Hydrothermal modulation of NDVI in the high-altitude semiarid Andes of Chile (30-34°S)

The impact of future climate change on the native vegetation of subtropical Andes is relatively unknown. The semiarid region of north-central Chile (30-34 degrees S) has experienced a mega-drought over the last decade, with a partial recovery during the 2015 El Nino year. To characterize the vegetation response to climate variability, we analyzed the seasonal precipitation, potential evapotranspiration, temperature extremes, and high-resolution normalized difference vegetation index (NDVI) data at five altitudinal floors above 2500 m. We considered the bi-monthly maximum NDVI in austral summer (NDVIx) and the difference between NDVIx and that of two months prior (NDVId) to reflect the primary productivity throughout the growing season. We observed positive linear correlations between NDVIx and winter precipitation and negative ones with autumn/winter maximum temperatures at lower altitudes (the latter likely led to the negative correlation between NDVIx and potential evapotranspiration). The NDVIx showed clear latitudinal and altitudinal variability, with the southern region exhibiting an opposite NDVIx climate correlation pattern at altitudes greater than 3500 m. The NDVId correlations were more spatially uniform and showed similar patterns to those of NDVIx at lower altitudes. Precipitation declined at a rate of-45%/decade, which contributed to the -1.5%/decade and -5%/decade decline in NDVIx and NDVId, respectively. The positive NDVIx trends (1.5%/decade) above 3500 m in the southern region led to an early snowpack retreat, which was consistent with the temporal increase in autumn maximum temperature of 1.23 degrees C/decade. Our results suggest that ongoing climate change will have a negative impact on the high-altitude ecosystems of the semiarid Andes.

Automated summary

The study showed that the semiarid region of north-central Chile experienced a mega-drought over the last decade. Analysis revealed correlations between NDVI index and precipitation and temperature, indicating a negative impact of climate change on high-altitude ecosystems.