Efeito do fogo induzido na germinação de Astrocaryum jauari (Mart.) em cenários de mudanças climáticas

Abstract

The palm tree Astrocaryum jauari Mart. has adaptations that allow it to survive in flooded Amazonian environments and is found in high abundance in flooded forest areas with a history of deforestation and/or fire. With the objective of elucidating the germinal ecology and the initial establishment of the species, A. jauari diaspores were collected in the terrestrial phase in three areas in the Central Amazon and a fire experiment was carried out. For the experiment, the diaspores were buried in the soil at a depth of 1 cm and covered with litter, then subjected to controlled burning for 4 minutes, a germination was evaluated in a greenhouse and in microcosms that simulated the current climate and four predicted climate scenarios according to the IPCC 2007 report. The experiment was carried out in a bifactorial scheme with factor 1 containing diaspores without exposure to fire (control) and diaspores exposed to fire, with six replications of 25 diaspores in each environment totaling 1,500 diaspores in the experiment. Factor 2 tested the diaspores with and without fire exposure in five climatic scenarios: the greenhouse - subject to the current climatic conditions of Manaus, with shading of 75%, and in the microcosm, the four climatic scenarios predicted by the IPCC 2007 report. These are based on the temperature and CO2 of room 1 - control to which the increases were added automatically in the following proportions: room 2 (1.5 °C; 200 ppm - mild), room 3 (2.5 °C; 400 ppm - intermediate) and room 4 (4.5 °C; 850 ppm - extreme). A germination was monitored every 3 days for 306 days. The fire treatment positively affected germination in all the environments tested. The extreme scenario positively influenced both the fire treatment and the control, with the percentage and speed of germination around 75% and 0.8, respectively. There was no significant difference in the germination percentage in the greenhouse and the control, mild and intermediate scenarios. The median germination time of the diaspores subjected to fire was 50 days and the diaspores not subjected to fire were 250 days. It can be concluded that fire induced the breakage in dormancy in the diaspores. When these were exposed to the extreme scenario, the germination percentage of A. jauari reached about 75%, possibly due to the acceleration of the dormancy breakage under these simulated conditions of high temperature and high CO2 concentration. The high abundance and even monodominance of this species in flooded forests show this species to be a possible indicator of the occurrence of fire-related disturbances in the past.