In 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. We 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. Seasonal 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.

中文翻译：

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可用光对热带干旱森林四种树种叶片特性和幼苗生长的影响

在热带干旱森林中，由于季节和冠层树木密度而引起的林下可用光度的变化可能是树苗生长和生长的主导因素。预期具有不同生活史特征的物种对这种异质性的反应不同。我们调查了热带雨林中四种树种的幼苗对光时空变化的响应。我们试图探索叶片属性在解释相对生长速率的种内和种间变化中的作用。沿着土壤水分梯度选择了四个研究地点，每个研究地点都具有三个相反的冠层条件。四种树种的幼苗，其生活史特征各不相同，监测了2年间不同冠层状况和地点生长特性的季节性变化。我们观察到先锋物种的叶片属性有较大的变化。在强光条件下，A。catechu对叶片干物质含量，叶片氮浓度，叶片磷浓度，净气孔导度，净光合速率和相对生长速率显示最高平均值。在弱光条件下，稳健链球菌和维氏梭状芽胞杆菌的所有叶片属性（叶片干物质含量除外）均显示出最高平均值。但是，在小花乳杆菌中观察到叶片属性的中间值，这优选中等光照条件。森林地面光能利用率的季节性变化似乎在季节性干燥森林中树苗的建立和生长中起着重要作用。叶片属性可用于解释种内和种间响应光利用率的变化。叶片属性的组合可用于预测热带干旱环境中树木物种的相对生长速率，除土壤水分外，还取决于季节性变化和冠层树木密度所带来的光照可用性。