Analysis of Remote Spectral Indices in the Study of Successional Changes of Tundra Vegetation in Postagrogenic Biogeocenoses

A comparative analysis of remote spectral indices has been carried out during the study of changes in the vegetation cover in the postagrogenic biogeocenoses of the Bolshezemelskaya tundra. Successional changes in the species composition of vegetation have been considered to estimate the dynamics of the spectral indices in the meadow biocenoses throughout the agricultural and postagrogenic periods. The spectral characteristics and species composition of vegetation in the surrounding undisturbed biocenoses were used as background indicators. Compared to the surrounding background sites, meadow biogeocenoses used for agriculture had relatively high indices, characterizing the moisture and photosynthetic activity of plant phytomass (NDVI, LWCI, NDMI, and channel B5). Changes in the amount of dead biomass were estimated using the PSRI index, the values of which were minimal during the period of agricultural use of the meadows with regular haying. During self-recovery succession in postagrogenic biogeocenoses, the values of the spectral indices gradually reach the level characteristic of the surrounding background sites. During the postagrogenic period, the LWCI, NDMI, and NDVI values gradually decrease and the values of PSRI and spectral channel B3 increase in meadow biogeocenoses. During the postagrogenic period, sown grass herbage thins out in meadow biogeocenoses, a shrub layer is formed, and species that penetrate from the surrounding communities become dominant and subdominant. The self-recovery of tundra vegetation in postagrogenic biogeocenoses was activated during the period of current climate warming. The effect of climate on the spectral indices was assessed based on the statistical relationships between the values of the climate characteristics and spectral indices in postagrogenic and background biogeocenoses.