Abstract
The timing, duration, magnitude and synchronicity of plant life cycles are fundamental aspects of community dynamics and ecosystem functioning, and information on phenodynamics is essential for accurate vegetation classification and modeling. Here, we recorded the vegetative and reproductive phenodynamics of 479 individuals belonging to 182 tree species monthly over two years in a lowland Atlantic Forest in southeastern Brazil, and assessed the relationship between local climatic conditions and the occurrence and intensity of phenophases. We found a constant but low intensity of occurrence of both leaf fall and leaf flush with respect to canopy cover, resulting in an evergreen cover throughout the year. The timing of the reproductive phenophases was irregular between the two years of observation, and their amplitude was low. In addition, flowering and fruiting phenograms of activity, intensity and intensity corrected by the basal area did not overlap. These results suggest that a combination of phenological records and community-structure parameters allows for the obtainment of more accurate estimates of resource availability over time. We found that differences in growing degree-days (GDD), photoperiod and precipitation over time were related to temporal variation in leaf fall, leaf flush and flowering, with a large consistency in responses across tree species in this lowland Atlantic Forest. Moreover, there was only a weak relationship between climatic conditions and the dynamics of fruit formation and ripening, which were more strongly related to flowering phenodynamics, which is suggestive of indirect effects of climatic conditions on fruiting. Finally, the association we found between the number of days with precipitation and leaf fall dynamics agrees with the view that the greater potential for extreme events may impair plant growth in tropical forests. This reinforces the growing concerns regarding the risk of ecological collapse of tropical forests due to fragmentation and global climate change.
Highlights
The timing, duration, magnitude and synchronicity of plant life cycles are fundamental aspects of community dynamics and ecosystem functioning [1]
The phenograms for activity, Fournier intensity, and intensity corrected by the basal area showed similar overall curves for leaf fall and flush in the community (Figure 2A,B,F,G)
The peaks and troughs of leaf fall did not match exactly with the dry- to wet-season cycle, the events of highest leaf fall occurred in the dry seasons in all years (Figure 2A,F)
Summary
The timing, duration, magnitude and synchronicity of plant life cycles are fundamental aspects of community dynamics and ecosystem functioning [1]. Phenological data are among the most valuable indicators of ecological responses to climate change, as phenology is the natural aspect of simple. Phenological studies constitute the basis for understanding the dynamics of resource availability for populations of many animal species in tropical forests [4], and are important tools for biodiversity monitoring, management and conservation [5,6]. Many conclusions about the phenological patterns and their relationships with climatic conditions in tropical communities are based only on qualitative information (i.e., data on presence/absence of phenophases). Qualitative measures of activity coupled with quantitative data on intensity are fundamental for more accurate definition of plant phenodynamics at the community and population levels [11,12]
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