Ecological relevance of carbon isotope fractionation during dark respiration

对生物圈/大气CO2交换的功能性理解对于全球气候变化非常重要。因此，研究生态系统的同化和呼吸通量及其相关的碳库已成为世界范围内生态系统研究的主要目标。稳定碳同位素比值δ 13 C为识别生态系统呼吸过程的机制提供了有力的诊断工具。植物暗呼吸过程中的同位素分馏在生理尺度上已经有了全面的了解，但在更大尺度上的影响还知之甚少。很明显，这种分馏的程度在不同的功能植物群中有很大差异，但仍然缺乏关于机制的实验证据。本项目旨在通过结合代谢、全植物和生态系统方法，缩小暗呼吸分离机制及其生态学意义的最新进展之间的差距。本研究将重点分析呼吸δ 13 Cres的短期变化在选定的功能组考虑代谢物库在叶，茎和根的昼夜动态。在更大尺度上δ 13 Cres日动态的可能影响将通过在自然地中海生态系统中使用组分质量平衡方法评估整个植物和生态系统尺度上的过程来评估。了解生态系统呼吸δ 13 C的动态过程对评价生态系统对全球变化的响应具有重要意义。

A functional understanding of biosphere/atmosphere CO2 exchange is important regarding global climate change. Investigation of ecosystem assimilatory and respiratory fluxes and associated carbon pools has thus, become a major goal in ecosystem research world-wide. Stable carbon isotope ratios δ13C provide a powerful diagnostic tool to identify the underiying mechanisms driving ecosystem respiratory processes. A thorough understanding of isotopic fractionation during dark respiration in plants has been achieved on the physiological scale, however much iess is known about its impact at larger scales. It has become evident that the extent of this fractionation varies substantially among different functional plant groups but experimental proof on the mechanisms is still lacking. This project aims to close the gap between recent advances on,mechanisms of fractionation during dark respiration and its ecological significance by combining metabolic, whole-plant and ecosystem approaches. This study will focus on the analysis of short-term variations of respiratory δ13Cres in selected functional groups considering diurnal dynamics of metabolite pools in leaves, shoots and roots. Possible implications of diurnal dynamics in δ13Cres at larger scales will be assessed by evaluating the processes at the leat whole-plant and the ecosystem scale using a component mass balance approach in a natural Mediterranean ecosystem. Understanding the processes behind the dynamics of δ13C of ecosystem respiration has significant implications for the evaluation of ecosystem response to global change.