Fraser fir adelgid mortality. The decline of the Fraser fir in the southern Appalachians has contributed to loss of moss habitat which supports the spruce-fir moss spider. The Fraser fir is an endangered species. Threats include climate change, balsam woolly adelgid and destruction of trees for Christmas trees and timber. Although not important as a source of timber, Fraser fir is widely used as a Christmas tree. Its mild fragrance, shape, strong limbs, and ability to retain its soft needles (which do not prick easily when hanging ornaments) for a long time when cut make it one of the best trees for
WAVL tree WAVL tree In computer science, a WAVL tree or weak AVL tree is a self-balancing binary search tree. WAVL trees are named after AVL trees, another type of balanced search tree, and are closely related both to AVL trees and red–black trees, which all fall into a common framework of rank balanced trees. Like other balanced binary search trees, WAVL trees can handle insertion, deletion, and search operations in time per operation. WAVL trees are designed to combine some of the best properties of both AVL trees and red–black trees. One advantage of AVL trees over red–black trees is that