Extreme temperatures affect NDVI in Karst ecological fragile area.

Extreme weather events and frequent meteorological disasters pose significant threats to vegetation growth in the context of climate change. However, information regarding the impact of extreme climate events on vegetation in the ecologically fragile Karst area has been lacking. This study aims to fill this knowledge gap by quantifying changes in extreme temperature and the normalized difference vegetation index (NDVI) while exploring the relationship between extreme temperature and NDVI in Guangxi's Karst area, China. Our analysis reveals a pronounced trend toward extreme warming in the study region from 2000 to 2019. Warm days TX90d, TX95d, and TX99d (count of days where daily maximum temperature TX > 90th, 95th, and 99th percentile) significantly (P < 0.05) increased 7.1, 5.5, and 2.0 days per decade. Warm nights TN90d, TN95d, and TN98d (count of nights where daily minimum temperature TN > 90th, 95th, and 98th percentile) significantly (P < 0.05) increased 9.7, 6.8, and 4.2 days per decade, with the increase rate greater than warm days. Annual days for daily maximum temperature higher than 35 °C also increased 3.4 days per decade. The annual NDVI increased 0.04 per decade. We have identified a negative linear relationship between the trends of very cold and very warm days (i.e., very cold days TX01d and hot days TX99d) and NDVI. In contrast, the annual NDVI demonstrates a positive correlation with the annual days for daily maximum temperature higher than 35 °C. The results suggested that climate warming might to some extent benefit the vegetation growth. Nevertheless, it is imperative to enhance vegetation protection efforts, particularly in regions experiencing extreme warm and cold. [ABSTRACT FROM AUTHOR]