2000—2015年青海高原植被碳源/汇时空格局及变化

Abstract

陆地生态系统碳循环能够综合反映全球气候变化及区域响应，是全球及区域气候变化及人类活动影响研究的重要内容。青海高原作为青藏高原的重要组成部分，在全球及区域气候与环境变化中具有极其重要的作用。因此，研究青海高原植被碳源/汇时空变化及气候因子的影响具有重要意义。采用土壤呼吸模型和改进的CASA模型，结合MODIS、气象数据估算了青海高原2000-2015年植被净生态系统生产力（NEP），分析了植被NEP、碳汇的年际时空分布、年际动态变化、多年累积空间分布与植被NEP变异系数，定量分析了降水量、气温对植被NEP的影响。结果表明：1）2000-2015年，青海高原植被年NEP空间分布特点呈东高西低、南高北低，由西北向东南逐步增加趋势，年NEP多年平均值为128.40 gC m^-2a^-1；2）青海高原不同生态区植被NEP与碳汇量空间分异显著，碳汇区约占植被分布区面积的73.11%，其中，祁连山生态区和三江源生态区为主要的碳汇区；3）2000-2015年，青海高原植被碳汇功能逐步增强，年固碳量为-3.2-64.42 TgC，年际变化呈平稳上升；4）受自然与人为因素的协同影响，青海高原年NEP呈现逐步好转的趋势，平均趋势系数为1.52，NEP增加的区域占植被总面积的25.72%；5）青海高原植被NEP变异系数空间分布以较低、中等波动为主，稳定性颇高；6）降水量对植被NEP以促进作用为主，气温以抑制作用为主，气温对青海高原植被NEP的影响占主导地位。;The carbon cycle of terrestrial ecosystem relates to global climate change and its regional response comprehensively. Therefore, it is an important part of climate changes research and the impact of human activities. As an important part of the Qinghai-Tibet Plateau, the Qinghai Plateau plays an important role in the global and regional climate and environmental changes. Therefore, it is of great significance to study the temporal and spatial variation of carbon source/sink of vegetation and the influence of climate factors in Qinghai Plateau. By using the soil respiration model and the improved Carnegie Ames Stanford Approach (CASA) model, combined with MODIS and meteorological data, we estimated the net ecosystem productivity (NEP) of the Qinghai Plateau from 2000 to 2015, analyzed the inter-annual spatial and temporal distribution, the inter-annual dynamics and the multi-year accumulation spatial distribution of vegetation NEP and carbon sink, calculated the coefficient variation of vegetation NEP. We quantitatively discussed the impact of precipitation and temperature on vegetation NEP. The results indicate that 1) during 2000 and 2015, the spatial distribution characteristics of the annual vegetation NEP are high in the east and the south, low in the west and the north, and gradually increase from the northwest to the southeast. The annual average of NEP is 128.40 gC m^-2a^-1. 2) There is a significant spatial distribution of vegetation NEP and the amount of carbon sinks between different ecological regions, the total carbon sink area accounts for about 73.11% of the total vegetation area in Qinghai Plateau, of which the Qilian Mountain Ecological Area and the Sanjiangyuan Ecological Area are the main carbon sink areas.3) From 2000 to 2015, the carbon sink function of vegetation in Qinghai Plateau is gradually enhanced, and the annual carbon sequestration is -3.2—64.42 TgC. And the inter-annual variation of the carbon sequestration increases stably. 4) Influenced by the combination of natural and human factors, the annual NEP of Qinghai Plateau shows a gradually improvement trend, with an average trend coefficient of 1.52, and the area where NEP increases accounted for 25.72% of the total vegetation area. 5) The spatial distribution of NEP variation coefficient in Qinghai Plateau is mainly low and medium fluctuation, and the stability is quite high. 6) The precipitation mainly promotes vegetation NEP accumulation, the temperature inhibits the accumulation of NEP. And the influence of temperature on NEP accumulation is dominant.