Due to severe frosts, Acacia nilotica was found along river course and depression.
However, due to climatic change, frosts occurrence are no more common in upper Sindh and
Acacia nilotica grows in all such areas along the river where moisture is available substantially.
Mature trees of nilotica, the last one's I saw were in Sindh along the Indus river about forty years back. Huge trees.fifty feet or so with a spread about the same in Khannoot forest, district Dadu. It was deep shade under them. I don't think any have survived the greed of man in this area.
What happens is, the trunk and major branches over time lose their thorns but I wont call them thorn less. The minor branches and new growth are still armed.
Babbul and Kikkar are the same tree, Acacia. Babbul is in Urdu/Hindi, same language different names. Depends on which side of the border you are. Kikkar is in Punjabi/Sindhi/Pashto vernacular. Which boils down to this side of the border, with half of Punjab on that side. Urdu/Hindi is the main spoken language but it is evolving into two taking into its folds the local dialects so divergence over time is taking place.
Now when you enter babbul, then the trees from central India predominate. When you enter Kikkar, trees from the Western part predominate. This nilotica started from the Nile area, why don't you check Egypt from where the journey started? See what they have to say, then we have Arabia, Iran, Afghanistan where all it rested on its long journey. By the time it reached us it became subs. indica.
Regards,
Masud.