Crescimento radial e propriedades tecnológicas da madeira de Tectona grandis Linn f. frente as variações climáticas e ocorrência de evento El Niño na Amazônia

Abstract

The conditions of the environment where the plants are located affect their growth. During the plant development, resources assimilation allows the plant to invest in growth, reproduction, protection, etc. For some tree species, this information is documented in the growth rings, which represent a relative measure of their annual growth and may infer about the operation of the tree for the next periods. From this information documented in the growth rings it is possible to study the responses/strategies of plants in an environment driven by climate change. Climate change have a direct relationship with the occurrence of extreme weather events, such as El Niño, responsible for increasing temperature and reducing precipitation in various parts of the world, including the Amazon region. Thus, this research aimed to evaluate the effect of climate and the occurrence of El Niño event (2015/2016) on the growth and technological properties of the wood of Tectona grandis Linn f.. We used 60 young trees, aged 12 years, from a plantation located in the southeast region of the state of Pará. The trees were sampled by destructive technique, removing discs at different heights of the stem (base, 1.0, 4.1, 7.2 and 10.3 meters). The discs from the base were used to measure the tree-ring width and to evaluate the wood anatomy. Also, the apparent density per ring, was analyzed using the discs from the base and other heights. Allied to the study of growth rings, remote sensing tools were used to contribute to the understanding of tree responses to climate. We used images from the MODIS sensor to obtain the Normalized Difference Vegetation Index (NDVI) and Gross Primary Productivity (GPP) and from landsat-8 satellite to obtain the CO2 flux. The NDVI was used to extract phenological metrics of Start, Peak, End and Length of the growing season, considering the amplitude of its values, for each growth period, to define each of these metrics. To assess the influence of the El Niño event, we considered the pre-El Niño (2012 and 2013), El Niño (2014 and 2015) and post-El Niño (2016 and 2017) periods. Both GPP and CO2 flux were used to better understand the tree's responses regarding biomass accumulation during the El Niño event. The study showed that radial growth, length of growth season, size of vessel elements and wood density were positively correlated with precipitation and negatively with temperature, especially in the initial months of growth season. The El Niño event negatively affected the radial growth, the vessel element size and biomass accumulation. In addition, it was observed that the length of the previous growth season negatively affected the current radial growth. Thus, our study demonstrated the acclimatization of the species to the climate and that, in addition to directly affecting productivity, the climate can also affect the growth of the next season.