomass partitioning as hypothesized by some authors, however shifts did occur as a result of temperature, nutrition, and water availability. The direction of the shifts was partially controlled by the ontogenetic stage of development of the plants and if they occur in nature, will probably be small in magnitude. Root tissue quality (concentrations of non-structural carbohydrates and macro-nutrients) did not change as a result of growth under elevated CO{dollar}sb2,{dollar} suggesting rates of belowground herbivory and decomposition will not be greatly altered in the future. A field experiment on the decomposition of roots under irrigation and fertilization showed little effect of either factor on mass loss rates, further supporting the view that belowground decomposition processes will be little affected by predicted changes to the environment.
机译：现代工业社会正在对碳，养分和水的全球循环产生根本性的变化。预计这些变化将改变地球的气候，并将对净初级生产产生直接和间接的影响。由于资源可利用性的增加，植物产量的小幅增长可能抵消了化石燃料燃烧产生的CO2排放，从而对人为气候变化产生了负面反馈。森林生态系统对不断变化的环境的反应对于我们预测人类活动造成的变化程度的能力至关重要。在调节通过森林生态系统的碳和养分流的过程中，与根相关的地下动态是最重要的，但鲜为人知。本文的目的是阐明根系生物学的几个关键但研究不足的方面，目的是提高我们为美国两个重要的森林生态系统（火炬松和美国黄松）制定完整的碳和养分预算的能力。重点放在根的生长，组织质量和分解上，以改变大气中CO，氮，水和温度的环境因素，使其达到最近的一般循环模型或趋势研究预测的水平生产中（即活性氮）。我通过参与多个由赠款支持的合作项目来实现我的目标，以研究预测的全球变化对森林生态系统的影响。温室和野外研究相结合，以确定从高度受控的环境到实际野外条件的结垢结果的适用性。我发现，在模拟未来预测的生长条件下，火炬松和美国黄松大大增加了生物量的产生，从而导致更大的根系，因此潜在地有更多的碳储量。如一些作者所假设的那样，升高的CO {sb2 {dollar}不会引起生物量分配的变化，但是由于温度，营养和水的利用而发生了变化。转移的方向部分地由植物的发育的发育阶段控制，如果它们发生在自然界中，其幅度可能很小。根组织质量（非结构性碳水化合物和大量营养素的浓度）没有因CO浓度升高而增长而改变，这表明地下草食动物和分解的速率将来不会有很大变化。在灌溉和施肥条件下对根的分解进行的田间试验表明，这两种因素对质量损失率的影响均很小，进一步支持了以下观点：地下分解过程几乎不受预计的环境变化的影响。

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