Ecological relevance of carbon isotope fractionation during dark respiration

对生物圈/大气二氧化碳交换的功能性理解对于全球气候变化很重要。因此，生态系统同化和呼吸通量及相关碳库的研究已成为全球生态系统研究的主要目标。稳定的碳同位素比率δ13C提供了一个强大的诊断工具，以确定驱动生态系统呼吸过程的潜在机制。植物暗呼吸过程中的同位素分馏已经在生理尺度上得到了透彻的理解，但对其在更大尺度上的影响却知之甚少。很明显，这种分级的程度在不同的功能植物群中有很大的不同，但对其机理的实验证据仍然缺乏。该项目旨在通过结合代谢、全植物和生态系统的方法，弥合暗呼吸中分馏的最新进展、机制及其生态学意义之间的差距。这项研究将重点分析呼吸δ13Cres在特定功能群中的短期变化，并考虑叶、地上部和根中代谢物库的日动态。将通过在天然地中海生态系统中使用成分质量平衡方法评估至少全植物和生态系统规模的过程，来评估δ13Cres在较大尺度上的日动态的可能影响。了解生态系统呼吸δ13C动态变化背后的过程对于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.