Another vote for a quality handsaw. For sample collection eschew the large toothed versions in favor of one of the finertoothed and smoother cutting choices.
Another vote for a quality hans saw. Powered reciprocating saws are designed to be operated two handed while standing with both feet firmly on the floor. Not very feasible in a tree or on a ladder. Attached is a picture of a cut on my left forearm I recieved while using a reciprocating saw on a ladder removing rain gutters.
Pat.