Estimation of Terrestrial Net Primary Productivity in the Yellow River Basin of China Using Light Use Efficiency Model

Abstract

The net primary productivity (NPP) of vegetation is an essential factor of ecosystem functions, including the biological geochemical carbon cycle, which is often impacted by climate change and human activities. It plays a significant role in comprehending the nature of carbon balance in an ecosystem and demonstrates the global and regional carbon cycle dynamics. The present study used an upgraded CASA model to calculate the NPP in the Yellow River Basin (YRB), China. The model’s simulation ability was improved by changing the model parameters. Further, the CASA model was validated by comparing with MODIS-NPP and in situ observed NPP, wherein the accuracy of the CASA model estimation was found satisfactory to estimate NPP changes in the study area. The simulated results of the improved CASA model showed that the mean annual NPP value of vegetation in the YRB was 283.4 gC m–2 a–1 from 2001 to 2020, with a declining trend in spatial distribution from south to north. In contrast, the NPP appeared as an increasing trend in the YRB temporally from 212 gC m–2 a–1 in 2001 to 342 gC m–2 a–1 in 2020, with a mean annual growth rate of 4.6 gC m–2 a–1. The total NPP in the YRB increased by 40,088.3 GgC between 2001 and 2020, from 226.06 TgC to 266.15 TgC. This rise can be attributed to the increase in forests. The average grassland area has reduced by 4651 km2 during the last two decades, significantly impacting the total NPP of grasslands. Although the increase in NPP in wetlands was minimal, accounting for 815.53 GgC, the highest change percentage of 79.78%, could be observed among the six vegetation types due to the anthropogenic influences and climate change. The conditions favorable for vegetation growth and a sustained environment were enhanced by the increased precipitation and temperature and the reinforced ecological protection by the government.

Has the Establishment of National Key Ecological Function Zones Improved Eco-Environmental Quality?—Evidence from a Quasi-Natural Experiment in 130 Counties in Sichuan Province, China

“…The net primary productivity (NPP) of vegetation, a vital parameter representing terrestrial ecological processes, reflects the productivity and quality of ecosystems [52]. It is frequently employed as a core indicator to characterize EEQ [53].…”

Advances in characterizing and monitoring land cover/use and associated ecosystem changes using remote sensing data

“…NPP has been a research hot spot at the regional level (Wu et al, 2014;Guo et al, 2021). Currently, the CASA model of the light energy utilization model (parametric model) and the MOD17A3HGF remote sensing product calculated using the BIOME-BGC model have been widely used Xiao et al, 2022). Guided by various international conventions on global climate change, the prohibition of deforestation has become a legal provision, and productivity estimates can only be obtained either directly from the field or via remote sensing data.…”

Spatiotemporal dynamics of net primary productivity and its influencing factors in the middle reaches of the Yellow River from 2000 to 2020

“…Ecological measures such as "Grain for Green" and "Three North shelterbelts" have been implemented in the MRYR (Wei et al, 2018), resulting in a significant increase in vegetation coverage, which was directly reflected in the dynamic changes in NPP (Xin et al, 2007;Wang et al, 2009). Previous studies have mainly concentrated on the spatial and temporal distribution of NPP and its correlation with precipitation and temperature in the whole region of the Yellow River Basin (Wang et al, 2022;Xiao et al, 2022). Owing to the Yellow River basin flowing through a wide area, the complicated ecological environment and the obvious regional differences between the upper, middle, and lower reaches, it is difficult to study the NPP of the Yellow River basin as a whole to achieve accurate local implementation.…”