United States Department of State
People and the Temperate Region A Summary of Research from the United States Man and the Biosphere Program 1991
Editedby Peter F. Ffolliott
School of Renewable Natural Resources University of Arizona Tucson, Arizona
and
Wayne T. Swank
Southeastern Forest Experiment Station USDA Forest Service Otto, North Carolina
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UnitedStatesManandtheBiosphereProgram tl~ ~ -- . --- Forest and Meadow Communities of the Three Sister Biosphere Reserve
Charles B. Halpern, Bradley G. Smith, and Jerry F. Franklin
TheThreeSistersBiosphere Reserve Objectives encompassesnearly 100squarekilometers of virtually undisturbed land stradling the crest of the central CascadeMountains of Theobjectives of this study were to: Oregon. Although coniferous forests dominate, an array of other ecosystems -Describe the composition, struc- createsa diverse picturesquelandscape ture, and distribution of major (Figure 1). The Three Sisters Biosphere forest and meadow communities, Reserve, established as a primitive area in as well as their principal environ- 1933, was selected in 1974 to serve as a mental controls. control for the nearby experimentally oriented H. J. Andrews Biosphere Reserve. -Establish a series of permanent Ecological information about the Three sample plots for examining long- Sisters Biosphere Reserve was needed to term changes in the composition establish a basis for future comparative and structure of these communi- research with the intensively managed H. J. ties. Andrews Biosphere Reserve.
FIGURE 1. Forest and meadow ecosystems in the Three Sisters Biosphere Reserve in the central Cascade Mountains of Oregon. 3 - I - . ~ Methods boundaries between forest and I meadow communities, was installed Field sampling, conducted over a 3- (Figure 2). Sites were selected to year period staning in 1981, documented represent a diversity of types and to the composition, structure. and distribution encompass the variety of tree of forest and meadow communities in the invasion patterns observed. Three Sisters Biosphere Reserve. In the summer of 1983, a series of permanent ·Along ecotone transects, four types transects were established to assess long- of data were collected: term changes in vegetative composition and structure across boundaries between -composition and structure, these forest and meadow communities. including in species frequency and canopy cover; · Forest vegetation was sampled using a reconnaissance method, in -location, diameter, height, and which compositional characteristics aQ:eof all trees. Smaller trees of forest sample plots were assessed that could not be cored were aged through estimates of canopy cover by counting terminal bud scars. of each vascular plant species. Structural characteristics were -soil characteristics and environ- examined throU!!hthe identification mental features; of height and diameter size class distributions for all tree species. -photographs taken at perma- nently located points for future The age of forest stands was esti- comparison. mated with increment cores taken from one or two dominant seral Reconnaissance data were utilized to trees within each sample plot. develop community classifications for Environmental features (elevation, forest and meadow vegetation, and to slope and aspect, landform, and identify environmental features influencing topography) were recorded and the composition and distribution of these imponant soil characteristics communities. Cluster analysis and ordina- (panicle size distribution and litter tion techniques were used for this purpose. composition) were described. Additional observations on fire and Analyses of ecotone transect data geomorphic disturbance, as well as focused on the spatial distribution of tree other distinctive features not ad- species by size and age classes, and the dressed in the reconnaissance data, composition of the corresponding forest were recorded. understory and meadow vegetation. ·Meadow communities, comprised of bog, fen, pumice flat and "rock garden" communities, were exam- Findings ined using techniques similar to Imponant findings from the forest those employed for forests. communities sampled in the Three Sisters Sample plots were characterized in Biosphere Reserve included: terms of species composition and environmental features, with special · A total of 162 vascular plant attention given to the mosaic of species were identified and 16 vegetative types within each meadow. major forest plant communities were defined. The plant communi- ties fell into five forest Series de- Baseline information for future · fined by the climax tree species- examination of vegetative change, Pseudotsuga menziesii, Tsuga obtained from a series of perma- nently marked transects across the heterophylla, Tsugaheterophylla- 4 FIGURE 2. Baseline infonnation on vegetation was obtained from pennanently marked transects located across the forest and meadow community bolDldary.
Abies amabilis, Abies amabilis- The forests were relatively young, Tsuga mertensiana, and Tsuga between 175 and 250 years of age, al- mertensiana. though there also were remnant old-growth forests of 400 to 500 years. Most of the · The distributions of the Series were stands at lower elevations have burned at correlated with environmental least once since the 1840s. Forests in- changes associated with increasing creased in average age with elevation. elevation, that is, decreasing tem- Old-growth forests were restricted largely perature, increasing precipitation, to the subalpine zone. I greater snowpack, and shoner growing season. Within each Findings in meadow communities Series, secondary environmental included: gradients, such as soil moisture and temperature, influenced the compo- · A total of 384 vascular plant spe- sition and distribution of plant cies were identified and 23 montane communities. and subalpine meadow communi- ties were defined. · The frequency and distribution of disturbances, such as wildfire, were · The composition, structUre,and imponant in understanding the distribution of meadows were structure of forest ecosystems. correlated with landform and I
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topography, elevation, hydrological Implications features, and soil characteristics. For simplicity, meadow communi- Information from this study provided ties can be grouped into three the first extensive body of data on the categories: composition, structure, and distribution of ecosystems in the Three Sisters Biosphere -Meadows occurring on flat Reserve. The study results included: terrain or in basins-Meadow communities on these sites · a classification and a key to forest experience either a water table communities in the biosphere persisting at or above the soil reserve; surface, or a deep and persistent snowpack that keeps the soils · a general description of the natural moist through the short growing disturbance history in the forested season. These communities portion of the biosphere reserve; typically are graminoid-domi- nated. · a classification of montane and sub- alpine meadow communities; and -Meadows along steeply sloping landforms-Here, soils range · a series of permanent transects for from deep, loamy, and well- examining long-term changes in the drained, to shallow, rocky, and composition and structure of forest- potentially droughty. These meadow communities. meadows, which typify the highly dissected terrain of the Forest community and fire history western portion of the Three information from the relatively untouched Sisters Biosphere Reserve, are ecosystems of the Three Sisters Biosphere forb-dominated communites. Reserve provided a baseline for compari- son with the experimentally-oriented H. J. -Meadows along the gentle slopes Andrews Biosphere Reserve and with other and rolling plains adjacent to the intensively managed areas along the west- base of the region flanking the ern slope of the Cascades. Furthermore, bases of the Three Sisters the forest community classification was peaks-On these sites, soils vary compatible with those developed by the from shallow and gravelly to USDA Forest Service on adjacent natIOnal deep and pumicey. These forest lands. meadows are dominated by a Despite their ubiquity and aesthetic diversity of graminoids, forbs, appeal, meadows in the Three Sisters and low shrubs. Biosphere Reserve, and in the Pacific Northwest in general, have not been de- · The patterns of tree invasion into scribed adequately. These community these meadows were diverse. studies provide an extensive data base on Hydric, mesic, and xeric meadow the composition, structure, and distribution communities have all experienced of meadow communities in the central encroachment. Forest-meadow Cascade Range. Data obtained from boundaries range from abrupt to future remeasurements of forest and diffuse. Tree invasion has oc- meadow ecosystems will help in obtaining curred in waves, in clumps, or as a better understanding of the dynamics of isolated individuals. A majority of these and similar ecosystems that span the these trees became established Sierra-Cascade Axis. between 1930 to 1970.
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