Remote sensing analysis of forest vegetation changes due to climate and anthropogenic impacts

摘要

Forest vegetation interaction with climate and anthropogenic stressors is done through a series of complex feedbacks, which are not very well understood. The patterns of forest vegetation are highly determined by temperature, precipitation, solar irradiance, soil conditions and CO_2 concentration. Vegetation impacts climate directly through moisture, energy, and momentum exchanges with the atmosphere and indirectly through biogeochemical processes that alter atmospheric CO_2 concentration. Changes inforest vegetation land use/cover alter the surface albedo and radiation fluxes, leading to a local temperature change and eventually a vegetation response. This albedo (energy) feedback is particularly important when forests mask snow cover. Forest vegetation-climate feedback regimes are designated based on the temporal correlations between the vegetation and and the surface temperature and precipitation. The different feedback regimes are linked to the relative importance of vegetation and soil moisture in determining land-atmosphere interactions. The spatio-temporal dynamics are assessed in terms of the NDVI-surface temperature correlations. Observed vegetation feedbacks on temperature and precipitation are assessed based on Landsat TM, ETM, MODIS and IKONOS satellite data across some forested areas placed in North/Eastern part of Bucharest town as well as in Prahova Valley, Romania for 1989 -2007 period.