Systematic effects of environmental factors and phenology on forest structure: Tracking the ecological processes

Abstract

Numerous studies have demonstrated the significance of climatic and edaphic conditions in regulating the species composition and forest structure. However, there is still a lack of knowledge regarding the ecological processes that are brought about by phenological expression and regeneration. This study postulates that phenology, regeneration, and species dominance are a sequence of intermediary processes through which environmental conditions affect forest structure. In a dry deciduous forest of Similipal Biosphere Reserve (SBR), India, we analysed the relationships between various environmental characteristics, phenological parameters, seedling density, sapling density, and tree density using Structural Equation Modelling (SEM). The study revealed an immediate association between climate and leafing (Path Coefficient: -0.67; T: 9.374; p < 0.01), flowering (Path Coefficient: -0.61; T: 2.981; p < 0.01), and fruiting (Path Coefficient: -0.67; T: 3.51; p < 0.01). The sequential association between seedling and sapling density and forest structure was also significant (p < 0.5). However, these were found to have no direct link with phenology (T < 1; p > 0.05) which has been assumed to be the outcome of anthropogenic activities in the forest having an impact on the system. Comparatively, synchrony of fruit senescence and synchrony of flowering were the principal events that supported regeneration more than others, each accounting for 79 % and 74 % of their data, respectively. On the other hand, the monthly minimum temperature (contributing 97 % of data) was a key contribution to the principal component (PC1) and was primarily responsible for triggering the phenological cycle. Most of the important phenophases were seasonal (Rayleigh's Z varied from 10.93 to 50.01; p < 0.01) except the fruit initiation (Rayleigh's Z = 0.48; p = 0.2). Most of the species (72 % of all species) had regeneration densities that were corresponding to their competitive scores. Similarly, density of adult tree species proportionated with their density in regeneration stage (sapling and seedling), supporting the research hypothesis. However, several deviant species suggested that the system was affected by a wide range of other factors. This is the first study of its kind to evaluate the critical ecological processes together, and recommends further investigation across different woodland ecosystems to deepen understanding of forest functioning.