Variações diurnas e sazonais nas trocas de carbono, água e energia em uma floresta primária na Amazônia

Abstract

Anthropic action in natural ecosystems through deforestation, wildfires, improper land use and occupation, industrial activities, and increased burning of fossil fuels are actions directly related to the rise in greenhouse gas concentrations, leading to increased planetary warming, and consequently, an increase in the frequency and intensity of heat extremes, intense precipitation, and an increase in the number of consecutive days without rain, among other extreme events. Tropical forests play a crucial role in regional and global climate, primarily through emissions, gas retention, and evapotranspiration, being extremely important for the global carbon cycle. Using data from a flux tower in the Caxiuanã National Forest, Pará (2005-2008), meteorological data, estimated CO2 exchanges from an Eddy-Covariance system, and remote sensing through satellite vegetation indices (MODIS), the objective was to characterize daily and seasonal changes in CO2 flux in the Caxiuanã forest and examine the relationship between gross primary productivity (GPP) and vegetation indices (EVI and NDVI). The results indicated: i) the behavior of air temperature and evapotranspiration related to solar radiation incidence at the site, which in turn was related to local cloudiness, with higher values during the dry season; ii) sensible and latent heat fluxes were also linked to the local radiation balance; iii) the net CO2 flux from the ecosystem throughout the day was related to the availability of photosynthetically active radiation reaching the leaf canopy; iv) ecosystem respiration peaked at the beginning of the dry season, correlating with temperature increases; v) GPP followed the pattern of water availability and photosynthetically active radiation at the site, with no correlation with NDVI and EVI vegetation indices.