Effects of climate-driven species change on forest carbon and nitrogen cycling

关于气候变化对森林影响的大多数研究都集中在预测的温度和降水变化的直接影响上。然而，很明显，除了气候对森林生态系统功能的直接影响外，气候驱动的树种组成变化也会造成间接影响。随着气候变暖，北美树种的分布范围将逐渐向北移动。在任何给定的地点，这将产生树种的变化，有利于那些适应温暖气候的物种。由于树种在许多方面都是独一无二的，物种组成的变化将改变森林生态系统的功能。大多数预测气候变化对森林影响的计算机模型都没有包括这种物种变化。这项研究将填补这一空白，方法是将两个独立的计算机模型与一个预测树种范围将如何随着气候变化而变化的统计模型和一个预测物种变化对森林功能关键方面（如生产力、碳储存和氮循环）的影响的模拟模型联系起来。这些相关联的模式将用于预测气候变化对下个世纪几种气候变化现实情景下森林功能的影响。最初的努力主要集中在美国东北部，但如果有足够的关于最重要树种特征的信息，这种方法和模型可能适用于整个国家，甚至全世界的森林。该项目是加里生态系统研究所和美国农业部林业局共同努力的结果。这项研究将对研究气候变化的科学界产生重大影响，因为它将把注意力集中在一个重要但经常被忽视的问题上，即树种组成的变化如何影响森林的功能和恢复力。此外，这显然是一个与政策相关的问题，对东北森林流域的森林生长、生物多样性、碳封存和空气污染产生的氮的保留等问题都很重要。加里研究所和林务局的主要研究人员将使这项研究的结果可供决策者、自然资源管理者和一般公众使用。研究结果，包括模型结果的技术细节，将在由项目工作人员维护和支持的网站上提供。本项目建立的模型将有助于分析全球变化的其他重要问题，包括由非本地虫害和病原体的引入和非本地植物的入侵引起的树种变化。该项目还将支持1名博士后和2名本科生的教育机会。

Most studies of the effects of climate change on forests have focused on the direct effects of predicted changes in temperature and precipitation. However, it is clear that in addition to the direct effects of climate on the functioning of forest ecosystems, there will also be indirect effects caused by climate-driven changes in tree species composition. As the climate warms, the ranges of North American tree species will gradually shift northward. At any given location, this will produce a change in tree species, favoring those species adapted to warmer climates. Because tree species are unique in many different ways, the change in species composition will alter the functioning of the forest ecosystem. This species change is not included in most computer models that predict the effects of climate change on forests. This study will fill that gap by linking two separate computer models with a statistical model that predicts how the ranges of tree species will shift as the climate changes, and a simulation model that predicts the effects of the species change on key aspects of forest function such as productivity, carbon storage, and nitrogen cycling. The linked models will be used to forecast the effects of climate change on forest functioning for several realistic scenarios of climate change over the next century. This initial effort is focused on the Northeastern U.S., but the approach and the models are potentially applicable to forests throughout the country, and even throughout the world, if sufficient information is available about the characteristics of the most important tree species. This project is a collaborative effort involving the Cary Institute of Ecosystem Studies and the USDA Forest Service.This research will have significant impacts on the scientific community studying climate change by focusing attention on the important, but often ignored, issue of how changes in tree species composition will affect the functioning and resillience of forests. In addition, this is clearly a policy-relevant question that is important for issues of forest growth, biodiversity, carbon sequestration, and retention of air pollution-derived nitrogen in forested watersheds in the Northeast. The principal investigators from the Cary Institute and the Forest Service will make the results of this research available and accessible to policy makers, natural resource managers, and the general public. The results of the study, including the technical details of the model results, will be available on web sites that will be maintained and supported by project staff. The models developed in this project will be useful for analysis of other important issues of global change, including tree species change caused by introductions of non-native insect pests and pathogens and by invasions of non-native plants. This project will also support educational opportunities for one postdoctoral associate and two undergraduate students.