Below is a Monster Hunter Portable 3rd Bow Tree image chart.
Bows are a very flexible ranged weapon, useful in group hunts as well as soloing. They possess the range to break off various parts on a monster otherwise unreachable to the melee hunter and, with charged attacks, the power to exploit any weakpoint the monster might have. Coatings, especially the Power Coating, is critical to the success of a bow-user. Like bowguns, distance also plays an important role on the damage caused to a monster.
This image chart is specifically a Bow Tree for Monster Hunter Portable 3rd.