气候变化、林火和采伐对大兴安岭森林与土壤碳储量的长期影响

For the past two decades, the complex interactions and coupled effects among landscape progresses under climate change on forest and soil carbon storage and long-term dynamics has become a focal area of global warming effects and human mitigation strategies research in the international scientific community. Much progress has been made internationally; however, the research in China in this key research area has been slow due to data scarcity and the limitation on certain critical technologies. There have been projects on forest carbon storage and carbon cycles, but most of them are only focused on about ground forest vegetation carbon pools at the national scale. As a result resolution is coarse and estimates of the carbon pools are with higher uncertainty. Even few projects have examined long-term, coupled effects of landscape progresses and climate change that combines both aboveground forest and underground soil carbon in details. We propose to study the long-term, coupled effects among landscape progresses (e.g., wildfires, harvest, and management practices) and climate change on both forest and soil carbon dynamics, by using field survey data and proven forest landscape and disturbance model (LANDIS-II). The study region will be the Greater Xing'an Mountain region, where has been the most important forest timber production in the past and current the key area for carbon sink in China. This proposed project will provide more accurate estimates of existing total carbon storage for the study region and the temporal and spatial pattern of carbon dynamics for the future under the projected climate change from IPCC. This research could provide scientific base for a sustainable forestry regional planning and to help to establish a health carbon credit market in the region.

气候变化、林火与采伐等景观过程的耦合作用及其长期影响是目前全球变化和碳科学计划研究的焦点之一。我国在这一领域的研究具有了良好基础，但对气候变化下林火与采伐等景观过程之间的耦合效应及其长期影响研究还待深入，特别应加强对碳估算不确定性的分析和评价。本项目采用多模型集成和模型-数据融合的方法，选择对气候变化敏感的大兴安岭森林生态系统为研究对象，在多个气候变化情形下，同时模拟和预测（地上）森林与（地下）土壤碳库的变化趋势，并提供结果不确定性的定量评估。在理论上，探索大兴安岭森林在气候变化下的碳储量变化的时空规律及其与林火与采伐、造林等人为活动影响耦合效应的机制。对阐明气候变化对北方森林和土壤固碳效应的机制，深化对北方森林对气候变化的响应机制和碳储量变化规律有重要意义。实践意义在于可服务大兴安岭林区林业管理，为森林固碳及生态系统服务功能的恢复和减缓气候变化的不利影响提供科学依据。

选择大兴安岭林区为研究区，利用森林景观模型技术手段定量评估和预测了气候变暖情形下森林生态系统碳储量的长期变化趋势和范围。结果表明在当前气候条件和火干扰状态不变的情形下, 目前的单优势树种兴安落叶松继续占据优势树种地位，区域碳储量总值持续增加；未来气候（变暖）和火干扰状态不变情景下, 区域碳储量总值持续增幅加大，耐寒的兴安落叶松和偃松的碳储量降低,而白桦、山杨、甜杨和钻天柳等阔叶树以及樟子松的碳储量增加；气候变暖有利于大部分喜暖树种的生长,不利于耐寒的兴安落叶松和偃松的碳储量积累。未来气候（变暖）和火频率增大时，区域碳储量总值增幅减缓。气候变化和火干扰的双重作用会使大兴安岭森林的碳汇作用减弱。研究发现气候变暖对森林碳储量的影响具有长期性和时滞性。火干扰增加对森林景观的影响与气候变化的直接影响同等重要。采伐是影响兴安落叶松和白桦树碳储量变化的主要因素，对处于建群阶段（0-40 年）和老龄阶段（>180 年）的树种碳储量变化有显著影响。这些结果为森林动态分析技术、林业可持续发展政策提供空间变化分析工具，为区域碳储量的核算和变化幅度提供技术支持。