If you have limbs to cut that are above your shoulder height use a specially designed saw with extended reach to perform those operations.
No matter what the job, whether it's a tree limb on the ground, partially suspended above the ground or a standing tree, you must always evaluate the job and the dynamics of the situation before you begin cutting.
As you are in the process of cutting wood, the dynamics of the tree, meaning weight and balance can change. With the larger and heavier limbs, there could be a chance that the tree will shift its position as the weight of those limbs are taken away. Make sure that you evaluate this weight prior to begin the cutting and that you position yourself and plan your work accordingly.
There are some basic rules to follow when limbing a tree on the ground.
First always begin limbing, the base of the tree, moving your way upward. Whenever possible, keep the log between you and the limb you are cutting. Make sure that you have good solid footing at all times. Never stand on the log and never hold the saw with one hand when cutting. Always hold the saw with both hands with a firm grip, fingers and thumb fully engaged around the handles. If the log is located on a slope, always stand on the up hill side of the log so if it rolls, it rolls away from you. If the log is supported by limbs on the other side of the tree, leave these limbs for last as they will help support three during your work.
Be cautious when cutting a limb from the bottom or under bucking. The limb may tend to close in on the cut, resulting in a pinched chain and guide bar. If this happens, turn off the saw and remove the saw from the cut.
This is a limb under pressure refer to as a spring pole. These can be very dangerous as they can spring back toward you with great amount of force when cut. This can cause you to lose control of the chainsaw or result in severe or fatal injury. Be very cautious when cutting spring poles. Release the tension by making multiple shallow cuts on the outside of the arc with you standing at the center of the arc.