Local and nonlocal topographic controls on landscape ecohydrology

本研究的总体目标是统计量化在不同水文气候强迫和地质年龄的复杂地形中，局部与非局部地貌控制对景观代谢的相对重要性，以及它们的非线性程度和阈值效应的量化。本研究的指导思想是，局部和非局部地形效应对景观代谢的相对重要性随着水文气候条件的变化而变化。此外，这种变化的条件随着景观年龄和相关的表面平滑过程而变化，这改变了地形属性分布（坡向、坡度、贡献面积等）的相对重要性。该研究将利用统计场理论对景观进行理论描述，并分析CN循环（辐射、土壤特征、植被覆盖和土壤水分动态）的局部和非局部控制。最后，它将局部和非局部控制耦合到生物地球化学动力学中，扩展以前的随机土壤湿度和生物地球化学模型，以包括空间随机成分。控制植被和土壤养分动态及其相关碳氮通量（也称为景观代谢）的基本环境过程与土地能量和水收支有关。本研究分析了这些过程，并量化了它们在空间和时间上的差异，作为局部和非局部景观特征（如坡度、朝向和排水面积）的函数。这一建议将为更基本地理解河流流域和山区等复杂景观中不同空间尺度的碳、氮和水通量规律铺平道路。该项目将有助于量化全球气候模式的陆地表面条件，特别是在气候和土地利用情景变化的背景下。

The overarching goal of this research is the statistical quantification of the relative importance of local vs. nonlocal geomorphologic controls on landscape metabolism in complex topographies differing in hydroclimatic forcing and geologic age, and the quantification of their degree of nonlinearity and threshold effects. The research is guided by the hypothesis that the relative importance of local and nonlocal topographic effects on landscape metabolism shifts according to hydroclimatic conditions. Moreover, the conditions for such shifts change with the landscape age and the related surface smoothing processes, which modify the relative importance of tails vs. mode of the distributions of topographic properties (aspect, slope, contributing area, etc.). The research will provide a theoretical description of landscapes using statistical field theories, and analyze local and nonlocal controls on CN cycles (radiation, soil features, vegetation cover, and soil moisture dynamics). Finally it will couple local and nonlocal controls to biogeochemical dynamics, extending previous stochastic soil moisture and biogeochemistry models to include spatially random components. The fundamental environmental processes controlling vegetation and soil nutrient dynamics and the related carbon and nitrogen fluxes (also called landscape metabolism) are related to the land energy and water budgets. This research analyzes such processes and quantifies how they differ in space and time, as a function of the local and nonlocal landscape features, such as slope, orientation and drainage area. This proposal will pave the way to a more fundamental understanding of the laws for carbon, nitrogen, and water fluxes at different spatial scales over complex landscapes such as river basins and mountain regions. The project will be instrumental for the quantification of the land surface conditions for global climate models, especially in the contexts of variation in climatic and land-use scenarios.