Emerging paradigms of tree phenology in dry tropics

The tropical dry forests constitute a mosaic composed of several phenological functional types adapted to seasonal drought in different ways. Various functional types differ with respect to phenological timing and triggering factors, water relations, extent of deciduousness (∼ leaflessness), etc. Duration of deciduousness in tropical trees (reflecting integrated effect of seasonal drought, tree characteristics and soil moisture conditions) is related to leafing patterns and resource use rates. Vegetative and flowering phenology of trees in dry tropics is primarily affected by the periodicity of rainfall and soil water availability. Occurrence of leaf-flushing as well as flowering during summer in majority of Indian tropical trees, when drought is severe, seems to be a unique adaptation to survive under strongly seasonal climate having a short growth promoting wet period and a long growth constraining dry period. The key phenological themes that need research focus in the dry tropics are: duration of deciduousness, timing of vegetative bud break, leaf strategy, water relations, seasonal flowering types and asynchrony. Analysis of functional types based on the duration of deciduousness and timing of bud break may enable better assessment of future climate change impact. There is a need for long-term quantitative documentation of tree phenological patterns in India through a phenological station network in diverse climatic/vegetational zones.

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