Spatiotemporal Analysis of Vegetation Stress in the Mykhailivskyi and Yelanets Steppes under Climate Aridization (2010-2024)

Climate aridization represents an increasing threat to steppe ecosystems in southern Ukraine, driving soil degradation, biodiversity loss, and reduced vegetation productivity. This study examines the spatiotemporal dynamics of vegetation stress in the Mykhailivskyi and Yelanets Steppes over the period 2010-2024, using the Vegetation Condition Index (VCI) derived from MODIS NDVI data for the growing season (April-October). In the Mykhailivskyi Steppe, the mean VCI was 49.7±14.2%, corresponding to the Moderate category (40-60%). While the ecosystem generally maintained the capacity for recovery, certain years exhibited severe stress: VCI values fell to 20.5% in 2012, 36.8% in 2017, and 35.8% in 2024, reflecting significant drought-induced vegetation degradation. Favourable conditions were observed in 2013 (54.4%), 2016 (65.7%), and notably in 2021 (79.7%), indicating substantial recovery. Overall, an upward trend of approximately +1.2% per year was detected, suggesting gradual stabilization of vegetation cover. The Yelanets Steppe showed comparable dynamics, with a mean VCI of 47.3±14.2%, also classified as Moderate. Severe stress occurred in 2012 (21.4%), 2017 (33.8%), and 2024 (34.6%), whereas favourable years – particularly 2016 (56.2-60.5%) and 2021 (85.5%) – reflected recovery and robust vegetation growth. Seasonal analysis indicated VCI values between 47-62% from April to July, decreasing to 34-39% in August-October, when the ecosystems are most susceptible to climatic stress. A positive trend of +1.0% per year suggests some improvement in moisture conditions, although resilience remains fragile under intensifying climate extremes. These findings underscore the vulnerability of Ukrainian steppe ecosystems to climate aridization and highlight the necessity of continuous monitoring to support biodiversity conservation and sustainable land management strategies.