Ecological Indicators (Feb 2024)
Holistic evolution of ecosystem in Heihe River Basin from the perspective of eigen microstates
Abstract
The impact of environmental change on vegetation dynamics plays a key role in ecosystem evolution, with vegetation demonstrating heightened sensitivity to both climate fluctuations and human activities. However, existing studies have not fully unveiled the emergence of vegetation evolution patterns within the holistic complex systems framework. Based on long-term observational data of the normalized differential vegetation index (NDVI) and meteorological reanalysis data, this study used the mean synthesis and trend analysis methods to explore the spatial distribution and temporal variation of NDVI in the Heihe River Basin (HRB). The results show that a continuous NDVI increase in the HRB from 1982 to 2015, and the growth rate post-2000 being 1.66 times higher than pre-2000, with distinct seasonal periodic fluctuations. Spatially, vegetation thrives predominantly in the upstream and downstream riparian zones of the HRB, displaying significant spatial heterogeneity, and it shows an obvious increasing trend in the middle and lower reaches, especially after 2000. We built a theoretical method using eigen microstates to quantify the dynamic changes in ecosystem vegetation. The first two microstates can account for 64% of the NDVI variations, among which the first microstate captures the overall uptrend and seasonal periodicity of NDVI, while the second microstate highlights the key contributions of soil moisture to vegetation growth. In HRB, soil moisture emerges as the most influential factor for vegetation improvement, surpassing other meteorological variables. Meanwhile, there's a one-month lag in vegetation response to soil moisture, and deeper soil moisture exerts a more pronounced effect on vegetation coverage. This study not only validates the effective applicability of eigen microstates for identifying and attributing ecosystem changes but also provides a new perspective for comprehending the impact of soil moisture on vegetation dynamics.
