NSF Postdoctoral Fellowship in Biology FY 2017: Reconstructing CO2 fertilization with herbaria

这是NSF生物学博士后研究奖学金，项目是使用生物收藏进行研究。这位名叫利安德·安德罗格的研究员正在进行研究，并接受以创新方式利用生物收藏的培训，并由两家主办机构的两名赞助科学家提供指导：托德·道森(加州大学伯克利分校)和约瑟夫·贝里(卡内基科学研究所)。这位研究员正在研究植物在过去一个世纪里如何应对大气中不断上升的二氧化碳(CO2)，以预测未来植物将如何应对人类不断增加的二氧化碳排放。植物就像商人：它们本质上是将水交易到大气中，以换取通过光合作用生产糖所需的二氧化碳。通过燃烧化石燃料，人类改变了全球碳-水交换率，使从大气中购买二氧化碳变得更便宜，从而有利于植物。从理论上讲，这可以促进世界各地的植物生长，提高作物产量，并增加我们的生态系统未来可以从大气中吸收多少二氧化碳排放。然而，最近的观察表明，这种二氧化碳施肥效应比之前认为的要有限得多，变化也更大。这项研究探索了为什么二氧化碳施肥反应如此复杂，重点是干旱胁迫和植物物种之间的差异如何决定一种植物是否以及如何对大气二氧化碳上升做出反应。该研究人员使用了来自博物馆植物标本馆收藏的百年植物样本以及从相同地点收集的现代样本来重建加州各地的树木物种如何对二氧化碳上升做出反应。这位研究员正在比较这些历史和现代树叶的形态、解剖和化学成分，以确定在过去的一个世纪里，树木如何改变了它们的生理。通过这项研究收集的植物对二氧化碳反应的历史和当代记录也揭示了二氧化碳施肥如何因物种和气候而异。这位研究员正在利用这些信息，以及根据树心和机械光合作用模型重建的树木生长，来了解水分供应和物种生理如何决定树木对二氧化碳浓度升高的反应。这项工作有助于协调短期二氧化碳施肥实验的结果和树木年轮对水和二氧化碳之间交换率的长期观察。对导致不同CO2施肥反应的植物特性和环境条件的细微差别的理解将提高我们在加速环境变化下预测陆地生态系统功能的能力。这位研究员正在接受植物解剖学、同位素和建模技术方面的培训，同时还在开发新的方法，从未得到充分利用的植物标本收藏中解锁关键信息。

This is an NSF Postdoctoral Research Fellowship in Biology, under the program Research Using Biological Collections. The fellow, Leander Anderegg, is conducting research and receiving training that utilizes biological collections in innovative ways, and is being mentored by two sponsoring scientists at two host institutions: Todd Dawson (University of California-Berkeley) and Joseph Berry (Carnegie Institute for Science). The fellow is investigating how plants have responded to rising amounts of carbon dioxide (CO2) in the atmosphere over the past century, in order to predict how plants will respond to increasing human CO2 emissions in the future. Plants are like merchants: they essentially trade water to the atmosphere in exchange for the CO2 they need to produce sugars through photosynthesis. By burning fossil fuels, humans have changed the global carbon-water exchange rate in plants' favor by making it less water-expensive to 'buy' CO2 from the atmosphere. Theoretically, this could increase plant growth around the world, improving crop yields and increasing how much of our CO2 emissions ecosystems can absorb from the atmosphere in the future. However, recent observations suggest that this CO2 fertilization effect is far more limited and variable than previously thought. This research explores why CO2 fertilization responses are so complex, focusing on how drought stress and differences between plant species determine if and how a plant responds to rising atmospheric CO2.The fellow is using hundred-year-old plant samples from museum herbarium collections along with modern samples collected from the same locations to reconstruct how tree species across California have responded to rising CO2. The fellow is comparing the morphology, anatomy and chemical composition of these historical and modern leaves to determine how trees have changed their physiology over the past century. The historical and contemporary records of plant responses to CO2 collected through this research are also revealing how CO2 fertilization varies across species and climates. The fellow is using this information, along with tree growth reconstructions from tree cores and mechanistic photosynthesis models, to understand how water availability and species physiology dictate tree responses to elevated CO2. This work is helping to reconcile the results of short-term CO2 fertilization experiments and long-term observations from tree rings of the exchange rate between water and CO2. A nuanced understanding of the plant traits and environmental conditions that lead to different CO2 fertilization responses will improve our ability to predict terrestrial ecosystem function under accelerating environmental change. The fellow is being trained in plant anatomical, isotopic and modeling techniques while also developing new methods for unlocking critical information from underused herbarium collections.