Ecosystem Studies in the Subalpine Coniferous Forests of Wyoming

An overview is presented on recent ecosystem studies in the Medicine Bow National Forest and Yellowstone National Park. Most of the research has focused on lodgepole pine forests. Hydrology, leaf area development, decomposition, nutrient dynamics, soil chemistry, landscape ecology, and the effects of tree harvest, fire, and mountain pitie beetles have been emphasized. The subalpine elevations of Wyominpmountain ranges are characterizcd by a mosaic of meadows, lakes, and forests dominated by various mixtures of Iodgepole pine ('Pinus corztma var. Iatifolili Eqelm.), subalpine fir (Abies Iasiocarpa [Hook.] Nutt.), Engelmann spruce (Picea engebnannii Parry ex Eagelm.), and aspen (Poprrlirs rremu1oidc.s hiichx.). As in other parts of the Rocky Mountains, vegetation patterns are determined by environmental factors associated with elevation, topographc position, soil charxreristics, acd the history of disturbances including l i e , logging, and outbreaks of the mountain pine beetle iDc.rtdrocronoirspri'i.rclsncl Hopk.). On the warmer and drier sites lodgepole pine appears to form a stable community that persists until fuel accumulation makes the next fire inevitable (Romme and Knight 1981, Despain 1983). Elsewhere spruce and fir are the climax species, sometimes aeveioping in the understoq of pimeer !odgepolt pine or aspen forests but in other cases invading directly foilowing a burn or some other disturbance (Stahelin 1943, R o m e and Knisht 1981). For many years research on the subalpine forests of Wyoming was focused on species composition, classification, and succession. Such studies are essential for providing the understanding required for sound resource management, but many questions pertaining to nutrient cycling and water flows were not being addressed. Of course, research at the nearby Fraser Experimental Forest was providing good information on forest hydrology, but more remained to be done. Recognizing the importmce of such research for management, my celleagues and I began to study the subalpine forests of Wyoming from an ecosystem perspective. In this paper I will provide an oveniew of some of our results thus fix. Most of our research thus far has focused on forests dominated by lodgepole pine and has been done at the stand level rather than at the scale of the watershed. Originally we lProfessor, Department of Botany, Universityof Wyoming, Laramie, WY 82071. had hoped to find a watershed in Wyoming that could be studied ia the manner of the Fraser or Hubbard Brook watersheds, but during the search we concluded that our Watersheds were so heterogeneous ('in terms of vegetation, soils, and geologic substrate) that it would be difficult to evaluate biotic effects on water and nutrient fluxes -one of our primary interests. Instead we seiected homogeneous stands of afewhectares as our ecosystcms.Suchstaads had the advantage of being cioser to the scaie of an actual timber sale than whole watersheds, and we hoped that they wouid provide the opportunity to examine more precisely the effects of vegetation structure on ecosystem processes. Studying stands instead of watersheds has its problems (Knieht et al. 1989, but we felt they could be resoived in the relatively simple lodgepole pine forest. Most of the research has been done in the !k:dich.e B w N~ztional Forest, 50 km west of Laramie, but severai studies were conducted in Yellowstone and Grand Teton National Parks as well. Many individuals have helped in the development of our research, hciuding colleagues at neighboring universities and with federal agencies, but the following individuals deserve special recognition: James F. Reynolds, Ned Fetcher, William H. Romme, Steven W. RuMing, Timothy J. Fahey, John A. Pearson, Joseph B. k'avitt, and Howard E. Haemnierle. These graduate students, listed in order of degree completion, worked long hours for little reward other than a chance to make a contribution to forest science. 'To a very large extent, it is their results that are highlighted in this overview. I am also especially grateful for the cooperation extended to us by the staff of the Medicine Bow National Forest. Our research has been funded by the National Science Foundation, Wyoming Water Research Center, University of Wyoming National Park Service Research Center, Department of Interior (Office of Water Research and Technology), and the Department of Agriculture (U. S. Forest Service, Rocky hlcluntain Forest and Range Experiment Stationj.