净生态系统生产力(NEP)是估算植被生态系统碳源／汇的重要指标,开展区域NEP时空变化特征分析,对科学评估植被生态系统固碳能力及其气候变化应对措施具有重要意义。研究基于土壤呼吸模型和TEC模型,利用2000-2020年气象数据和遥感数据,采用线性趋势分析、Hurst指数和相关分析等统计方法,对华北地区固碳能力时空变化特征、影响因素及其未来变化趋势进行分析。结果表明:2000-2020年,华北地区年均NEP为228.8 gC/m2,在空间分布上呈现从西北向东南逐步递增的趋势,总体上表现为净固碳。从变化趋势来看,华北地区生态系统的固碳能力总体呈增加趋势,分布面积占比达到88.8%,达到显著增加趋势的面积比例为54.5%(P<0.05),其中河北北部、北京北部、山西西北部、山东西部等地NEP每年每平方米增加9.0 gC以上。华北大部地区NEP年际波动较小,有79.6%的区域多处于较高稳定、高稳定的等级。从变化趋势来看,华北地区有84.9%区域NEP具有强持续性,且NEP未来仍将持续增加的区域面积占比达到51.4%。华北地区NEP的空间分布和年际变化主要受降水的影响,达到显著相关的区域面积占总面积的44.7%,但与气温、日照呈弱正相关,而且不同区域相关性差异明显。其中降水影响空间格局差异极为明显,华北中北部NEP与降水呈显著正相关,南部呈负相关。
Net ecosystem productivity (NEP) is an important index for estimating carbon source/sink of regional vegetation system. Analyzing the distribution characteristics and changing trend of net ecosystem productivity spatially is of great significance to scientifically assess carbon sequestration capacity of ecosystems and formulate policies and measures to cope with climate change. Using the soil respiration model and terrestrial ecosystem carbon flux model (TEC model), combined with MODIS and meteorological data, this paper estimated the NEP in North China from 2000 to 2020. And its spatial distribution characteristics and changing trend were analyzed, using methods of linear regression, the Hurst index, coefficient of variation and other methods. Results showed that: from 2000 to 2020, the annual average NEP in North China was about 228.8 gC/m2. In spatial distribution, the NEP showed an increasing trend from northwest to southeast, representing carbon sink as a whole. From spatial distribution of change trend, the carbon sequestration capacity of North China ecosystems was increasing, especially in the north of Hebei, the north of Beijing, the northwestern Shanxi, the western Shandong with increase of NEP over 9.0 gC/m2. The area of increasing trend with the NEP accounted for 88.8% of the research area, of which 54.5% showed a significantly increasing trend (P<0.05). As for the coefficient of variation (CV), the NEP status in North China presented slight fluctuations with 79.6%% of the area in higher stability and the highest stability. From the NEP change trend analysis, 84.9% of the area in North China was persistent in the future. The NEP in 51.4% of the regions will continue to increase in the future. The spatial distribution and interannual variation of the NEP values were mainly influenced by the values of precipitation, of which 44.7% showed a positive correlation with precipitation. The changes of NEP were slightly positively associated with temperature and sunshine. The responses of NEP in North China to the meteorological factors were diverse in spatial difference of the North China, especially differences by the influence of precipitation. There is a significantly positive correlation between NEP and precipitation in the northern part of North China, and a negative correlation in the south.