My location is India (this is to mention the context). The question I submit here is a common man's query (the level of this question and the expected answer).

Water is essential for the growth of plants and trees. Why does then autumn follow the rainy season? When the rainy season brings so much water, which is essential for the growth of plants, why doesn't spring follow the rainy season?

  • $\begingroup$ India is a rather large place, so I suggest you pinpoint your state? Also, have you read up on the monsoon, and why/how it occurs? $\endgroup$
    – Erik
    Aug 25 '20 at 4:32
  • $\begingroup$ It is different for different parts of the world. In south-eastern Australia, winter is the rainy season so it is followed by spring. It depends on the weather patterns and I don't think the weather cares what grows. However, the native plants will adapt to make the most of what they get. $\endgroup$
    – haresfur
    Aug 25 '20 at 4:41
  • $\begingroup$ @Erik i think indians learn about their seasonal air pressure from school when they learn to spell. The deciduous habit is a paradox though. onlinelibrary.wiley.com/doi/abs/10.1111/… $\endgroup$ Aug 25 '20 at 5:13
  • $\begingroup$ @aliential Yes sir. The apparent paradox is causing the confusion. $\endgroup$
    – user343802
    Aug 25 '20 at 6:36

The precise reasons for leaf shedding after monsoon aren't well known and studied, but there are vague reasons like optimising use of light and warmth for max photosynthetic gain. So the tree has a heavy load of leaves to grow fast in monsoon, and it fast depletes the groundwater if it keeps the leaves in the dry season. read the conclusion here: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1466-8238.2006.00213.x

Trees need to store reserves to allow their survival during winter and for bud flush and leaf growth in the following spring.

Generally it takes 2 weeks or a month for a deciduous tree to prepare dormancy/sleep time, to gather all the nitrogen, glucose and nutritive elements from their leaves. If the plant keeps on growing when it's leaves are adapted to massive rainfall, it may lose the green leaves rather than gather useful elements and prepare for dormancy.

i.e. from this image you can see the winter stored sugar being used to grow new leaves, for this tree the spring is in april: enter image description here

There's some interesting facts about leaves here: https://en.wikipedia.org/wiki/Autumn_leaf_color#Function_of_autumn_colors

  • $\begingroup$ Thanks a lot for the explanation and the link. It is mentioned in the paper (that the link opens) that "Implicitly, rainfall periodicity, i.e. climate, is not the principal determinant of vegetative tree phenology". Does it mean that trees follow their own cyclic pattern, which is mostly independent of the seasonal changes? $\endgroup$
    – user343802
    Aug 25 '20 at 6:45
  • $\begingroup$ Yes it uses over-complicated words to sound clever. In proper |english he said: "The seasonal rainfall timing and the climate generally appear not to be the main factor that govern the deciduous periods of the trees" ... And actually that statement is a bit wrong. He should say "The short-term rain and temperature levels are implicity not the main determinant of the deciduous timing, the longer term physiology of the tree is more important" ... I'll add a bit to the answer. $\endgroup$ Aug 25 '20 at 7:32

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