近30年来黄河三角洲植被净初级生产力时空特征及主要影响因素

我国拥有丰富的海岸带蓝色碳汇,准确把握海岸带蓝碳生态系统净初级生产力(NPP)状况,辨识不同人为干扰下蓝碳生态系统NPP的时空分布特征具有重要意义。以黄河三角洲为研究区,以近30a(1987年、1995年、2005年、2016—2017年)为时间尺度,通过遥感手段和现场调查,对黄河三角洲NPP时空变化特征及其主要影响因素进行研究。结果显示:(1)近30年来研究区NPP均值和总量呈现先下降又略微增长的特征,2016—2017年度NPP平均值为294.38g C m~(-2)a~(-1),总量为710.05Gg C/a,表现出显著的季节差异。(2)研究区NPP在各行政区、保护区和地表覆盖类型中均表现出了明显的空间分异性;2016—2017年度NPP分区结果显示,不同分区面积由大到小依次为中生产力区(49.5%)、低生产力区(38.3%)和高生产力区(12.1%)。(3)研究区NPP的时空分异性是地表覆盖类型和植被生长状况共同影响的结果,海陆交互作用、开发利用活动和近年来的生态建设是NPP时空变化的主要影响因素。(4)湿地植被和农田是研究区碳汇的主要贡献者,20世纪90年代以来二者NPP均值逐渐上升,在2016—2016年度分别达570.28g C m~(-2)a~(-1)和335.92g C m~(-2)a~(-1);近30年来,湿地植被NPP总量逐渐减少,农田NPP总量则逐渐增加。湿地植被是海岸带蓝碳的典型载体,农田作为位于滨海地区、由湿地植被转化而来、本身具有较高固碳能力和潜力的碳汇类型,可作为海岸带蓝碳的重要补充。

Spatio-temporal characteristics and main influencing factors of vegetation net primary productivity in the Yellow River Delta in recent 30 years

Salt marsh vegetation, mangrove, and sea grass in coastal areas are highly efficient carbon sinks; the carbon sequestrated by these is described as coastal blue carbon and their ecosystems are described as coastal blue carbon ecosystems. The coastline of China is long and the coastal blue carbon ecosystems are widely distributed. With rapid development of economy and consistent increase in CO₂ emission, exploring the potential of coastal blue carbon has become an important way to increase the carbon sink and decrease the pressure of CO₂ emission. It is of great significance to identify the temporal and spatial characteristics of net primary productivity (NPP) in coastal blue carbon ecosystems under various and complex anthropogenic disturbances. The study was conducted in the Yellow River Delta, and the recent 30 years (1987, 1995, 2005 and 2016-2017) was used as the time scale for analysis. The spatio-temporal characteristics and main influencing factors were analyzed using data from remote sensing and field investigations. The results indicated that:The mean value and total amount of NPP decreased first and then increased slightly during the recent 30 years, and the mean values of NPP in the summer of 1987, 1995, 2005, and 2016 were 94.93, 63.90, 64.56, and 69.54g C m^-2 month^-1, respectively. The mean value and total amount of NPP in the year 2016-2017 were 294.38g C m^-2 a^-1 and 710.05 Gg C/a, which showed distinct seasonal differences. Obvious spatial heterogeneity existed in different districts, nature reserves, and land cover types. Comparing the different districts, Lijin County possessed larger temporal fluctuation of NPP than the other two districts. The mean value of NPP inside natural reserves was higher than that outside the natural reserves, which was higher in the experimental zone of the nature reserve than in the buffer and core zones. Further, the mean values of NPP were similar in old and new estuaries in the year 2016-2017. Among the different land cover types, wetland vegetation possessed the highest mean value and total amount of NPP, followed by farmland. The NPP values in other land cover types were low. The results from NPP partitioning for the year 2016-2017 showed that the proportion of area with medium NPP was the most (49.5%), followed by low NPP (38.3%), and high NPP (12.1%). The spatio-temporal characteristics of NPP were determined by land cover types and vegetation growth conditions. The land-sea interaction, exploitation activities, and ecological establishment in recent years were the main influencing factors of the spatio-temporal variations in NPP in the study area. Wetland vegetation and farmland were the main contributors of carbon sink and their mean values of NPP increased steadily since the 1990s, and reached 570.28g C m^-2 a^-1 and 335.92g C m^-2 a ^-1 in the year 2016-2017. In the 30 years, the total amount of NPP continuously decreased in wetland vegetation and increased in farmland. Wetland vegetation is the typical carrier of coastal blue carbon. Meanwhile, farmland, which is located in coastal areas, transformed from wetland vegetation, and possesses high ability and potential for carbon sequestration, can be considered as an important supplement for coastal blue carbon.