Padrões fenológicos e mortalidade de árvores de terra firme na Amazônia Central

Abstract

The cycles of tree growth, reproduction and death result from complex interactions between factors such as climate, functional characteristics of the species, biological interactions and time. Predictions about how trees respond to climate change have been one of the main subjects in recent ecological studies, as evidence points to rapid climate change in recent decades. Much of this research has been done on phenological components - reproductive and growth cycles, and on tree mortality patterns. However, there are still many uncertainties about the main effects of climate variables on different aspects of phenology and dynamics of rainforest mortality, and consequently how this affects global water and carbon cycles. To identify the phenological patterns of long-lived trees, periodic observations are preferred over short intervals between re-measurements and over the longest possible period of time. Thus, it is possible to identify patterns even if the cycles are rare or quickly, evaluating the long-term trends and possible changes that may occur over time. However, we still do not know what the effect of monitoring time on the characterization and variation of phenological metrics obtained from different monitoring times is. For mortality, the monthly monitoring of species with different functional ecological characteristics allows understanding of how biological and climatic factors increase the risk of death overtime. We used a long time series of monthly observations of Amazonian trees to evaluate mortality and phenology patterns over time, responding to 3 main questions: (i) How climatic variables and functional characteristics affect mortality over time? (ii) How does monitoring time affect the characterization of phenological patterns of tropical trees? (iii) How do climatic variables and functional characteristics affect the occurrence and duration of phenological cycles? Our results show that long-term studies are essential in understanding the effect of important variables on mortality and phenology of tropical trees, contributing to the knowledge about the ecological strategies of these species and on how climatic variables affect reproduction, vegetative patterns and tree death. Our results also indicate the signs of how global climate change affecting the large Amazonian trees, with uncertain consequences for the carbon stock and ecosystem function of Amazonian forests.