Collaborative Research: Controls on the Isotopic Composition of Fixed CO2 and Ecosystem-Respired CO2 in Southeastern Pine Forests

自从科学家将人类产生的二氧化碳与全球变暖联系在一起以来，他们一直试图量化人类对气候的影响程度。人类产生的二氧化碳的一半--主要来自化石燃料的燃烧--仍然留在大气中。另一个“缺失的一半”要么被海洋吸收，要么在光合作用期间被陆地植物吸收。要了解人类活动如何影响全球气候和全球碳循环，了解有多少资金流向哪里是至关重要的一环。追踪二氧化碳去向的一个有用的标志是空气中二氧化碳中13C与12C的比率。陆地植物优先吸收12C，丰富了13C的空气。海洋在吸收二氧化碳时不会有区别。因此，通过测量13C和12C的比率，科学家可以判断二氧化碳是进入陆地植物还是进入海洋。但是，陆地植物在13C到12C之间的吸收程度存在差异，因此预测人类产生的二氧化碳最终流向哪里的模型可能会有很大误差。为了限制误差，并更好地估计二氧化碳的命运，将进行一项新的研究，以检查南部松林，北美最大的碳汇之一。这项研究将着眼于气候变化如何影响植物在呼吸过程中吸收和释放的二氧化碳的13C/12C比率。这一结果可能会对陆地植物作为人类产生的二氧化碳的“汇”的重要性进行重大的重新计算。这项研究将着眼于树叶蜡和呼吸的二氧化碳中的碳同位素组成。这将被用来改进对陆地碳汇分布和大小的估计，这是进一步了解陆地植物作为人类产生的二氧化碳吸收者的重要性的一步。

Ever since scientists linked human production of carbon dioxide with global warming, they have sought to quantify how much impact humans have had on climate. Half the CO2 produced by humans-mainly from the burning of fossil fuels-remains in the atmosphere. The other "missing half" is either adsorbed by the oceans or taken up by terrestrial plants during photosynthesis. Knowing how much goes where is a crucial link in understanding how human activity affects global climate and the global carbon cycle. A useful marker to trace the destination of CO2 is the ratio of 13C to 12C in CO2 in the air. Land plants preferentially take up 12C, enriching the air in 13C. The oceans don't discriminate when they take up CO2. So by measuring the ratio of 13C to 12C, scientists can tell whether the CO2 is going into land plants or into the ocean. But there is variation in how much 13C to 12C land plants take up, so the models that predict where human-produced CO2 winds up can have significant error. To limit the error, and develop better estimates of the fate of CO2, a new study will be conducted to examine southern pine forests, one of the largest carbon sinks in North America. The study will look at how climate variability affects the 13C/12C ratio of the CO2 that plants absorb and release during their respiration. The result may yield a significant recalculation of how important land plants are as a "sink" for human-produced CO2.The study will look at carbon isotope composition in leaf waxes and respired CO2. This will be used to improve estimates of the distribution and magnitude of the terrestrial carbon sink, a step in further understanding the importance of land plants as absorbers of CO2 produced by humans.