## 4 Discussion
### The Relative Effects of Climate Change and Human Activities on ANPP  
The alteration in ANPP is primarily induced by human activities and climate fluctuations. Numerous preceding studies have utilized ANPP, HNPP, and PNPP to differentiate these two elements' effects on ANPP [18; 48; 49; 61; 62; 86]. Our research findings indicate that a combined influence of climate change and human activities has led to the increase in ANPP in the study area, with their combined effect being greater than the individual impacts of climate change or human activities on the vegetation's ANPP. This increase can be ascribed to the escalating temperatures and heightened precipitation in the region, which create conducive climatic conditions in most areas. These factors boost photosynthesis and carbon storage in vegetation, ultimately contributing to the elevation of ANPP [87; 88]. Additionally, human-driven efforts towards vegetation restoration, including grassland conservation policies and diverse ecological restoration initiatives, have markedly enhanced vegetation coverage and alleviated the detrimental effects of human activities on ANPP [89; 90]. Thus, in most of the areas within the study region where there is an increase, the growth in ANPP is dominantly driven by both climate change and human activities [62]. The increase in ANPP in certain mountainous regions of the study area can be attributed solely to climate change. This positive effect is likely due to two factors: the lack of human activity in these secluded mountainous regions and the favorable conditions created by increased temperatures for vegetation growth. Temperature is a critical factor that limits plant growth. Research has indicated [88; 91] that in areas with an elevation of approximately 1000 m, photosynthesis in vegetation is often hindered at temperatures below 20 \({}^{\circ}\)C, which results in a lower ANPP in many mountainous areas due to the cooler climate. Nevertheless, as per the research presented in Section 3.5 of this study, the study region experienced a general upward trend in annual average temperatures from 2001 to 2018. The gradual increase in temperature promotes vegetation growth [89; 92], especially in mountainous areas, leading to a positive influence of climate change in these regions. Regions where solely human interventions have resulted in a rise in the ANPP were predominantly concentrated in southern Henan Province, northern Hubei Province, northern Anhui Province, central-southern Yunnan Province, and central-northern Guizhou Province. These areas are primarily characterized by farmlands and the karst regions of China. In these regions, the impact of climate change on ANPP is relatively minor compared to human activities. As analyzed in Section 4.1, the areas of southern Henan, northern Hubei, and northern Anhui are abundant in farmlands, where human activities, closely linked to agricultural practices, play a significant role. Factors such as expanded farmland area or enhanced efficiency of land use are largely due to human involvement [67; 68]. In Yunnan and Guizhou Province, located in the Southwest China karst region, ecological protection projects, ecological migration, and initiatives such as converting farmland back to forest or grassland have created favorable conditions for the accumulation of ANPP [93]. Numerous studies have revealed an increase in vegetation cover and a growing trend of ANPP in the Southwest China karst region [89; 93; 94; 95]. As a result, human interventions have resulted in a rise in ANPP in these areas, exerting a more significant effect than that of climate change. In coastal areas where ANPP has declined, human activities have been the primary factor driving the reduction, with their negative impact being more significant than that of climate change, aligning with the findings of previous research [76; 87; 88]. This is likely due to the rapid urbanization in these regions.