Canopy cycling of carbon dioxide, water vapour and reactive trace gases: Measurement of fluxes and plan exological modelling

植被冠层吸收植物和/或其下土壤生物排放的痕量气体的能力最近被认为是痕量气体大气收支的一个重要方面。被吸收/逸出的痕量气体的量受以下因素控制：（a）植被和土壤的生理和/或表面特性;（B）湍流输送与痕量气体交换过程的相互作用;（c）湍流输送与大气化学变化的相互作用。在这方面，更好地了解冠层的解耦，植被和大气边界层之间的耦合是至关重要的。预计H2O和CO2或活性痕量气体（NO、NO²、O³、NH³、HONO、HNO³）的净垂直输送之间存在明显差异。因此，该分项目的目的是测量水通量和双向微量气体交换并建立模型，以及所涉过程的相互耦合;实验室研究补充了长期和非常规实地测量。土壤中的生物NO排放将通过实验室实验确定。在埃格的密集观测期间，将通过测量土壤空气剖面和土壤室来量化来自和流向土壤的通量。为了调查冠层内储存、冠层循环和整个生态系统交换的非活性和活性微量气体，将测量浓度的垂直分布以及冠层内和冠层上方活性微量气体的通量（通过涡度协方差和修正的鲍恩比技术）。在该模型中，冠层结构是由三维（不均匀）分布的个别植物，导致详细的（m尺度）的概率密度函数和冠层以下标量和通量。冠层内物质的再循环将通过将水蒸气的解耦方法（Penman-Monteith方程的重新表述）扩展到其他通量（例如，CO²、NO、NO²等）。在尺度放大过程中，地表非均匀性和去耦合对净通量的影响将通过以下方式包括在内：（a）求解埃格P3反应性痕量气体和植物生态学Meixner/Falge各自的方程，或者对参数分布进行解析，或者使用泰勒展开式，以及（B）基于详细的概率密度函数构建有效的一维模型参数化。

The ability of vegetation canopies to absorb trace gases, which are biogenically emitted by the plants and/or by the soil below, became recently known to be an important aspect of atmospheric budgets of trace gases. The amount of absorbed/escaping trace gases is controlled by (a) physiological and/or surface characteristics of vegetation and soils and (b) interaction of turbulent transport with processes of trace gas exchange, and (c) interaction of turbulent transport with atmospheric chemical transformations. In this respect, a better understanding of de-coupling of in-canopy layers, and coupling between vegetation and atmospheric boundary layer is of crucial importance. Distinct differences between the net vertical transport of H²O and that of CO² or reactive trace gases (NO, NO², O³, NH³, HONO, HNO³) are expected. Therefore, the sub-project aims at measuring and modeling of water fluxes and bi-directional trace gas exchange, as well as interactive coupling of the processes involved; long-term and campaign-wise field measurements are complemented by laboratory studies. Biogenic NO emission from soils will be determined by laboratory experiments. During EGER s Intensive Observation Periods, fluxes from and to soils will be quantified by measurements of the soil air profile and by soil chambers. For the investigation of in-canopy storage, canopy cycling, and whole ecosystem exchange of non-reactive and reactive trace gases vertical profiles of concentrations will be measured as well as in-canopy and above canopy fluxes of reactive trace gases (by eddy covariance and modified Bowen-ratio techniques). In the model, canopy structure is represented by 3D (inhomogeneous) distribution of individual plants, resulting in detailed (m-scale) probability density functions for in- and below canopy scalars and fluxes. In-canopy recycling of matter will be treated by extending the decoupling approach for water vapor (¿-reformulation of the Penman-Monteith equation) to other fluxes (e.g., CO², NO, NO², etc.). Effects of surface heterogeneities and de-coupling on net fluxes during the up-scaling process will be included by (a) solving the EGER P3 Reactive trace gases and plant ecology Meixner/Falge respective equations either analytically for the parameter distributions or using Taylor expansions, and (b) constructing effective 1D model parameterizations based on detailed probability density functions.