Abstract
BackgroundIn tropical dry forests, variation in understory light availability due to season and canopy tree density could be a governing factor in establishment and growth of tree seedlings. Species with varying life history traits are expected to respond differentially to such heterogeneity. We investigated the response of seedlings of four tree species in a tropical day forest in relation to spatiotemporal variability of light. We attempt to explore the role of leaf attributes in explaining intra- and inter-specific variations in relative growth rate. Four study sites, each with three contrasting canopy conditions, were selected along a soil moisture gradient. Seedlings of four tree species (viz., Acacia catechu, Bridelia retusa, Lagerstroemia parviflora, and Shorea robusta), varying in life history traits, were monitored for seasonal variations in growth traits across canopy condition and sites for 2 years.ResultsWe observed a larger variation in leaf attributes for pioneer species. A. catechu showed highest mean values for leaf dry matter content, leaf nitrogen concentration, leaf phosphorus concentration, net stomatal conductance, net photosynthetic rate, and relative growth rate in high light conditions. S. robusta and B. retusa demonstrated highest mean values for all the leaf attributes (except leaf dry matter content) in low light conditions. However, intermediate values for leaf attributes were observed in L. parviflora which preferred moderate light conditions.ConclusionsSeasonal variations in light availability at the forest floor appear to play an important role in the establishment and growth of tree seedlings in seasonal dry forests. Leaf attributes can be used to explain intra- and inter-specific variation in response to light availability. Leaf attributes in combinations can be used to predict relative growth rate of tree species in tropical dry environment, which apart from soil moisture is also determined by light availability due to seasonal changes and canopy tree density.
Highlights
Amount of light available on the forest floor has been reported as a strategic environmental regulator which governs intrinsic growth behavior of residing plant species (Augspurger 1984; Walters and Reich 1996; Bhadouria et al 2018)
Growth period of tropical dry forest (TDF) tree seedlings is restricted to the rainy season mainly due to adequate soil moisture availability, which provides optimal conditions for seedling growth
As dry deciduous forest in India is renewed by leaf flushing in the dry and hot pre-rainy seasons (Singh and Singh 1992), the lush green foliage during the subsequent rainy season reduces the light intensity reaching to seedlings growing understory and may produce a limiting light condition for their growth
Summary
Amount of light available on the forest floor has been reported as a strategic environmental regulator which governs intrinsic growth behavior of residing plant species (Augspurger 1984; Walters and Reich 1996; Bhadouria et al 2018). Seedlings growing in open canopies or at forest edges experience high light intensity It demonstrates the heterogeneity in environmental conditions during the most favorable period for the growth. During the dry season, soil water availability declines rapidly, inflicting the growth and survival constraint on tree seedlings (Gerhardt 1996). In these conditions, the shady environment provides a habitat of vital significance providing higher soil moisture availability and having reduced transpiration load (Lieberman and Li 1992; Huante and Rincón 1998; Gerhardt 1996). Seedlings of four tree species (viz., Acacia catechu, Bridelia retusa, Lagerstroemia parviflora, and Shorea robusta), varying in life history traits, were monitored for seasonal variations in growth traits across canopy condition and sites for 2 years
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