## 3 Results  
### Spatial and Temporal Characteristics of NEP  
The mean value of the annual vegetation carbon sink in the Taihang Mountains was obtained by using the NEP estimation model on a term-by-term meta-calculation basis, and the mean value of the vegetation carbon sink in the Taihang Mountains from 2000 to 2022 was about 289 gC\(\cdot\)m\({}^{-2}\cdot\)a\({}^{-1}\). As shown in Figure 3, the contribution of vegetation carbon sinks in the Taihang Mountains from 2000 to 2022 is mainly concentrated in the large mountainous areas in the central and western parts of the country, with an area of more than 300 gC\(\cdot\)m\({}^{-2}\cdot\)a\({}^{-1}\) accounting for 75% of the total area, and the mean value of the NEPcan reach a maximum of 658.408 gC\(\cdot\)m\({}^{-2}\)\(\cdot\)a\({}^{-1}\), which is located mainly in the mountainous regions of Xinzhou, Datong, and Shuozhou in Shanxi and in the mountain ranges of Jinzhong, China. Combined with the topographic and geographical characteristics, the region has a high topography, and the vegetation is mainly dominated by woodland grass status. In the western part of the Taihang Mountains, the mean value of vegetation carbon sinks is low, and the average value of NEP can be as low as \(-\)39.7872 gC\(\cdot\)m\({}^{-2}\)\(\cdot\)a\({}^{-1}\), which exists in the form of carbon sources. This is mainly due to the fact that the western Taihang Mountains, including Shijiazhuang, Baoding, and Xingtai, are low-lying and are part of the Hebei plains, where cultivated vegetation, such as farmland and arable land, occupies a major area, and its contribution to carbon sinks is relatively low compared to that of woodland and grassland. Overall, the vegetation carbon sinks in the Taihang Mountains show a spatial pattern of high in the centre-west and low in the northeast, gradually increasing from the northeast to the southwest. Combined with geographic features, regional elevation and vegetation type were found to be important factors in the spatial heterogeneity of the vegetation carbon sink.  
From the time series of NEP in the Taihang Mountains (Figure 4), the mean value of vegetation carbon sinks increased significantly from 222.19 gC\(\cdot\)m\({}^{-2}\)\(\cdot\)a\({}^{-1}\) in 2000 to 357.78 gC\(\cdot\)m\({}^{-2}\)\(\cdot\)a\({}^{-1}\) in 2022. Especially before 2005, the growth trend in NEP was obvious, thanks to important measures such as China's vigorous reforestation programme and the construction of nature reserve projects at the end of the last century. Since then, economic development has been running smoothly, alongside environmental protection. Along with the \"lucid waters and lush mountains are invaluable assets\" concept, \"ecological civilisation construction\", \"Carbon Peaking and Carbon Neutrality Goals\", and other strategies that have been put forward one after another, the carbon sink of the vegetation in the Taihang Mountain area has also reached a new peak. Taken together, during these 23 years, the vegetation carbon sink in the Taihang Mountains as a whole has shown a fluctuating upward trend, and the capacity of vegetation carbon sequestration has continued to rise steadily.  
Figure 3: Spatial distribution of mean values of NEP in the Taihang Mountains, 2000–2022.