|I like how you write this opening chapter in the third person to describe how the people of this world thought and spoke. Please see the below for recommended changes:
1) He dared climb higher, leap farther, and to less solid branches, than any other of the warrior. --- Typo: "warriors"
2) It was said that he was more comfortable leaping tree to branch to leaf to twig, than even the small, nut and seed gathering chitter sailers --- It should be "sailors" and a period is needed.
3) Acknowledged as the best example of a high demand, high performance population. He was sure to be announced soon as an heir to a tribe. That tribe's warrior representative amongst the Runners. --- Only the last period should be there. The other periods should be replaced with commas to prevent these fragments.
4) The rain began to fall, as expected. Fat drops, hitting with a palpable force on the top layers, even having some fair strength driving them, fat and pounding, to his height. --- The first period should be replaced with a comma to avoid having a fragment here.
5) When the storm was so close to him that even the thicker branches able to support a woodcutter's weight, standing solid, were weaving and shaking to the point he was having trouble finding footing along them, much less purchase enough to allow his normal fleet run. Ai'Liel came to a decision. --- Please see #4.
6) As the sky fire was cracking so close that the flash and the bursts of sound came almost simultaneously, he began lashing himself to the tree, hampered by the cutting winds. --- It should be spelled "latching."
7) Ai'Liel could feel the whole tree he was lashed to thrumming with the power transferred to it. --- This should be "latched" here.
8) For an interminable time, Ai'Liel rode the storm, in this manner, whipped, flayed, scoured by wind and rain, and the small debris carried on each in its maddened rush. The storm seeming to draw more and more on the pure and raw energy of the Brown Father, from whence all life grew and to all returned, in some form, to be born again, anew and different. --- Please see #4.
9) There was an incessant thrumming throughout this part of the forest, born of the complicated and ongoing vibrations of living wood strummed by the violent fingers of the wind, playing its strings on that which withstood its onslaught, and percussion with skyfire and falling branches, Water making various accents to the dramatic, and brutal symphony. --- The word "water" should not be capitalized.
Good luck and write on!