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Abstract

Trees are sessile organisms that relate with constant environmental change through both structural and functional plasticity. Changes in the plasticity result in different growth rates through the life of trees that can be accessed by the study of tree rings. Environmental changes, especially climate, have the potential to modulate tree growth and, consequently, be recorded in the tree rings. The study of the interaction between trees and the environment is relevant in a time of fast changes in the landscape and climate. The aim of this study was to better understand how climate and landscape features modulate the growth of tropical tree species. In the present study, growth is analyzed as a synonym of wood formation. Additionally, it was analyzed under two points of view, the first one is the tree-ring analyzes and second one is the carbon allocation in the process of wood formation. To accomplish that, tree species with wide distribution were sampled, including Hymenaea spp. (Leguminosae) and Podocarpus lambertii (Podocarpaceae) both with distinct tree rings. The populations of Hymenaea spp. were sampled in ten sites across a latitudinal gradient from the Equator line to the Tropic of Capricorn. The population of P. lambertii was sampled in a micro refuge in the northern limit of this species distribution. Results show that both temperature and precipitation influence these species growth and that relation depends on the environment in which trees grow. High temperatures seem to be a key limiting factor for the studied specie growth. Moreover, temperature is also an important factor that controls the heartwood deposition in Hymenaea spp. It is important to note that the heartwood deposition represents a high carbon cost for these trees. Additionally, there is a trade-off between in the carbon allocation between the sapwood as produced by the cambium and the heartwood deposition. Precipitation is also a climate variable that influences these species growth. However, the precipitation influence seems to be more dependent on the environmental features of each population site. For instance, in sites higher water availability, trees' growth is more dependent on the precipitation during the wet season, while in sites with lower water availability, and well-drained soils, trees' growth is more dependent on the precipitation during the transition period between dry and wet seasons. It is important to highlight that forest fragmentation, commonly seem in tropical areas, has the potential to make this climate/growth relations weaker. Overall, an increase in air temperature and a decrease in the precipitation, or a concentration of it in a shorter wet season, will likely have a negative impact on trees growth. However, this effect will depend on the environmental characteristics of each population.