Theses and Dissertations at Montana State University (MSU)
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Item A comprehensive study on forest management and wildfire trends in dry western coniferous regions of the United States(Montana State University - Bozeman, College of Agriculture, 2024) Schonenberg, Richard Herman; Co-chairs, Graduate Committee: Anthony Hartshorn and William KleindlIn response to the growing concern over the escalating severity of wildfires in dry coniferous forests across the Western United States, this study aims to evaluate the effectiveness of Managed Fire Operations (MFO) in mitigating wildfire severity. By leveraging satellite-derived fire severity data, specifically the Difference Normalized Burn Ratio (dNBR), I conducted a comprehensive analysis comparing fire severity between forest lands with and without MFO, subsequently affected by wildfires. Employing a paired study design, I analyzed wildfire events from 1985 to 2021 within dry coniferous forests, limited to south-facing slopes with moderate terrain gradients, using fire perimeter data from the Monitoring Trends in Burn Severity (MTBS) program. Geospatial analysis identified areas where wildfire perimeters intersected with MFO-designated zones, enabling the delineation of new burn perimeters for each wildfire. The results revealed that regions subjected to MFO before wildfires experienced a statistically significant decrease in fire severity compared to areas without MFO (Wilcoxon signed-rank test, p-value < .01). Ecoregion stratification revealed notable variations, with the Northwestern Forested Mountains showing an estimated median fire severity difference nearly three times greater than the Temperate Sierras. Further stratification by time since MFO implementation displayed consistent, modest reductions in fire severity across two intervals (0-15 years and 15-40 years), with minimal variations between the temporal categories. These results highlight the effectiveness of MFO in mitigating wildfire severity and emphasize the importance of regional context and temporal factors in evaluating MFO efficacy in Western U.S. dry coniferous forests over the past four decades.Item Climate-fire-vegetation dynamics in the Greater Yellowstone Ecosystem: recent trends and future projections in a changing climate(Montana State University - Bozeman, College of Letters & Science, 2020) Emmett, Kristen Dawn; Co-chairs, Graduate Committee: Benjamin Poulter and David Roberts; Katherine M. Renwick and Benjamin Poulter were co-authors of the article, 'Disdentangling climate and disturbance effects on regional vegetation greening trends' in the journal 'Ecosystems' which is contained within this dissertation.; Katherine M. Renwick and Benjamin Poulter were co-authors of the article, 'Adapting a dynamic vegetation model for regional biomass, plant biogeography, and fire modeling in the western U.S.: evaluating LPJ-GUESSLMFIRECF' submitted to the journal 'Ecological modelling' which is contained within this dissertation.; Benjamin Poulter was a co-author of the article, 'Processed-based modeling approaches for climate-vegetation-fire feedbacks in the Greater Yellowstone Ecosystem' which is contained within this dissertation.Climate change threatens to change forested ecosystems and wildfire characteristics across the globe. For the Greater Yellowstone Ecosystem (GYE), under future warming temperatures, wildfire activity is expected to increase and the suitable habitat for many dominant tree species is expected to shrink. Previous studies predict large high severity fires to occur more frequently, potentially so frequent that forests are unable to grow old enough to produce seeds and self-regenerate. Studies of suitable climate spaces show that previously habitable areas may become too warm or dry to support common GYE trees. The first goal of this dissertation was to use vegetation images from satellites to detect recent changes in forest productivity in the GYE, and then determine the relative importance of recent climate and disturbance observations in explaining these changes. We found that areas with detected increases in plant growth, or 'greening' trends, were associated with forested areas regenerating after wildfire. Detected decreases in plant growth, or 'browning' trends, were associated with areas that had recently burned. Historically dry areas with recent increases in precipitation were associated with greening trends. Warming of 0-2 °C was associated with greening trends, while greater increases in temperature (>2 °C) were correlated with browning trends. The key take-away is although forests in the GYE are usually considered temperature limited, changes in precipitation may be more important than previously thought. The second goal of this dissertation was to adapt a global vegetation computer model for regional applications to simulate forests and wildfire dynamics, ultimately to run simulations under future climate conditions to predict how forest extent and composition may change. Life history characteristics and climate limitations were aquired for the dominant GYE plant types to dictate their establishment, growth, competition, and mortality in the new model. Before running future simulations, it is required to evaluate how well the model represents current conditions. Adding new equations that calculate the initiation, spread, and effects of crown fires was required to reproduce recent vegetation abundance, distribution of plant types, and fire activity in the GYE. Methods, expected results, and implications of running future simulations are described in Chapter 4.Item Effects of grazing after wildfire on soil health in eastern Montana(Montana State University - Bozeman, College of Agriculture, 2021) Hanson, Joshua Todd; Chairperson, Graduate Committee: Clayton B. Marlow; Clayton B. Marlow, Kurt O. Reinhart, Lance T. Vermeire and Sam A. Wyffels were co-authors of the article, 'Effects of grazing after wildfire on indicators of soil health in eastern Montana' submitted to the journal 'Fire ecology' which is contained within this thesis.Rangelands are resilient to grazing and fire. However, the resilience of rangelands may be degraded by livestock grazing too soon after wildfire. Due to the growing interest in soil health and its link to sustainable grazing, following a large wildfire (109,346 ha, Lodgepole complex in 2017) we tested the effect of grazing (grazed verses no grazing) on three indicators of soil health in ponderosa pine savvanas of the northern Great Plains. We measured indicators of soil hydrologic function (i.e., soil hydraulic conductivity), properties related to nutrient cycling (i.e., soil organic matter, plant available nutrients, pH), and soil structure (i.e., aggregate stability) in 2019 and 2020. Grazing occurred two out of three years following the fire. Most indicators of soil health were not appreciably affected by grazing post-fire. However, we detected a marginally significant negative effect of grazing on soil organic matter. Specifically, soil organic matter was 7% greater in ungrazed than grazed areas. No other grazing treatment effects were detected. Several soil health metrics varied between sampling years. Our results suggest that grazing(two out of the three years) following fire is unlikely to negatively affect many indicators of soil health of ponderosa pine savannas in the northern Great Plains. The increased organic matter observed by resting did not have an appreciable impact on the other soil health metrics. These findings suggest that soil health indicators are relatively resilient to grazing after wildfire and have implications for grazing policy post-fire.Item Evaluating grazing and defoliation effects on ponderosa pine grassland following the lodgepole complex wildfire(Montana State University - Bozeman, College of Agriculture, 2020) Williams, Amanda Rae; Chairperson, Graduate Committee: Clayton B. Marlow; Lance T. Vermeire, Richard C. Waterman and Clayton B. Marlow were co-authors of the article, 'Evaluating grazing effects on ponderosa pine grassland following the lodgepole complex wildfire' submitted to the journal 'Rangeland ecology and management' which is contained within this thesis.; Lance T. Vermeire, Richard C. Waterman, Clayton B. Marlow were co-authors of the article, 'Season of defoliation effects on ponderosa pine grassland following the lodgepole complex wildfire' submitted to the journal 'Rangeland ecology and management' which is contained within this thesis.Previous research indicated rangelands need rest from grazing after fire, while others show grazing the first year following fire has no negative effects on the plant community. This caused uncertainty around post-fire grazing management. In July 2017, the Lodgepole Complex fire burned ponderosa pine grasslands of the northern Great Plains, including areas burned in 2003 for fuels mitigation. We examined effects of post-fire grazing and season of defoliation. For the grazing study we wanted to determine 1) plant community response to grazing or rest the first growing season after fire in ponderosa pine grassland communities, and 2) whether prescribed fire alters plant community response to subsequent wildfire. For the season of defoliation study we wanted to determine 1) timing of defoliation effects on the plant community one growing season after fire and 2) whether defoliation effects are altered by prescribed fire preceding the fire. Eight exclosures (25 x 15 m) were built, 4 reburned sites and 4 wildfire sites. A non-grazed (15 x 10 m) section inside each exclosure was paired with a grazed section outside the exclosure. Plots (5 x 10 m) were mowed in the exclosure to 10 cm in June, July, or August, or not mowed during 2018. In 2019, biomass samples were clipped at peak production, with species composition and diversity measured by point-intercept transects. We observed a trend for reduced cool-season grasses (P =0.0675) and annual grasses (P =0.0071) if defoliated earlier; a trend for reduced forbs (P =0.0699) if defoliated later; and reduced total current-year biomass (P =0.0362) if defoliated. Functional group composition was not changed, but some individual species were shifted due to fire history. The grazing study only showed a trend for greater old dead biomass on non-grazed sites (P = 0.0600), higher composition of forbs on reburn sites (P = 0.0324), and a trend for a higher composition of Psoralidium tenuiflorum (Pursh) Rydb. on reburn sites (P = 0.0559). Results indicate mowing the first year following fire shifts the plant community, but the community is resistant to post-fire grazing. Prescribed fire 14 years before wildfire had small impacts on community composition.Item Understanding the effects of wildfire on the functional traits of plants and bees(Montana State University - Bozeman, College of Letters & Science, 2018) Durney, Janice Simone; Chairperson, Graduate Committee: Laura BurkleDiversity, often assessed by species richness, fosters ecosystem success, promoting ecosystem services, stability, and adaptation. Evaluations of functional trait composition are a better indicator of ecological process dynamics. Functional trait variation of species within a community (i.e., inter-specific variation) and of individuals within a species (i.e., intra-specific variation) may reflect adaptations and phenotypic variation contributing to the functional diversity of a community in the face of change. Wildfires have shifted from mixed-severity to frequent high-severity fires, due to fire suppression and climate change, modifying ecosystem function, trait selection pressure, and species sorting. Traits involved in plant-pollinator interactions can be used to understand the mechanisms underlying shifting interactions across communities and how post-wildfire environmental conditions affect community assembly, structure, and stability. We tested how productivity, time-since-burn, and wildfire severity influenced mean functional trait values and inter- and intra-specific functional trait variation of plants and bees known to interact in southwestern Montana, USA. Fieldwork was conducted from 2013-2017 in two locations that differed in productivity with similar fire histories of recent-mixed-severity, recent-high-severity, older-high-severity burns, and unburned areas. Functional traits involved in plant-bee interactions were selected and measured among plant and bee species observed across these various productivity, time-since-burn, and fire severity levels. We found that as productivity and time-since-burn increased, the mean functional trait values and inter- and intra-specific functional trait variation of plants and bees increased. In addition, productivity, time-since-burn, and fire severity affected the functional trait values and variation of plant species more than bee species. These results suggest that as productivity and time-since-burn increases so does trait diversity - promoting ecosystem function and stability. The increased effect of productivity and time-since-burn on plant functional traits compared to bee traits suggests the dispersal abilities of bees allow them to cope with the effects of fire, while plant species are more prone to productivity and time-since-burn habitat filtering and species sorting, potentially due to limited mobility. Our results support previous findings that shifting wildfire regimes from mixed to high-severity burns increases species sorting and limits trait variation after wildfire regardless of productivity but trait variation increases as time-since-burn and productivity increases.Item Plant-pollinator network assembly after wildfire(Montana State University - Bozeman, College of Letters & Science, 2018) Simanonok, Michael Peter; Chairperson, Graduate Committee: Laura BurklePlant-pollinator networks are threatened by anthropogenic influence due to habitat loss, changing fire regimes, climate change and other factors. Furthermore, we have little current knowledge for how species interactions and processes like pollination assemble and recover post-disturbance. Studying the mechanisms by which plant-pollinator interactions assemble in a post-disturbance landscape, particularly across gradients of disturbance intensity and successional time, would greatly help in building foundational ecological knowledge regarding the assembly of species interactions as well as provide specific information to aid conservation and management. Therefore, we investigated plant-pollinator network assembly after wildfire, between mixed- and high-severity burns and across time-since-burn, and we asked i) how do network structure and the network roles of persistent species vary ii) how does wildfire change the nutritional landscape of available floral pollen quality and how does that influence bumble bee foraging and nutrition, and iii) how do nesting and floral resources affected by wildfire influence wood-cavity-bee nesting success and richness? Our study design involved four wildfires from the Absaroka Mountains of southwest Montana, USA, which included a range of burn severities as well as a 1-25 year chronosequence of time-since-burn sampled primarily from 2014 to 2016. Bees were sampled via hand netting and nesting boxes alongside floral census transects and pollen sampling to assess metrics important to plant-pollinator network assembly, available floral pollen quality, bumble bee nutrition, and wood-cavity-nesting bee nesting success. The primary findings are that i) plant-pollinator network structure does not dramatically shift with burn severity or time-since-burn, nor do the network roles of persistent species, ii) available floral pollen quality and bumblebee nutrition are limited by high-severity burns, and iii) burn severity has little effect on the nesting success of wood-cavity-nesting bees. The conclusions that follow these results are mainly that i) evidence of constant structure and low variance of species' roles provides evidence for preferential attachment over opportunistic attachment in assembling plant-pollinator networks post-disturbance, ii) varied species composition between mixed- and high-severity burns may mean that bumble bees are nutritionally limited in high-severity burns, and iii) nesting resources do not appear to strongly limit nesting success or richness of wood-cavity-nesting bees.Item The influence of post-wildfire logging on forb and pollinator communities and forb reproductive sucess, Gallatin National Forest, Montana(Montana State University - Bozeman, College of Letters & Science, 2016) Heil, Laura Jean; Chairperson, Graduate Committee: Laura BurklePollinators are in decline worldwide, and these declines have implications for flowering plants and their reproduction, given that 80% of flowering plants depend on insects for pollination. One potential contributor to pollinator species' declines is shifts in disturbance regimes, such as increased severity and frequency. Wildfires are essential natural disturbances that are important drivers of forest biodiversity in the western U.S., and there is often pressure to respond to wildfire with management including post-wildfire logging. This management strategy involves the removal of dead trees for economic value immediately following wildfire. Thus, is expected that post-wildfire logging has additional impacts on forest communities compared to non-salvage logging, and that it impacts forb and pollinator communities. Several studies have examined the short-term responses of forb and pollinator communities to wildfire and non-salvage logging individually, and one study examined their combined effects. However, no studies have examined the long-term effects of post-wildfire logging, on forb and pollinator communities and on forb reproduction. My research addresses these gaps in knowledge and asks: 1) how do floral and bee communities respond to post-wildfire logging and how do their responses differ between two different-aged fires, and 2) how does post-wildfire logging influence forb reproduction and pollen limitation of reproduction in an older wildfire? In the more recent fire, floral and bee density and species richness were higher in logged than unlogged areas. By contrast, in the older fire, forb and bee communities were similar between logged and unlogged areas. Unexpectedly, we found large inter- and intra-annual variation in the effects of post-wildfire logging. Lastly, in the older fire, there were no effects of post-wildfire logging on forb reproduction, but plants were pollen limited in unlogged areas. This suggests that plants in unlogged areas are able to augment their reproductive output with supplemental pollen resources, but plants in logged areas cannot. Together, these results suggest that post-wildfire logging is beneficial for forbs and pollinators in the short-term, and these positive effects depend on time of growing season and sampling year. However, post-wildfire logging may be detrimental for forb reproduction in the long-term.Item The effects of fire and grazing in the northern mixed-grass prairie : implications from the Pautre wildfire(Montana State University - Bozeman, College of Agriculture, 2016) Gates, Emily Ann; Chairperson, Graduate Committee: Clayton B. Marlow; Lance T. Vermeire, Clayton B. Marlow and Richard C. Waterman were co-authors of the article, 'Reconsidering rest following fire: northern mixed-grass prairie is resilient to spring wildfire and resistant to moderate post-fire grazing' submitted to the journal 'Rangeland ecology and management' which is contained within this thesis.; Lance T. Vermeire, Clayton B. Marlow and Richard C. Waterman were co-authors of the article, 'Season of post-fire defoliation: effects on biomass, community composition and ground cover' submitted to the journal 'Rangeland ecology and management' which is contained within this thesis.; Lance T. Vermeire, Clayton B. Marlow and Richard C. Waterman were co-authors of the article, 'Forage fiber digestibility dynamics in the northern mixed-grass prairie following spring wildfire' submitted to the journal 'Rangeland ecology and management' which is contained within this thesis.Current federal recommendations pertaining to the management of post-fire grazing on rangelands interrupts historic disturbance regimes of the North American prairies by indicating that fire and grazing should be separated by at least two growing seasons. In contrast, some scholars suggest that North American prairie evolved under a tight linkage of fire and proximate post-fire grazing and should be well adapted to these combined disturbances. The Pautre wildfire of April 2013 provided an opportunity to test the effects of post-fire grazing in the northern mixed-grass prairie. One grazing allotment, burned in its entirety, and three burned and nonburned sites spanning a north-south gradient of the fire perimeter were selected as study locations. The effects of grazing versus rest, defoliation during the first spring, summer, or fall following the fire on burned and nonburned sites and the effects of fire on forage fiber digestibility were tested. Sites grazed during the first two growing seasons following the fire were found to recover similarly to sites rested during that same time. In addition, defoliation during any season following the fire produced no negative effects when compared to nondefoliation. Increases in forage fiber digestibility peaked shortly after fire and were short-lived, diminishing by the following year. These results lend support to the theory that fire and grazing were historically linked disturbances throughout the evolution of the North American prairies, indicating that the federal recommendation of rest is unnecessary in at least the northern mixed-grass prairie ecoregion. Historic, evolutionary patterns of disturbances, such as fire and grazing, may be useful in determining the most appropriate post-fire management regimes for specific ecoregions.Item Run-time optimization of a radiation driven crown fire model(Montana State University - Bozeman, College of Engineering, 1997) Call, Patrick TimothyItem Determinants of fire regime variability in lower elevation forests of the northern Greater Yellowstone Ecosystem(Montana State University - Bozeman, College of Agriculture, 2002) Littell, Jeremy Scott