Insights into spatiotemporal dynamics and driving mechanisms of vegetation net primary productivity in African terrestrial ecosystems

Abstract

Net Primary Productivity (NPP) is a critical measure of ecosystem vitality. This paper examines the spatiotemporal variation in NPP across Africa during 1981–2018 using Theil-Sen slope estimation and wavelet analysis. Sustainable change characteristics in different regions are analyzed using the Hurst exponent, and the influence of driving factors on African NPP are quantified through a structural equation model (SEM). The analysis revealed that: (1) The annual variation curve of African NPP demonstrated a fluctuating upward trajectory (p = 0.001) throughout the study period. Wavelet analysis revealed a cyclical pattern with a primary period of about 20 years, characterized by two upward and downward transitions during 1981–2018. (2) Spatial analysis indicates the distribution of NPP across Africa is centered around the equator and gradually decreases towards higher latitudes, in which the NPP of tropical rainforest and its adjacent areas increases significantly, covering 40.2 % of Africa’s area. However, Hurst exponent analysis reveals that NPP in Africa generally exhibits anti-sustainability changes, with 52.8 % of the total area potentially shifting from growth to decline in the future. (3) SEM analysis shows that NPP in Africa is mainly regulated by natural factors, particularly cumulative precipitation and temperature extremes, which exhibit the highest impact coefficient of 0.89. While topographic factors also have a substantial overall effect, their impact is primarily indirect through climate, with minimal direct influence. These findings offer a scientific foundation and policy support for sustainable development of environmental and socio-economic systems in Africa.