陆地生态系统碳收支时空变化及影响因素——以湖南省郴州市为例

Spatio-Temporal Characteristics and Driving Factors of Terrestrial Carbon Uptake:A Case Study of Chenzhou City,Hunan Province

陆地生态系统碳收支不仅是衡量地表生态环境的重要参数,也是全球碳循环的关键变量。以国家低碳试点城市、可持续发展创新示范区——湖南省郴州市为研究区域,耦合多源遥感数据,结合土壤呼吸地统计模型、趋势分析、地理探测器和残差分析等方法,系统开展了2001~2020年植被净生态系统生产力(NEP)时空变化特征分析及影响因素探究。结果表明:(1)在时间上,2001~2020年郴州市总体表现为碳汇,年均固碳总量达5.943×106 T Ca^(-1),NEP均值310.351 g Cm^(-2),平均增长速率2.066 g Cm^(-2)a^(-1)。(2)在空间上,NEP总体呈西高东低、北高南低分布,显著增加(P<0.05)的区域面积占比为40.304%,主要集中在西部。不同植被类型碳汇水平差异表现为:林地(328.100 g Cm^(-2))>草地(318.650 g Cm^(-2))>耕地(257.509 g Cm^(-2))。(3)郴州市生态系统碳收支驱动机制复杂。NEP与气温、日照时数、相对湿度和高程等因子呈正相关,而与降水量和地表净辐射呈负相关,双因子对NEP空间分异性的交互作用明显高于单因子。(4)自然因子是郴州市植被NEP变化的主导因素(95.896%),但在城市边缘区等人类活动剧烈的区域,土地利用/覆被变化平均贡献率达59.761%。研究结果有助于准确把握区域陆地生态系统碳收支时空特征及其内在驱动机制,并为区域生态系统管理与可持续发展提供科学依据。

Terrestrial ecosystem carbon uptake is an important parameter to measure the surface ecology,and also a key variable of global carbon cycle.Chenzhou City of Hunan Province was selected as the study area,which is one of low-carbon city pilots and the Innovation Demonstration Zones for National Sustainable Development.Combined with multi-source data,Geostatistical Model of Soil Respiration(GSMSR),trend analysis,GeoDetector and residual analysis were used to reveal the spatial and temporal variation characteristics and driving factors of Net ecosystem productivity systematically.The results showed that:(1)Temporally,Chenzhou was a carbon pool from 2001 to 2020,with an average carbon sequestration of 5.943×106 T Ca^(-1),mean value of 310.351 g Cm^(-2) and an average rate of increase of 2.066 g Cm^(-2)a^(-1).(2)Spatially,NEP changes was obvious,with higher NEP in the west and north and lower NEP in the east and south.NEP of different land types varied noticeably,among which forest was the highest(328.10 g Cm^(-2)),followed by grassland(318.65 g Cm^(-2))and farmland(257.51 g Cm^(-2)).(3)The driving mechanisms of carbon fluxes in terrestrial ecosystems were diverse.NEP was positively correlated with temperature,sunshine hours,relative humidity and elevation.On the contrary,NEP was negatively correlated with precipitation and net surface radiation.In addition,the effect of two-factors interaction on NEP was obviously higher than that of the single factor.(4)Natural factors dominated the change of NEP,with an average contribution of 95.896%,while the contribution rate of land use was about 4.104%.However,in areas with intense human activities such as urban fringe,the contribution rate of land use increased significantly,with an average rate of 59.761%.The above results can help accurately grasp the spatio-temporal characteristics of the carbon sink effects of regional terrestrial ecosystems and the intrinsic driving mechanisms.Outcomes of this study provide a scientific basis for regional ecosystem management and sustainable development.