Relação do clima com a alocação de carbono estrutural e não estrutural em espécies arbóreas de florestas tropicais
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Data
2019-09-13
Autores
Macieira, Bernardo Pretti Becacici
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Universidade Federal do Espírito Santo
Resumo
Tropical forests have a crucial role of the global carbon and climate cycle, cover 10 % of the surface of the Earth and store 25 % of global terrestrial carbon pool. Structural carbon pool (SC) of tree species that make up tropical forests may account 42 – 61 % dry biomass, while non-structural carbon pool (NSC) range for 25 – 35 %. Therefore, it is important to understand the dynamics of SC (cellulose, hemicelluloses and lignin) and NSC (soluble sugars and starch) allocation in tropical tree species, specifically in the face of climate variations, as well as the relationship of water and carbon in a systemic view. The aim of the present study was to evaluate how short-term climate variations modulate the allocation dynamics of SC and NCS in pioneer (Senna multijuga) and non-pioneer (Hymenaea aurea) tropical trees of Atlantic forest (Chapter 1). Another aim of this study was to provide a systemic view of balance between carbon allocation and hydraulics in different populations of tree species Neotropical Hymenaea courbaril distributed in a microclimate and continentalization gradient (Chapter 2). Our results showed that the leaf and wood SC and NSC pools of S. multijuga and H. aurea were influenced by climate variations with trends of higher values in winter. In this season of lower temperature and precipitation, we observed higher levels of soluble sugars (glucose, fructose and sucrose), hemicelluloses and their galactose and glucose monomers in S. multijuga. In this same season, H. aurea showed higher levels of leaf and wood starch and leaf hemicelluloses, including its arabinose monomer. The only carbohydrate that increased in summer was leaf cellulose in H. aurea. Generally, pioneer tree species showed higher levels of NSC in both source and sink organs, while the non-pioneer tree species exhibited higher levels of SC. Systemic view of H. courbaril populations revealed that changes leaf physiology is not necessarily associated with changes in volumetric growth rate, but it may be associated with changes in wood density. It indicates that trees are likely to invest in the addition of SC in a similar volume of wood. Another interesting result shows that trees precisely finely tune the concentrations of some cell-wall monosaccharides, more specifically xylose and mannose. These changes in cellwall composition are also associated with changes in the allocation of NSC likely related to the resilience of trees. We concluded that short-term climate variations influenced the SC and NSC contents and composition of pioneer and non-pioneer tree species increasing the size of these carbon pools in winter. Systemic view of the balance between carbon allocation and tree hydraulics has indicated that changes in leaf-level physiology, including assimilation and stomatal conductance, is a central feature in the coordination between carbon allocation and water transport in trees with important implications for the resilience of trees to climate change.
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Açúcares solúveis , Amido , Celulose , Floresta Atlântica , Hemiceluloses , Monossacarídeos de parede celular , Atlantic forest , Cellulose , Cell-wall monosaccharides , Hemicelluloses , Soluble sugars , Starch