VCI-Based Analysis on Spatiotemporal Variations of Spring Drought in China

Abstract

The analysis of spatiotemporal variations in drought is important for environmental monitoring and agricultural production. In this study, the spring vegetative drought conditions in China were analyzed by using the vegetation condition index (VCI) as an indicator to reveal the drought characteristics in China from 1981–2015. The results suggest that spring vegetative drought (especially moderate drought) occurs frequently in China, and drought conditions have obvious geographical differences and are highly affected by monsoons. The frequency of spring vegetative drought is relatively high in the southern and northern regions, which are greatly affected by monsoons, and is relatively low in the northwestern and Qinghai-Tibet regions, which are less affected by monsoons. During 1981–2015, the spring VCI in China showed an overall upward trend. In addition, the trend was not a single change but a wave-like increasing trend that can be divided into four stages: (1) a stage of slow growth from 1981–1990, (2) a stage of intense fluctuations from 1991–2000, (3) a stage of steady growth from 2001–2010, and (4) a stage of slow descent after 2010. The Mann–Kendall test confirmed that the spring VCI in China was increasing, and the changes in the southern, northwestern, and Qinghai-Tibet regions reached significant levels. The time point of mutation in the southern region was 2000, and that in the northwestern and Qinghai-Tibet regions was 1992. Wavelet time series analysis showed that spring vegetation drought in China has a short-period oscillation of 5–7 years and a long-period oscillation of approximately 23–28 years. The northwestern and Qinghai-Tibet regions, which are less affected by the monsoons, are dominated by long-period oscillations, while the southern and northern regions, which are more affected by the monsoons, are dominated by short-period oscillations.

Drought Assessment on Vegetation in the Loess Plateau Using a Phenology-Based Vegetation Condition Index

“…Different from the EVI, which directly measures vegetation growth state, the VCI reflects how many differences there are between vegetation status and background value in a given area and can identify drought conditions based on local climate and natural background conditions. It has the potential to mitigate the effects of geographical, climatic and soil factors [17,55]. Therefore, VCI is frequently used to diagnose drought and quantify its onset, severity, duration, and effect on vegetation [56].…”

“…This might be because the SPI/SPEI only measures the meteorological drought, but the VCI/WVCI reflects the comprehensive impacts of meteorological drought on vegetation, including precipitation, temperature, evaporation, vegetation type, and so on. The PDSI is similar to the VCI in that it takes temperature, humidity, evaporation and recharge rate into account [55]. As a result, VCI/WVCI can more accurately reflect the real impacts of drought on vegetation than SPI/SPEI.…”

Spatio-temporal Fluctuation of Temperature Using Specific Climate Indices in South Xinjiang, China

“…The yearly precipitation is less than 158 millimeters. Hotian and Aksu are main rivers in the region (Liang et al, 2021).…”

Vegetation Dynamics in Response to Climate Change and Human Activities in a Typical Alpine Region in the Tibetan Plateau

“…However, other factors also influence vegetation growth [10,38,78,79], such as solar radiation or sunlight hours, soil moisture, etc. For example, previous studies [80,81] have reported that drought-induced soil water deficit is often a…”

“…However, other factors also influence vegetation growth [10,38,78,79], such as solar radiation or sunlight hours, soil moisture, etc. For example, previous studies [80,81] have reported that drought-induced soil water deficit is often a main factor affecting vegetation growth. The influence of other factors on vegetation change should be considered in future studies.…”