Understanding changes in vegetation productivity and carbon use efficiency and their responses to climate change is significant to accurately assess and predict regional carbon budget in Northeast forest area, a region being an important carbon sink and sensitive to global change. Based on MODIS monitoring data and vegetation type distribution data, I analyzed the spatiotemporal varia-tions of ecosystem productivity (net primary productivity (NPP), gross primary productivity (GPP)) and carbon use efficiency (NPP/GPP) of Northeast forest from 2000 to 2015. Results showed that the average NPP and GPP were 346.4 and 773 g C·m-2·a-1, respectively, and the average NPP/GPP was 0.45 during 2000 and 2015. NPP and GPP of different forest types were following the order: coniferous and broad-leaved mixed forests > deciduous broad-leaved forests > coniferous forests, while the difference in NPP/GPP was not significant among different forest types. NPP and GPP were high in Southeast part and low in Northwest part. From 2000 to 2015, the NPP, GPP and NPP/GPP of Northeast forest showed a fluctuating increase, suggesting the carbon sequestration capacity was gradually enhanced. However, the trends and rates of NPP, GPP and NPP/GPP showed spatial variation. NPP, GPP and NPP/GPP increased significantly in the southern part of the Daxing'anling while decreased significantly in the northern part of the Daxing'anling, and showed a weak increasing trend in the rest of Northeast forest. The increase of annual precipitation was the main factor driving the fluctuating increase of NPP, GPP and NPP/GPP in Northeast forest.
中国东北森林生态系统是重要的碳汇功能区,也是对环境变化响应的敏感区,分析其植被生产力和碳素利用效率的变化特征及其对气候变化的响应对于区域碳收支的准确评估和预测具有重要意义.本研究利用MODIS的长期监测数据,结合植被类型分布数据,对中国东北森林生态系统2000—2015年生产力(净初级生产力NPP、总初级生产力GPP)和碳素利用率(NPP/GPP)时空变化特征进行分析.结果表明: 研究期间,东北森林生态系统平均NPP和GPP分别为346.4和773 g C·m-2·a-1,平均NPP/GPP为0.45.不同森林类型的NPP和GPP依次为针阔混交林>落叶阔叶林>针叶林,NPP/GPP在不同森林类型间无显著差异.NPP和GPP呈现出东南高、西北低的空间分布特点.2000—2015年间,东北森林生态系统NPP、GPP和NPP/GPP呈波动增加趋势,固碳能力逐步增强.NPP、GPP和NPP/GPP的变化趋势和变化速率表现出空间差异性,在大兴安岭南部地区显著增加,在大兴安岭北部地区显著下降,其余区域呈微弱增加趋势.与气候因子的相关性分析表明,年降水量的增加是驱动东北森林生态系统NPP、GPP和NPP/GPP波动增加的主要因素.
Keywords: carbon use efficiency (NPP/GPP); gross primary productivity (GPP); net primary productivity (NPP); northeast forest.