Change in NDVI of forest ecosystems in Northern Caucasus as a function of topography and climate

Abstract

A grid of long-term average July temperature (TJUL) with a grid spacing 500 m was developed to analyze associations between the NDVI vegetation index of mountain forests and climate and topography in the Kuban river basin. The detail of a map obtained based on this grid is substantiated (validation is a special term also used in this paper) by the close association (R2 = 0.978) of temperature on weather stations with topography. It was demonstrated that the long-term average July temperature is significantly determined not only by an altitude (above sea level) but also by the slope insolation (terminology) and valley characteristics. A close nonlinear association with TJUL was detected for the NDVI of mountain forests in this basin. Samples of pine forests close to glaciers reveal close nonlinear associations between the summer NDVI and topography and distance from glaciers. Ecological optima of TJUL were detected for broad-leaved, small-leaved, and pine types of forest in the basin; such an optimum was not established for dark coniferous forests. The average value of NDVI can decrease in predicted NDVI estimations of broad-leaved forests, according to the climatic E GISS scenario, by 2050, since the temperature optimum of forests will move to the area of high-altitude topography, which is characterized by less favorable topographical conditions for the development of forests.