Abstract:

Understanding vegetation dynamics and their response to climate change is essential to improve the carbon sequestration capacity of terrestrial ecosystems in the context of global change. As an important ecological barrier in north China, Inner Mongolia is one of the provinces with the most diverse climate and ecosystem. While net ecosystem productivity (NEP) is strongly associated with climate change, it is unclear whether and how such responses exist in ecologically fragile areas, such as Inner Mongolia, which contains multiple ecological transition zones and vegetation types. In this study, the NEP of vegetation in Inner Mongolia from 2001 to 2020 was estimated by using the net primary productivity and soil respiration models based on remote sensing vegetation index data, land cover data, and meteorological observation data. The temporal and spatial changes of NEP for different vegetation types and their responses to three typical climatic factors including precipitation, temperature, and solar radiation were studied. The results showed that (1) the vegetation NEP in Inner Mongolia gradually decreased from northeast to southwest, and the average NEP was C 61.2 g·m^-2. The average annual NEP of the forest, grassland, and cultivated land was C 270 g·m^-2, 54.7 g·m^-2, and 140 g·m^-2, respectively. (2) From 2001 to 2020, the terrestrial ecosystem carbon sink in Inner Mongolia showed an upward trend, but there were some fluctuations, among which the NEP of forest and grassland showed an upward trend, while the NEP of cropland showed a downward trend. Forest had the largest mean NEP, followed by cropland and grassland. (3) There were significant differences in the response of NEP to climatic factors for different vegetation types, with the NEP of cropland was mainly affected by solar radiation, the NEP of grassland was controlled by precipitation and solar radiation, and the NEP of forest was under the influence of all three climatic factors. This study is of great importance for evaluating the carbon balance of the terrestrial ecosystem in Inner Mongolia, and also for evaluating the carbon sequestration capacity of the ecosystem and studying its carbon cycle mechanism.

Key words: NEP, CASA model, carbon source/sink, climate change

摘要：

掌握植被动态及其对气候变化的响应，对于提升全球变化背景下陆地生态系统的固碳能力至关重要。内蒙古作为中国北方的重要生态屏障，是气候和生态系统最为多样化的省份之一。虽然已有研究表明植被碳源/碳汇与气候变化密切相关，但这种响应在生态脆弱且包含多种生态过渡带与植被类型的内蒙古，是否存在及如何响应尚不清楚。以净生态系统生产力（NEP）为固碳评估指标，基于遥感植被指数数据、土地覆被数据和气象观测数据，采用净初级生产力和土壤呼吸模型估算了2001-2020年内蒙古植被碳源/碳汇，并通过实测数据验证，重点研究了不同植被类型NEP的时空变化及其对降水、温度和太阳辐射等3种典型气候因子的响应。结果表明，（1）内蒙古植被碳源/碳汇有明显的时空异质性，植被NEP由东北向西南逐渐降低，平均NEP为C 61.2 g·m^-2；不同植被类型的NEP有显著差异，森林、草地和耕地的年均NEP分别为C 270 g·m^-2、54.7 g·m^-2、140 g·m^-2。（2）2001-2020年，内蒙古陆地生态系统碳汇呈上升趋势，但存在一定波动，其中森林和草地NEP呈上升趋势，而耕地NEP呈下降趋势。不同植被类型按照其NEP均值由大到小排序依次为森林、耕地、草地。（3）不同植被类型NEP对气候因子的响应存在显著差异，耕地NEP主要受太阳辐射的影响，草地NEP受降水和太阳辐射的共同控制，森林NEP受3种气候因子的共同影响。该研究对于评估内蒙古陆地生态系统碳平衡，以及对评价生态系统的固碳能力和研究其碳循环机制具有重要的意义。

关键词: 净生态系统生产力, CASA模型, 碳源/碳汇, 气候变化