Simulação do aumento da temperatura, baseada em um cenário de mudança climática, sob o comportamento do banco de sementes de uma floresta secundária, na região de Manaus

Abstract

Climate change is presented as a threat to the Amazon forest and its biodiversity. Some climate models predict for the period 2071-2100 (compared with 1961-1990), the greatest warming will occur in the Amazon, with increase in temperature 4-8 °C (scenario - most catastrophic). The growing deforestation of the region contributes to the worsening of the situation because the temperature increase is also caused by the exploitation of primary forests and the consequent increase in the extent of secondary forests, where one of the main means of regeneration after that deforestation is the seed bank ground. In view of this, the objective was to simulate different temperature regimes on germination behavior of seeds stored in the soil of secondary forests in the Manaus region, based on a climatic scenario of global warming. In areas of the Biological Dynamics of Forest Fragments Project (PDBFF) located north of Manaus, were collected soil samples with 3 cm depth in six areas of secondary forests. These samples were homogenized and monitoring of the emergence and seedling development was held in chambers with temperature controlled for four months. The current temperature conditions were simulated as much constant (25 °C) and ac (20: 30 °C) and the temperatures projected by the climate model with increasing temperature of 5 °C and 10 °C, with constant temperature of 30 °C and 35 °C and 25 alternating temperature: 35 °C 30 40 °C, respectively. The alternating temperatures simulated fluctuations between day and night temperatures. As provided for seeds of pioneer species, a greater number of emerged seedlings in alternating temperature than at constant temperatures. The higher density and seedling emergence rate occurred in alternating temperatures under current conditions (20: 30 °C) and 5 °C higher (25 35 °C), however there was a drastic reduction in temperature extremes (30:40 °C). However, even alternating temperatures had higher density have not sufucientes to eliminate the need of light for germination, showing that this seed stock experiemento can be classified as positive photoblastic. The results indicate that plant regeneration by the soil seed bank can significantly decrease with rising temperatures predicted by the models of global changes.