Influences of Seasonal Soil Moisture and Temperature on Vegetation Phenology in the Qilian Mountains

Abstract

Vegetation phenology is a commonly used indicator of ecosystem responses to climate change and plays a vital role in ecosystem carbon and hydrological cycles. Previous studies have mostly focused on the response of vegetation phenology to temperature and precipitation. Soil moisture plays an important role in maintaining vegetation growth. However, our understanding of the influences of soil moisture dynamics on vegetation phenology is sparse. In this study, using a time series of the normalized difference vegetation index (NDVI) from the moderate resolution imaging spectroradiometer (MODIS) dataset (2001–2020), the start of the growing season (SOS), the end of the growing season (EOS), and the length of the growing season (LOS) in the Qilian Mountains (QLMs) were extracted. The spatiotemporal patterns of vegetation phenology (SOS, EOS, and LOS) were explored. The partial coefficient correlations between the SOS, EOS, and seasonal climatic factors (temperature, precipitation, and soil moisture) were analyzed. The results showed that the variation trends of vegetation phenology were not significant (p > 0.05) from 2001 to 2020, the SOS was advanced by 0.510 d/year, the EOS was delayed by 0.066 d/year, and the LOS was prolonged by 0.580 d/year. The SOS was significantly advanced and the LOS significantly shortened with increasing altitude. The seasonal temperature, precipitation, and soil moisture had spatiotemporal heterogeneous effects on the vegetation phenology. Overall, compared with temperature and soil moisture, precipitation had a weaker influence on the vegetation phenology in the QLMs. For different elevation zones, the temperature and soil moisture influenced the vegetation phenology in most areas of the QLMs, and spring temperature was the key driving factor influencing SOS; the autumn soil moisture and autumn temperature made the largest contributions to the variations in EOS at lower (<3500 m a.s.l.) and higher elevations (>3500 m a.s.l.), respectively. For different vegetation types, the spring temperature was the main factor influencing the SOS for broadleaf forests, needleleaf forests, shrublands, and meadows because of the relative lower soil moisture stress. The autumn soil moisture was the main factor influencing EOS for deserts because of the strong soil moisture stress. Our results demonstrate that the soil moisture strongly influences vegetation phenology, especially at lower elevations and water-limited areas. This study provides a scientific basis for better understanding the response of vegetation phenology to climate change in arid mountainous areas and suggests that the variation in soil moisture should be considered in future studies on the influence of climate warming and environmental effects on the phenology of water-limited areas.

Understanding vegetation phenology responses to easily ignored climate factors in china's mid-high latitudes

“…How different vegetation types react to climatic factors is diverse, involving factors such as vegetation growth characteristics, ecological adaptations, and physiological mechanisms 29 . In various vegetation types, the link between phenology and climatic factors may be jointly influenced by several factors, such as growth strategy, photosynthetic efficiency, and water use efficiency 6 , 8 , 73 . The same vegetation type exhibited different patterns of relationships under different climate factors, suggesting a diversity of strategies for vegetation to adapt to climate change.…”

“…Vegetation phenology, denoting the recurrent seasonal fluctuations in vegetation growth, constitutes a crucial indicator of vegetation development with profound implications for terrestrial carbon balance and ecosystem productivity 1 – 5 . As an exceptionally responsive bio-indicator, vegetation phenology is a particularly important asset to climate change, making it an invaluable tool for monitoring ecological responses to shifting climate conditions 3 , 6 – 8 . Over recent decades, the dynamics of vegetation phenology have garnered global attention, highlighting the intricate interplay between phenology and climatic factors 2 , 9 , 10 .…”

Nonlinear Responses of Vegetation Phenology to Climate Change and Urbanization: A Case Study in Beijing, China

“…However, significant prediction errors still exist in certain years. In addition to climate change and urbanization, vegetation phenology may also be affected by other external factors, such as soil conditions and water resources [69]. These factors were not considered in this study, which could lead to prediction errors and biases.…”

Spatiotemporal Variation in Vegetation and Its Driving Mechanisms in the Southwest Alpine Canyon Area of China

“…Temperature variation directly affects vegetation phenology, physiological metabolism, and distribution patterns [12]. As the temperature rises, vegetation phenology tends to shift to an earlier date, leading to the enhancement of plant photosynthesis and water utilization efficiency, thus stimulating vegetation growth [13,14]. However, when the temperature rises to over a certain threshold, plant photosynthesis is inhibited, while respiration is enhanced, nutrient consumption increases, and vegetation growth is inhibited [15,16].…”