College of Letters & Science

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The College of Letters and Science, the largest center for learning, teaching and research at Montana State University, offers students an excellent liberal arts and sciences education in nearly 50 majors, 25 minors and over 25 graduate degrees within the four areas of the humanities, natural sciences, mathematics and social sciences.

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    Vegetation Distribution and Production in Rocky Mountain Climates—with Emphasis on Whitebark Pine
    (International Workshop on Subalpine Stone Pines and Their Environment: the Status of Our Knowledge, 1992) Weaver, T.
    The distribution and production of vegetation on the altitudinal J gradient (grassland-forest-alpine) was plotted against climatic parameters to evaluate hypothetical controlling factors. (1) Whitebark pine (Pinus albicaulis) is likely excluded from higher zones by a cool growing season or wind-induced drought. It is probably not excluded by low temperatures occurring during its hardening, hard, or dehardening seasons. (2) While the lower physiological limit of whitebark pine is probably set by drought its lower realized limit is directly set by subalpine fir (Abies lasiocarpa) and lodgepole pine (Pinus contorta) competitors and indirectly set by factors that control their distribution. (3) The upper limits for most other dominant species are probably set by growing season temperature. The lower limits are likely set by competition down to the cedar-hemlock (Thuja plicata/Tsuga heterophylla) zone and by drought in drier areas. (4) Production is strongly correlated (r 2 = 0.86) with growing season length (soil thawed season minus dry soil days). Multiplying season length by average temperature did not improve the growing season predictor, perhaps because vegetation at each altitude is especially adapted to temperatures in its zone.
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    Climates Where Stone Pines Grow, A Comparison
    (International Workshop on Subalpine Stone Pines and Their Environment: the Status of Our Knowledge, 1992) Weaver, T.
    ------ Abstract-While stone pine climates are similar adapted to relatively moderate climates may be excluded from, species the ranges of congeners by more severe climates, and species with longer warm-moiBt growing seasons are probably more productive than congeners. Absolute low/summer average/absolute high temperatures for stone pines listed in order of increasing absolute low temperature are Pinus sibirica (-65/13/37 °C), P. pumila (-52.19/36 °C), P. koraiensis (-42/1s1/36 °C), P. albicaulis (-3419/29 °C), and P. cembra (-23/8/27 °C). The Walter drought index shows little stress in stone pine forests despite large differences in summer/winter precipitation: in order of increasing summer rainfall, precipitation is P. albicaulis (102.I 829mm), P. pumila (1421.264mm), P. sibirica (1871245=), P. cembra (3231616mm), P. koraieT18is (3941242mm). Estimated thawed-soil growing season increases from P. albicaulis (4.5mo), throughsP. pumila (4.6mo), P. sibirica (5.5mo), and P. cembra (6.3mo) to P. koraiensis (7.8mo); growing seasons of the first three trees could be shortened by drought.
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    PLANTS ESTABLISHING IN ROCKY MOUNTAIN ENVIRONMENTS-- a manual for choosing native species for revegetation
    (Montana State University, 1995) Weaver, T.; Gustafson, D; Lichthardt, J
    Species which have established naturally on a disturbed site in a given environment-- climate and disturbance level (defined below)-- are good candidates for revegetation plantings in that environment. On this basis we recommend native plants (grasses, forbs, and shrubs) for revegetation plantings, if they occur on at least half of the sites sampled in the environmental type and cover at least 1% of the ground there. We also list exotic plants establishing on once disturbed roadside sites; if these plants do not invade native vegetation they might, under some circumstances, be used for revegetation The environmental types considered include dry grasslands (BOGR/STCO and AGSP/BOGR), moist grasslands (FESC/FEID and FEID/AGCA) sagebrush (ARAR/FEID and ARTRVAS/FEID) , warm dry forests (PSME/ SYAL and PSME/PHMA), warm moist forests (POTR/CARU, THPL/OPHO, TSHE/CLUN, ABLA/CLUN), cool forests (ABLA/XETE, ABLA/ARCO, and ABLA/VACC), mountain meadows (FEID/AGCA, listed above) and alpine (DESC/CARX) . In each environment plant performance is contrasted across five disturbance types: continually disturbed types (roadshoulders and the adjacent ditch slope), once disturbed sites (roadcuts with organic matter removed and cleared right-of-way without organic matter removal), and undisturbed late seral sites.
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    Evaluating the land: evolving perceptions of landscape in Gallatin Valley settlement, 1864-1918
    (self-published, 1997-05) O'Neill, Maire
    This study investigates how people have viewed the environment and the terrain of the Gallatin Valley through a cross section of time. The period during which the region was settled is explored for its impact on the present palimpsest of the landscape. The choices people made about where to farm and where to site their houses reveals much about their perceptions and attitudes towards the land. What people thought about its potential and its threats are reflected not only in their journals, but in the physical markings they have made in the form of buildings, fences, roads, and irrigation ditches.
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    Exotic invasion of timberline vegetation, northern Rocky Mountains, USA
    (1990) Weaver, T.; Lichthardt, J.; Gustafson, D.
    Thirty-five exotic species were found in vegetation characteristic of Northern Rocky Mountain timberlines. At least 20 percent were intentionally introduced along road-sides. The diversity of invading exotics declined from subalpine to alpine vegetation. While exotic diversity generally increased with increasing disturbance, severe trampling excluded some species from road-shoulder sites. The exotics of greatest concern to wildland managers are Phleum pratense (timothy) and Poa pratensis (Kentucky bluegraass) because they establish widely, spread vigorously, and usually escape early detection. Control of any exotic should involve its eradication and simultaneous introduction of desirable competitors to minimize reinvasion.
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    Seeing whitebark pine in a northern Rocky Mountain (USA) landscape: notes for a field trip
    (1990) Weaver, T.
    The changing role of whitebark pine (Pinus albicaulis) along an altitudinal gradient typical of the Northern Rocky Mountains (USA) can be seen from the gondolas at the "Big Sky" resort near Bozeman, MT. Whitebark pine appears mostly as seedlings in the lowest zone (7,500 to 8,500 ft), becomes increasingly important in the canopy between 8,400 and 8,900 ft, assumes climax dominance in the woodland zone (8,900 to 9,300 ft), and maintains that dominance to treeline. On this gradient the mature tree's growth form changes from tall-lyrate, to shorter-spherical, to krummholz. The tree is seral in the lowest zones; frequent fires exclude it from canopies in the lowest zone, while low fire frequency gives it subclimax status higher (8,400 to 8,900 ft) in the zone dominated by subalpine fir (Abies lasiocarpa) at climax. Above 8,900 ft, whitebark dominates woodlands (formed, probably, when subalpine fir is excluded by cold) and krummholz (due, probably, to winter desiccation). Mountain pine beetles (Dendroctonus ponderosae) have killed much of the lodgepole (P. contorta) and whitebark pine in the area, and whitebark groves tend to be ringed with dead trees because the especially vigorous trees at grove edges are most susceptible. Cirque bowls on Lone Mountain demonstrate an inverted timberline at which conifers disappear downward, probably due to spring frosts.
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    Berry production in three whitebark pine forest types
    (1990) Weaver, T.; Kendall, K.; Forcella, F.
    In the whitebark pine lwhortleberry (Pinus albicaulis/Vaccinium scoparium) habitat type of southwestern Montana, whortleberry plants produced seven to 69 berries I m• X yr in 1974. In subalpine fir (Abies lasiocarpa) habitat types of northwestern Montana, huckleberry plants (Vaccinium globulare) may produce from 13 to 228 berries I m2 X yr. While removal of competing trees increases production, thinning the understory apparently reduces berry production in direct proportion to the shrubs removed; there is no compensatory production indicative of shrub-shrub competition in fully vegetated plots. Fifty- to 100-fold variation in production among years in Vaccinium globulare berry production is attributed to variation in weather conditions.
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    Biotic and microsite factors affecting whitebark pine establishment
    (1990) McCaughey, Ward W.; Weaver, T.
    To enhance establishment of future whitebark pine (Pinus albicaulis) forests, information is needed on the physical and biological factors affecting whitebark seed germination and seedling establishment. This paper summarizes the first-year results of field examinations designed to evaluate predator and seedbed factors affecting whitebark pine establishment. Predator effects were estimated by recording seedling emergence under four levels of predator exclusion (free predator access, rodents excluded, birds excluded, and both rodents and birds excluded). Rodents ate or removed 100 percent of available surface-sown seeds. Emergence was higher on plots excluding rodents only and significantly higher on plots excluding rodents and birds. Seedling emergence did not differ significantly between mineral (although numerically higher) and litter seedbeds. The effects of three seedbed factors were also examined by comparing seedling emergence under three light levels (open, 25, and 50 percent shade cover), two seedbed conditions (mineral and litter), and two sowing depths (on surface and 0.8 to 1.6 inches beneath surface). Buried seeds had significantly higher emergence rates than did surface-sown seeds. Even though the first season was hot and dry, 78 percent of seedlings survived.
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    Effects of temperature and temperature preconditioning on seedling performance of whitebark pine
    (1990) Jacobs, J.; Weaver, T.
    Four experiments explored the effects of temperature on the germination and seedling performance of whitebark pine (Pinus albicaulis). While 1 month of stratification increased germination from 5 percent to about 40 percent, longer stratification periods (to 8 months) did not improve germination. Germination occurred throughout the 10 to 40 °C range with a broad optimum near 30 °C. Root growth occurred throughout the 10 to 45 °C range with an optimum near 30 °C. Long exposure (5 months) to low temperature (1.5 °C) lowered the temperature threshold for both germination and root growth. The apparent temperature range (perhaps 0 to 35 °C) and optimum (20 °C) for net photosynthesis at light saturation were lower than for germination and growth. While no preconditioning effect of light level (200 to 800 uE I M2*S) on the photosynthetic capacities of mature leaves was seen, photosynthesis increased progressively from needles preconditioned with winter, spring (5 °C day to 5 °C night), summer (15 °C day to 5 °C night), and abnormally warm (25 °C day to 15 °C night) temperatures.
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    Stand development in whitebark pine woodlands
    (1990) Weaver, T.; Forcella, F.; Dale, D.
    Analysis of density data from stands in the Northern Rocky Mountains shows that, while seedlings establish at the rate of over 1,000 I ha x year in whitebark pine-grouse whortleberry (Pinus albicaulis-Vaccinium scoparium) forests of all ages, stem numbers in the canopy thin to 400 at 30 years, 150 at 200 years, and 100 at 300 to 600 years. Indices of productive potential, cover, and total circumference rise to an asymptote at about 100 years. Total basal area rises from 0 to 60 m21 ha at about 200 years, the aggregate basal area of trees with diameters over 20 em rises from 0 to 40 m21 ha at about 250 years, and tree height maximizes (12 m) at 200 years. It is hypothesized that further growth in productive potential (that is leaf and I or root area) is prevented by limited supplies of water or a nutrient, further growth in basal area is prevented by lack of a nutrient (probably not carbon, hydrogen, oxygen, or nitrogen) and further growth in height is prevented by scarcity of water.
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