Dissertation Research: Modeling the Consequences of Heterogeneous Light Environments for Seedling Perfomance in Tropical Wet Forests: A Multi-Scale Approach

9701053查兹登这项建议解决了建立苗木对环境异质性变化模式的预测模型的迫切需要。PIS建议开发全植物碳收益的机制模型，该模型将与热带森林环境中与光异质性有关的植物表现的研究结合在一起。PIS将检测植物对光的自然时空变化的反应水平，以将叶片生理学与整个植物的结构、叶片展示和生物量分配相结合。该方法包括两个部分。首先，三种已知的耐荫树种的已知基因将沿着从林隙中心到林隙边缘和森林下层的连续可用光效梯度种植。将使用一个架构模型来衡量从叶片水平的光合作用测量到整个植物的碳收益估计。根据这些数据，PI将开发一个最大似然模型并将其参数化，该模型将整个植物的碳增量和生长作为光可获得性连续变化的函数。然后，该模型将被用来预测在次生林和乡土树木种植园中同一家系的移植苗木的生长，这两种生境类型的光可获得性模式不同。由于土地利用模式的变化会极大地影响光的空间和时间模式，这些信息将有助于理解和预测植物对当前和未来土地利用变化的反应。预测异质光环境对热带森林苗木种群的影响需要明确描述异质性的模式以及植物对这种异质性的反应模式。

9701053 Chazdon This proposal addresses the critical need to create predictive models of seedling response to changing patterns of environmental heterogeneity. The PIs propose to develop mechanistic models of whole-plant carbon gain that will be coupled with studies of plant performance in relation to light heterogeneity in tropical forest environments. The PIs will examine levels of plant response to natural spatial and temporal variation of light to integrate leaf physiology with whole-plant architecture, leaf display, and biomass allocation. The approach involves two components. First, known genotypes of three shade-tolerant tree species will be planted along a continuous gradient of light availability from the center of a gap, through gap edges, and into the forest understory. An architectural model will be used to scale from leaf-level measures of photosynthesis to whole-plant estimates of carbon gain. From these data the PIs will develop and parameterize a maximum likelihood model of whole-plant carbon gain and growth as a function of continuous variation in light availability. This model will then be used to predict growth of transplanted seedlings of the same family lines in secondary forest and native tree plantations, two habitat types differing in patterns of light availability. Since changing land use patterns can dramatically affect both spatial and temporal patterning of light, this information will help to understand and predict how plants may respond to current and future land use changes. Predicting the consequences of heterogeneous light environments for seedling populations in tropical forests requires an explicit characterization of the pattern of heterogeneity as well as patterns of plant response to this heterogeneity.