Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Seasonal water relations in native and reconstructed mine soils : implications for ponderosa pine establishment(Montana State University - Bozeman, College of Agriculture, 1998) Jennings, Karin MarieItem Toadflax, fire, Mecinus janthinus, and compensatory growth(Montana State University - Bozeman, College of Agriculture, 2005) Anthony, Antoinette; Chairperson, Graduate Committee: Theodore Weaver.Dalmatian toadflax is a noxious weed of the western United States. In western Montana it invades in the foothills zone where bunchgrasses (Agropyron spicatum and Festuca idahoensis) meet low forests (Pinus ponderosa and Pseudosuga menziesii). Our results show that wildfire strengthens toadflax, probably at the expense of native grasses. The stem boring weevil, Mecinus janthinus, is being tested as the most likely biocontrol agent for the weed. On our toadflax infested sites in the Agropyron spicatum/Pinus ponderosa zone Mecinus established, survived, and spread slowly (2-4m/yr) for two years following introduction. At the low initial densities Mecinus induced compensatory growth in toadflax i.e. stem density, plant height, branch number, and seed capsule number all increased. In a garden experiment, we exposed plants to Mecinus at increasingly higher densities (0-32 insects per plant) to measure the effect of a higher attack rate. With exposure rates of 2-4 insects per plant compensatory growth occurred. With exposure rates greater than 8 insects per plant total biomass and especially flower biomasses were reduced. If Mecinus densities in the field exceed eight weevils per plant this may indicate eventual exhaustion and decline of the weed.Item Soil and plant response to slash pile burning in a ponderosa pine forest(Montana State University - Bozeman, College of Agriculture, 2009) Meyer, Natalie Jo; Chairperson, Graduate Committee: Catherine A. Zabinski; Thomas DeLuca (co-chair)Slash pile burning is the most common method of forest residue disposal following ponderosa pine restoration harvests, which are intended to reduce the risk of catastrophic fire and restore the historical structure and function of forests in western Montana. The impact of high-intensity, long-duration fire (pile burning) on soil processes and plant community dynamics is not well understood. The objectives of this study were: (1) to characterize the influence of slash pile burning on soil nutrient availability, soil microbial activity, and arbuscular mycorrhizal (AM) infection; (2) to compare seeding and soil amendment effects on burn scars. In May 2006, slash piles were burned in a ponderosa pine stand near Florence, Montana and 45 scars were sampled. Soil samples were collected from three locations in each slash pile to a depth of 10 cm and characterized for available soil NH 4 + -N, NO 3 - -N, potentially mineralizable nitrogen (PMN), and total C and N, water-soluble PO 4 ³- -P, microbial biomass, and mycorrhizal inoculum potential (MIP). In the burned center, soil NH 4 + -N was greatest one month post-burn and remained elevated one year later. There was no observable increase in NO 3 - -N until one year post-burn. Soluble PO 4 ³- -P was not impacted by burning. Microbial biomass was reduced by burning and did not recover one year later. Pile burning greatly reduced MIP. In October 2006, fire scars were either seeded with native graminoids or left non-seeded, divided into subplots, and assigned to one of five treatments: control, addition of local organic matter, scarification, scarification and organic matter addition, or scarification and commercial compost addition. Soils were monitored for the previously measured soil parameters and resin-sorbed inorganic N. Scarification with organic matter amendment and scarification with compost amendment both ameliorated soil properties. Seeding most effectively increased plant cover and suppressed non-native invasive species, while scarification or scarification with organic matter amendment further improved early plant establishment. Collectively, these data help characterize the impacts of slash pile burning as a management technique in ponderosa pine forests and illustrate potential treatments for restoring burn pile scars.