Phenology of woody species in a seasonally dry tropical forest: Relationship between phenology parameters, and variation between functional groups and habitats with contrasting abiotic conditions

Abstract

Phenology is the study of the timing of different life cycle events. It is a crucial component of growth and reproduction for both plants and animals that directly influence their fitness. Phenology in plants is not only constrained by environmental factors like temperature, light and water that limit plant function but are also critically linked to biotic factors like the competition between species, and the availability of pollinators and dispersers. Plants in seasonally dry tropical forest experience a broad range of light and water availability, resulting in a huge diversity in phenology.

In the first part of the study, I looked at the general variation in the timing and other parameters for vegetative and reproductive phases and then examined the relationships between them in the context of seasonality in light and water availability in the study site. I found that the species that are flushing and flowering early in the dry season around the spring equinox had a short, synchronous, high intensity activity with low variation between years than species flushing closer to the rains. It also gave insight into how the variation in activity between species cueing to light versus water gives rise to the overall pattern of activity across time.

In the next part of the study, I examined variation in phenology between some of these functional groups. I explored the continuous nature of leafing behaviour in evergreen and deciduous species. The broad range of species deciduousness and its effect on producing a wide variety of vegetative and reproductive phenology is one of the important findings of this study. These results provide essential support for the insolation-limitation hypothesis. Dioecious species flowered earlier, probably to avoid competition for pollinators. Rarer species in the study site probably compensated for their mating opportunity with increased intensity of flowering.

In the last part of the study, I looked at the variation in phenology at the community level, and the relationship of floral abundance to the abundance of pollinators in three habitats with varying abiotic conditions and species composition. Comparison with unweighted phenology pattern revealed that the local microenvironment might be putting similar constraints on different species that overwhelmed the variation that might arise due to differences size and composition of species in these three habitats. Variation in pollinator abundance suggested that other factors may influence the abundance of pollinators that are independent of flowering.

This was a comprehensive study attempting to understand the variation in phenology between species, not only in timing but also in the other parameters, trying to understand the relationships between these parameters and the variation in phenology between habitats with a different microenvironment. Additionally, I also looked at the biotic interactions with pollinators to understand if the variation in floral resources affects pollinators' abundance in these habitats. The study highlighted the limitations of light and water availability differentially affecting the phenology of species giving rise to a wide range of variation in plant phenology in the study site.