Influência da mudança do uso da terra no estoque de biomassa acima do solo em florestas secundárias durante os anos de 2000 e 2014 no Estado do Pará, Brasil.

Abstract

Secondary forests provide important ecosystem services, especially in helping to mitigate climate change. The expressive growth rate causes the intensive removal of atmospheric CO2 and the storage of carbon in the biomass of tree species. This service depends on the conditions of regeneration and development of secondary forests, which are influenced by previous use, the magnitude of the disturbances and the duration of the disturbances. Therefore, it is necessary to understand the formation process of secondary forests in order to identify the potential for mitigating global warming due to the regional contexts of land use and change in land use in the Amazon. In order to analyze the influential factors and the estimates of biomass and carbon in secondary forests, we highlight the methods that combine data from forest inventory and remote sensing, such as images from satellite sensors and point clouds obtained by LiDAR (Light Detection and Ranging), with mathematical and spatial modeling. In this context, the present research aimed to know the spatial distribution and estimate the accumulation of biomass in secondary forests in the state of Pará. The spatial patterns of secondary forests in Pará were evaluated by kernel density algorithms and by hotspot analysis using data provided by the project. TerraClass. In order to map the regeneration of secondary forests, data on land use class were used to attribute the previous use in the years 2000, 2004, 2008, 2010, 2012 and 2014. Through cartographic modeling, the permanence and the emergence of secondary forests in the analyzed chronosequence, making it possible to identify age groups in each year of study and by class of previous use. Biomass estimate data resulting from LiDAR statistical modeling were combined with forest inventories for secondary forests in the municipalities of Paragominas and Santarém provided by Longo et al. (2016), Almeida et al. (2019) and Baccini et al. (2012), as well as biomass data estimated in primary forest from the RainFor project. The results showed that the spatial distribution of secondary forests does not occur randomly in space, suggesting local geopolitical influences. Considering the dynamics of secondary forests in the state's landscape, the positive balance of 16.0 thousand km² between 2012 and 2014 decreased by 2.4% in relation to the period from 2010 to 2012. The decrease in secondary forest areas was influenced by the high-rate deforestation (11,500 km² year-1), almost three times the rate of increase (4,300 km² year-1) between 2012 and 2014. It was found that there was an accumulation of average biomass in secondary forests above of 14 years is 73.57 MgC.ha-1, corresponding on average to 27.48% of the biomass of a mature forest in the same region a for both municipalities, being significant (p <0.001) over time at the ages of secondary forests. There was a significant difference (p <0.001) between biomasses comparing the municipalities of Paragominas and Tapajós when related to the accumulation of biomass in the studied period for the three databases. Secondary forests from mature forests or pasture recover more biomass over time and are age dependent.