Assessing the Distribution and Driving Effects of Net Primary Productivity along an Elevation Gradient in Subtropical Regions of China

Abstract

Globally, forest ecosystems, especially subtropical forests, play a central role in biogeochemical cycles and climate regulation, demonstrating their irreplaceable function. The subtropical region of China, characterized by its unique forest ecosystem, complex terrain, climate heterogeneity, diverse vegetation types, and frequent human activities, underscores the importance of the in-depth study of its net primary productivity (NPP). This paper employs the eddy covariance–light use efficiency (EC-LUE) model to quantitatively estimate the gross primary productivity (GPP) of this region from 2001 to 2018, followed by an estimation of the actual net primary productivity (ANPP) using the carbon use efficiency (CUE). The results showed that over these 18 years, the annual average ANPP was 677.17 gC m−2 a−1, exhibiting an overall increasing trend, particularly in mountainous areas, reserves, and the cultivated lands of the northeastern plains, whereas a significant decrease was observed around the urban agglomerations on the southeast coast. Furthermore, the Thornthwaite memorial model was applied to calculate the potential net primary productivity (PNPP), and diverse scenarios were set to quantitatively evaluate the impact of climate change and human activities on the vegetation productivity in the study area. It was found that in areas where the ANPP increased, both human activities and climate change jointly influenced ANPP dynamics; in areas with a decreased ANPP, the impact of human activities was particularly significant. Additionally, the heterogeneous distribution of ANPP across different altitudinal gradients and the driving effects of various climatic factors were analyzed. Finally, a partial correlation analysis was used to examine the relationships between the temperature, precipitation, and ANPP. This study indicated that temperature and precipitation have a substantial impact on the growth and distribution of vegetation in the region, yet the extent of this influence shows considerable variation among different areas. This provides a robust scientific basis for further research and understanding of the carbon dynamics of subtropical forest ecosystems and their role in the global carbon cycle.

The Impact of Climate Change and Human Activities on the Spatial and Temporal Variations of Vegetation NPP in the Hilly-Plain Region of Shandong Province, China

“…Climate change is the internal source of vegetation change, while human activities are the external reason [12,[23][24][25][26][27][28]. Our study elucidates the correlation between the annual average NPP size of varying land use typologies within the SDHP: woodland dominates, followed by farmland, grasslands, shrubberies, and other land categories (Figure 6b).…”

“…Related studies have confirmed that high temperatures have an inhibitory effect on vegetation growth and productivity [16,23,24,26]. Vegetation and productivity in China have been deeply affected by climate change [14,27]. These studies emphasize that climate change, especially precipitation and temperature, are important climate factors affecting vegetation cover, productivity, and spatiotemporal differences [16,22,28].…”

“…The result shows a general trend of increasing precipitation from southeast to northwest in the regional distribution of the positive correlation and significance of precipitation on the SDHP vegetation NPP (Figure 10b,d). This is due to southeast winds controlling the temperate monsoon zone [14,19,23,27]. Therefore, considering the spatial disparities in the response of vegetation NPP to rainfall, it is noteworthy that the JLP's geographical position near the coast results in it being significantly influenced by monsoon weather.…”

Structure and Carbon Capture of a Temperate Mixed Forest across Altitudinal Gradients in Northern Mexico

“…C storage and C emissions are unique to tree species and age, type of soil, altitude, and slope, therefore these parameters vary between tropical, temperate, or boreal forests, as well as between natural and managed forests [5]. C storage variations with altitude are crucial in the context of global warming because of their association with temperature [10,[17][18][19][20].…”