Resposta de palmeiras a alterações na paisagem por corte e queima e incêndios florestais na Amazônia Oriental

Abstract

Tropical forests play a crucial role in climate control, in addition to providing other ecosystem services of local relevance, such as the supply of forest products to traditional populations. However, these forests have faced increasing levels of degradation due to human activities, including accidental forest fires. In this context, some palm species, especially those of the genus Attalea, proliferate in disturbed habitats, while others are negatively affected by the creation of anthropic landscapes, which should affect the dynamics of regeneration and, perhaps, the flammability of the forest, in this context, this dissertation examines the response of palm trees to the formation of a forest mosaic and the incidence of wildfires in a landscape of the Tapajós-Arapiuns Resex, eastern Amazon. Palm trees were inventoried in four habitats of forest mosaic; mature forest, burnt forest, secondary forests (regenerating forest) and active fields produced by slash-and-burn agriculture, totaling 61 plots of 500 m2 . To examine the contribution of curuá (Attalea spectabilis), the most abundant palm tree in the landscape) to forest flammability, leaf litter from the leaves of this palm tree and leaf litter from the forest floor without curuá material (control) were characterized in relation to four attributes: 1) flame time; 2) ember time and 3) flame height. Other attributes were analyzed, such as dry mass content, moisture content, volatile materials content, ash content and fixed carbon content, in order to understand the flammability pattern of curuá. Ten species of palm trees were identified in the four habitats, both heliophilous palms (pioneers) and shade-tolerant species typical of the forest understory. There was great variation in terms of richness and abundance of palm trees within and between each habitat; on average two species per habitat, but with no difference between habitats. Several species did not respond to the creation of disturbed habitats, but the two Attalea species were more abundant in the field and burned forests compared to the mature forest. It was estimated that the mature forest may contain 21.2 ± 43.4 curuá leaves/ha, while the burned forest may have 259.8 ± 124.6 curuá leaves/ha, the farmland may have 437.8 ± 428 .2 curuá leaves/ha and secondary forests can contain 179.5 ± 225.6 curuá leaves/ha. These numbers provide an indication of the potential of the curuá to add flammable material to the different habitats of the social forest. Curuá leaf litter had a shorter burning time, flame temperature and carbon content, but a higher volatile content. Our results indicate that palm species respond differently to the transformation of mature dryland forest into social forest and to accidental fires. Some species have a neutral response while the pioneer species of Attalea proliferate in disturbed habitats, although there is great variation in the frequency and abundance of these species. Although curuá does not have a higher calorific value than forest leaf litter, this species can add a large amount of material with a low carbon content and high volatile content, which allows rapid ignition and possibly the spread of fire.