EPOW - Ecology Picture of the Week

Tree Canopy, Evergreen Forest
Ntchisi Forest Reserve, Malawi, Africa

Explanation:   Look closely at the photo above.  We are standing in a forest reserve in Ntchisi, in the country of Malawi, Africa.  This is an evergreen tropical forest.  Do you notice anything odd about the tree foliage?

From time to time, I have observed something curious in tropical forests of the world.  Notice how there seems to be a suture line, a narrow gap that separates the foliage of one tree from that of the adjacent tree.  

What could cause this?  I have no definitive answer, but some speculation ... Perhaps there are allelopathic effects, where one plant produces a chemical that excludes nearby plants.  Or maybe there are beneficial, herbivorous insects that are consume foliage from the adjacent tree when it grows close by, and thus defend one tree from the other.  

Whatever the cause -- and perhaps causes vary among locations and tree species -- one if not both of the trees could benefit from such a "territoriality" of their air space, by reducing competition for light and growing space resources. 

But for now, this remains a bit of a mystery.  A mystery of the forest canopy.
  

 
Another example of the "canopy suture line mystery" ... 
this one from a tropical rainforest of northern 
Queensland, Australia, in Lamington National Park.