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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Item Distribution of Exotic Plants in the N. Rocky Mountains by Environmental Type and Disturbance Condition(Montana State Univeristy, 1989-06) Weaver, T.; Gustafson, D.; Lichthardt, J.; Woods, B.This report lists seventy-three exotic species found in a systematic sampling of major environmental zones of the Rocky Mountains between the Canadian border and central Wyoming. For each exotic it states the regional distribution, the environmental types (HTs) it occupies (% constancy), the disturbance conditions (DCs) it occupies (% constancy), and its dominance (in terms of% frequency and% cover) in each cell of the HT x DC matrix. Park managers need to develop policy with respect to legally noxious weeds, forage grasses (eg Phleum pratense, Poa pratensis, Bromus inermis, and Dactylis glomerata), and forage legumes (eg Melilotus and Trifolium spp).Item Changes in soils along a vegetational (altitudinal) gradient of the northern Rocky Mountains(Soil Science Society of America, 1979) Weaver, T.As one moves from the warm dry plains of eastern Montana to the cool moist peaks of the northern Rocky Mountains he might pass through a series of native vegetation types: Bouteloua gracilis, Agropyron spicatum, Featuca idahoensis, and Festuca scabrella grasslands; Pinua ponderosa, Pseudotsuga menziesii, and Abies lasiocarpa forests; and alpine tundra (Kuchler 1964, Muggler and Handl 1974, Pfister et al. 1977). It is commonly observed that when one moves up a vegetational gradient he moves up a soils gradient (e.g. Eyre 1963, Whittaker et al. 1968, Hanawalt and Whittaker 1976 and 1977). In the northern Rocky Mountains, Thorp (1931, N Wyoming) observed that organic matter increased, that pH decreased, that the depth to free lime increased and that the thickness of A- and B-horizons increased as he moved up a vegetational gradient similar to that described above. The same trends, as well as a tendency for nutrients to become most available at the grassland-forest boundary, were observed along a similar vegetation gradient in British Columbia (Spilsbury and Tisdale 1944). Such trends correlate well with broad groups in the 1938 Soil Taxonomy (Agricultural Experiment Station 1964 and Nimlos 1963) as well as in the 1977 Soil Taxonomy (Weaver 1978). The objects of this paper are I) to describe the change in soils observed along this gradient in more detail, 2) to consider their genesis briefly, and 3) to consider their importance to plants.Item Root distribution and soil water regimes in nine habitat types of the northern Rocky Mountains(Colorado State University, 1977) Weaver, T.Root distribution and the annual cycle of' soil water availability were measured in nine habitat types of the northern Rocky Mountains. Water stress periods became progressively longer under Abies lasiooarpa forests, Populus trerrruloides groves, Pseudotsuga menziesii forests, Festuoa idahoensis grasslands, Artemisia tridentata shrublands, and Agropyron spioatum grasslands. Water stress periods were longer under Pseudotsuga forests than under adjacent logged areas. Live feeder root biomass (1) was similar under grassland, shrubland, and forest types, (2) increased within a vegetation type with altitude, and (3) decreased at a site with depth. Seral grasslands had less live feeder root biomass than forests in the same habitat type, but climax grasslands and forests were similar in root biomass.Item Cone production in Pinus albicaulis Forests(Inland Mountain West Symposium, 1985-08) Weaver, T.; Forcella, FWhitebark pine cone production was estimated for a 6 to 8 year period in each of 29 stands widespread in.the northern.Rocky Mountains. 1) One-time sampling was possible since the estimate was m2de by multiplying the number of branches perm by an estimate of annual cone production made from counts' of cone lets, mature cones, or cone scars on successively older annual increments of those branches. 2) Average cone production ranged from 0.3 to 3.6 cones·m^-2 ·yr^1 and from 22-270 seeds·m^-2·year^-1 . 3) Regression analysis was used to relate the variance observed to time and place. a) Year-to-year variation in the cone yield of branches, trees, and stands in a region appears to be both internally and externally controlled. Internal control is suggested by the fact that good cone years were usually preceded by poor cone years. While external control is indicated by significant correlations between growth and weather conditions, control is not dominated by the effect of any one factor or any particular developmental stage. b) Although cone production of the average branch varied significantly within 30 percent of the trees and within 48 percent of the stands observed, it did not vary significantly among stands. c) Regressions relating stand cone production to easily measured stand characteristics such as canopy cover, fallen cones, and/or stand size explain no more than 50 percent of the variance among stands.Item Bibliography of Montana vegetation description(1988) Burgeron, P.; Kratz, A.; Weaver, T.; Weidman, N.Listed in alphabetical order by author are 549 references to literature that describes the native vegetation of Montana. This updates the 1965 list of Habeck and Hartley. A keyword subject index is included.Item Biomass and productivity of the subalpine Pinus albicaulis — Vaccinium scoparium association in Montana, USA(1977-10) Forcella, F.; Weaver, T.Item Biomass of fifty conifer forests and nutrient exports associated with their harvest(1977) Weaver, T.; Forcella, F.Biomasses of climax Rocky Mountain forests studied ranged from less than 50 to more than 300 tons/ha. Total biomass was approximately 1.5 times the biomass of normally merchantable boles. When compared with conventional bole harvest, the nutrient exports associated with harvest of all aboveground parts in these stands would apparently be at least three times higher for nitrogen, six times higher for phosphorus, four times higher for potassium, and three times higher for calcium.Item Trampling Effects on Vegetation of the Trail Corridors of North Rocky Mountain Forests(1974-08) Dale, D.; Weaver, T.The management of trails should be based on knowledge of the effects of humans on them; most of the available information has been reviewed by Speight (1973), Stankey & Lime (1973), and Liddle (1975). Observations of existing trails suggest the following conclusions. (1) Vegetation cover is reduced by trampling and some plants are more resistant to trampling than others (Speight 1973; Liddle 1975; Dale & Weaver 1974; Davidson & Fox 1974). (2) Trail width increases linearly with increasing slope, wetness, roughness and the logarithm of the number of users (Bayfield 1973; Dale & Weaver 1974), but decreases linearly with the logarithm of the roughness of trailside vegetation and terrain (Bayfield 1973). Vegetation more than 2 m from the edge of a trail is often little effected (Dale & Weaver 1974). (3) Trail depths depend on compaction and erosion and therefore on climate, vegetation type, soil and substrate type, slope, and type of user (Helgath 1975; Dale & Weaver 1974). (4) Soil compaction is usually greater, i.e. bulk densities average 02-06 g cm-3 greater, in trampled areas than in untrampled areas. Several experimental studies .have shown the quantitative effects of wear on vegetation (Bell & Bliss 1973; Liddle 1975; Liddle & Greig-Smith 1975; Rogova 1976) but there has been no experimental comparison of the effects of different modes of trail travel. The experiments reported below compare the effects of hiker, motorcycle, and horse trampling on level and sloping sites in both a meadow and a forest with a dwarf shrub understorey.Item Ecological effects of weather modification: effect of late snow melt on Festuca idahoensis meadows(1974) Weaver, T.Diversity, cover and productivity of Festuca idahoensis meadows become progressively lower as one moves: (1) from deep-soil to shallow-soil sites, or (2) from sites that melt out in mid-May to sites that melt in late May or early June. Changes in species composition are also obvious on late melting sites. Changes associated with different melt dates are probably due to the shorter growing season of the late melting sites. Winter weather modification programs are expected to add snow, postpone melt, shorten the growing season and degrade these meadows in proportion to the amount of snow they add. Especially if the snow is deposited in drifts, the 10-15% increases in snowfall probably achievable will have small effects on the "target area" while returns to the "service area" might be considerable.Item Pinus albicaulis in Central Montana: Environment, Vegetation and Production(1974-07) Weaver, T.; Dale, D.Nineteen apparently climax, non-krumholz, whitebark pine (Pinus albicaulis) forests were sampled at 2490-2930 m in the Rocky Mountains of S-Central Montana. The understory of these forests is strongly dominated by Vaccinium scoparium (median cover 40% +). Mature stands (200 + years old), with trees 12 m high, had basal areas of 14-24 m2/ha and had merchantable volumes of 195 m3/ha. Whitebark stands usually occur on soils of igneous origin. The growing season in a typical stand has 3 wet months with over 80 mm of rain and 3 dry months with less than 50 mm of rain; average maximum temperatures in this period rose to 20 C while average minimum temperatures Jell below 0 C.