Spatiotemporal changes of forest line and canopy cover between 1945-2019 at selected Greek mountains

摘要

The changes observed in forest line, have recently drawn much interest, in part because forest line altitude may be used as an indicator of environmental changes. Forest line ecotone located in the zone between closed forest and to treeless herbaceous vegetation, are transitional areas are widely used as indicators for the observation of landscape response to climate change. The objective of this study was to evaluate the changes in time of the forest line at six mountains in mainland Greece from 1945 to2019. Aerial, remote-sensing data acquired in 1945 and 2007 were processed for information extraction through a visual interpretation approach. Subsequently, the 2007 forest line and canopy cover maps served as reference for developing a modelling procedure based on freely satellite data and extrapolate the forest line predictions over 2019. Spectral and texture predictor variables were extracted from Landsat 5 imagery captured in summer 2007 and used as input to Random Forest models. All models for the various scenes resulted a coefficient of determination of more than 0.6 for tree canopy cover density estimation. The developed RF models for tree canopy cover estimation were applied to Landsat-8 surface reflectance scenes covering the respective geographical extent. Finally, the forest line and tree canopy cover maps, were overlaid within a GIS environment and changes were detected. The change detection procedure revealed both an upslope shift of the forest line as well as an increase in the tree canopy cover in these areas. From these changes, significant implications for ecosystem functioning and ecosystem services provision are likely to occur.