Abstract:

Vegetation dynamics serve as a critical indicator and regulator of global climate change, particularly in arid and semi-arid ecosystems where ecological fragility exacerbates environmental challenges. The desertification prevention and control zone in central Ningxia's desert grasslands is therefore a vital region for understanding vegetation-climate feedback mechanisms; as the largest natural pasture in Ningxia, this also holds great significance for vegetation change research. However, the spatiotemporal evolution characteristics of the normalized difference vegetation index (NDVI) under a long-term time series and its response relationships with climate in this region require further investigation. Based on NDVI, temperature, and precipitation data from 2000 to 2022, the spatiotemporal distribution and variation characteristics, future trends, and dynamic stability of vegetation NDVI in the study area are analyzed using models such as Sen+Mann-Kendall trend analysis, Hurst index, coefficient of variation, and partial correlation analysis. In addition, the relationship between NDVI and temperature and precipitation is discussed. The results showed that: (1) From 2000 to 2022, the annual average NDVI value of vegetation in the study area was relatively low and generally followed a fluctuating upward trend (P<0.01), with a spatial distribution that was “low in the east and west, and high in the middle”. (2) Areas with significant improvement in vegetation interannual variation accounted for 39.30% of the study area (P<0.05), whereas areas with significant vegetation degradation only accounted for 1.75% of the study area (P<0.05). The overall vegetation has shown signs of recovery over the past 23 years. (3) In the study area, 70.12% of the NDVI in the study area had a Hurst value less than 0.5 and 29.88% of the NDVI had a Hurst value greater than 0.5. The reverse characteristics of NDVI future changes are stronger than the same-directional characteristics; 32.64% of the areas are likely to improve in the future whereas 57.64% may experience degradation. The overall trend in vegetation development may be toward degradation, with the main focus on sustained improvement against weakness. (4) Over the past 23 years, the spatial fluctuations in vegetation NDVI have significantly differed, and this generally occurred in a relatively high wave and high fluctuation stage. Vegetation NDVI exhibits both positive and negative correlations with temperature but is positively correlated with precipitation, and vegetation growth is more affected by precipitation factors. The research results provide basic data and a scientific reference for vegetation protection and ecological security in the desertification prevention and control zone in the desert grasslands of central Ningxia.

Key words: vegetation NDVI, spatio-temporal evolution characteristics, temperature and precipitation, the desert grasslands, desertification prevention and control zone, central Ningxia