Spatiotemporal Evolution of NPP in Sandy Land of China's Seasonal Freezing-Thawing Typical Region

Introduction

In the global ecosystem, vegetation has important indication function in the conservation of soil erosion, regulation of the atmosphere, maintenance of climate, and stability of the entire ecosystem (Richards et al., 2022; Song et al., 2021). Net primary productivity (NPP) can directly represent the apparent changes of ecological environment and ecosystem production capacity, and can be reflected in the process of environmental climate change in geophysics and biogeochemistry (Becknell et al., 2021; Zhou et al., 2022). NPP is important index functions to study various terrestrial ecological processes (Chen et al., 2021). Accurate monitoring of regional NPP has important practical application value for the assessment of vegetation resource changes, exploration of vegetation production potential, and rational utilization of resources (Zhang et al., 2020). It is the important core content of research on contemporary earth material circulation science to estimate regional ecosystem vegetation NPP, quantitatively study its spatiotemporal change characteristics, and analyze its relationship with climate change (Jin et al., 2020). Therefore, the measurement and evaluation of NPP on a global scale or in a specific region has attracted much attention from researchers (Wei et al., 2022). Remote sensing model estimation is an effective method to obtain NPP on a large scale, quickly and accurately (Ge et al., 2022). During the years 1965-1974, scholars from various countries established the CASA, Miami, Thornthwaite, Chikugo, and other models by combining measured data with climate and environmental factors, and conducted a large number of assessments and tests on NPP (Liu et al., 2022). Among the many regional terrestrial NPP estimation models, the CASA model is simple and practical, and is one of the most potential research methods (Zhang et al., 2021).

Freezing-thawing erosion area refers to an area characterized by strong freezing-thawing action and corresponding landform of freezing-thawing erosion (Tao et al., 2021). The sands in China’s seasonal freezing-thawing typical region are located at the northeast sea-land transition zone of the Eurasian continental mid-latitude giant sand belt and the eastern edge of China’s sandy desertification land, and the regional climate and human activities have regional characteristics (Gao et al., 2021). Researchers in China have conducted much work on freeze-thaw area vegetation NPP (Wang et al., 2021). However, most of the research scholars have studied specific study areas, short time series NPP, and its influencing factors, and relatively few studies have been conducted on the spatial distribution of long time series NPP and significant and potential factors affecting NPP changes in the sandy areas of the freezing-thawing erosion area of China. Therefore, in this paper, the authors chose the sand in China’s seasonal freezing-thawing typical region as their research object. They used AVHRR GIMMS, TERRA/AQUA MODIS NDVI data, and the more time and space scales to calculate the sand vegetation NPP dynamic change trend between whole and parts, combined them with meteorological data such as temperature, precipitation, wind speed, and evaporation, and discussed the sand vegetation NPP dynamic evolution and drive. To clarify the change process and driving force of NPP in spatiotemporal evolution of NPP in sandy land of China’s seasonal freezing-thawing typical region, the paper provides basic data for the further implementation of ecological restoration project and ecological civilization construction.