Spatiotemporal dynamics of vegetation net ecosystem productivity and its response to drought in Northwest China

ABSTRACT

Net ecosystem productivity (NEP) quantifies magnitude of the terrestrial vegetation carbon sinks. Drought is one of the most important stressors affecting vegetation NEP. At present, the spatiotemporal dynamics of vegetation NEP in drought-prone of Northwest China (NWC) lack discussion under different climatic zones and land cover types, and the response of vegetation NEP to drought remains unclear. Hence, we estimated the vegetation NEP in NWC using ground and remote sensing data and quantified the spatiotemporal differentiation of NEP under different climatic zones and land cover types. The drought fluorescence monitoring index (DFMI) was developed to examine the relationship between vegetation NEP and drought response based on the solar-induced chlorophyll fluorescence (SIF) data. Our results suggested that vegetation carbon sinks increased significantly at 7.09 g C m⁻² yr⁻¹ in NWC during 2000–2019, mainly in northern Shaanxi, eastern and southern Gansu, and southern Ningxia. NEP showed increasing trends under different climatic zones and land cover types, but there were differences in carbon sink capacity. The strongest carbon sink capacity was in humid regions and forests, while the weakest was in arid regions and grasslands. The vegetation carbon sinks showed a non-linear relationship with the drought degree reflecting multiple trend differences, especially in forests and grasslands. The response to drought was faster and more significant in semi-arid and semi-humid transition zones and extreme humid regions when vegetation carbon sinks decreased. DFMI was a good indicator to monitor drought conditions in NWC. NEP and DFMI were an 8–20-month periodic positive correlation and showed a high correlation with high–high and low–low clustering spatially. Drought significantly weakened vegetation carbon sinks in NWC. This study emphasizes the demand to rapidly identify climatic conditions that lead to decrease significantly in vegetation carbon sinks and to formulate adaptation strategies aimed at reducing drought risk under global warming.

KEYWORDS:

• Vegetation NEP
• SIF
• wavelet coherence
• remote sensing
• Northwest China

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data supporting this study’s findings are available on the USGS Land Processes Distributed Active Archive Center (LPDAAC) for MODIS data at http://lpdaac.usgs.gov/. The DEM is freely from NASA’s SRTM data at http://srtm.csi.cgiar.org/, the Landsat images are freely downloaded in the Resource and Environment Science Data Center of the Chinese Academy of Sciences at http://www.resdc.cn/, and the GOSIF data are derived from the NASA Orbiting Carbon Observatory 2 (OCO-2) at https://globalecology.unh.edu/. The meteorological data come from the National Climate Centre of China Meteorological Administration at http://data.cma.cn/.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by the Projects Funded by the Central Government to Guide Local Scientific and Technological Development (22ZY1QA005), the National Natural Scientific Foundation of China (42201459), the National Natural Scientific Foundation of China (42161063), Open Foundation of Key Laboratory of Yellow River Environment of Gansu Province (21YRWEK001), Young Doctoral Fund Project of Higher Education Institutions in Gansu Province (2022QB-058), Research project of Transportation Department of Gansu Province (2021-31), Key R & D programs—Industrial (21YF11GA008), and Jiayuguan City 2021 Science and Technology Plan Projects (No. 21-35).