Interpreting the timberline: An aid to help park naturalists to acquaint visitors with the subalpine-alpine ecotone of western North America

Arno, Stephen

This paper attempts to survey timberlines of western North America in a manner primarily designed to serve public interpreters of natural history, such as park naturalists. Hopefully, this broad discussion of the timberlines will also be of interest to biologists and some members of the public. Much of the discussion is based upon personal observation of timberlines (see APPENDIX). The emphasis of this paper is on trees of the timberline, though of course trees are only a part of the timberline habitat. The professional naturalist must relate a broader sketch of the environment called "timberline" in his particular location. This paper will not attempt to provide all the necessary information about all aspects of timberline. Moreover, it will not outline a precise program that can be followed by naturalists step by step to interpret timberline for the public. This paper is designed to aid naturalists who are employed in many different localities, working under different programs with different limitations and goals. This report provides proposed definitions for the terminology relating to timberlines, a review of the causes of timberline formation, a comparatively detailed description of the timberlines of western North America, a discussion of the various tree species as timberline dwellers, and suggestions regarding the needs for and means of interpreting the timberline. Particular emphasis is placed on the trees of timberline in this report for three main reasons. One is the realization that nothing short of a multi-volume work could discuss all phases of the timberline environment in significant detail. Secondly, since the subject must be restricted in scope, the tree growth at timberline seemed a logical segment of the habit for discussion. That is, tree growth is the most obvious feature of timberline (as opposed to underlying geology, climate, animals, etc). Furthermore, the tree grovrbh expresses the total environmental picture of the location at which it occurs. The final reason for the emphasis on trees here is that despite the fact that trees are an obvious starting point for understanding the timberline, they are often skimmed over briefly in interpretation. It may be that many naturalists and others do not know the very interesting "story" of trees at the timberline (superficially, wildflowers or animals might seem to warrant more attention). Hopefully, this paper will help the naturalist to initiate or improve the discussion of timberline which is presented to the public at his area.