Theses and Dissertations at Montana State University (MSU)
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Item Impacts of forest mortality on streamflow in whitebark pine forests within the greater Yellowstone ecosystem(Montana State University - Bozeman, College of Letters & Science, 2024) Rautu, Teodora Stefana; Co-chairs, Graduate Committee: Brian V. Smithers and Danielle E. M. UlrichIncreasing forest mortality across the western U.S. raises concerns about its impact on streamflow. The hydrologic role of whitebark pine (Pinus albicaulis Engelm.) is of particular interest given its ongoing decline and prevalence at the upper treeline where precipitation is highest. Understanding the link between disturbed whitebark pine forests and streamflow is essential for better informing water resource management. In Chapter One, I investigated streamflow changes in two Wyoming whitebark pine watersheds: Upper Wind River (53% area affected by beetle outbreak) and Buffalo Fork (53% area affected by beetle outbreak and fire). Streamflow significantly increased post-beetle for Upper Wind River but did not significantly change post-disturbance for Buffalo Fork, attributed to the fire's limited spatial extent and post- beetle effects potentially occurring in the pre-disturbance period. In Chapter Two, I integrated Leaf Area Index into a hydrologic model to reflect changing canopy conditions and assessed water balance variables that drove the observed changes in streamflow in Chapter One. I found that an increase in annual precipitation primarily led to the increase in observed streamflow more so than forest mortality, and snowpack and snowmelt were consistent predictors of streamflow metrics. My findings suggest monitoring snow dynamics for accurate real-time and future streamflow forecasting. In Chapter Three, I used streamflow field data and the same hydrologic model to assess the impact of increasing tree mortality on streamflow within a whitebark pine- dominated watershed in Big Sky, Montana. After simulating mortality levels ranging from 0-90% for one year, tree mortality did not substantially impact streamflow until the 90% mortality level where annual flow and late summer flow substantially increased. Considering that mortality levels between 25-50% are more representative of whitebark pine mortality in one year, the lack of substantial impacts on snowpack and streamflow at the 25-50% mortality levels challenges the traditional assumption that whitebark pine mortality would lead to reduced snowpack and reduced late summer flow in open watersheds with 30% forest cover. Future studies should assess the multi-decade impacts of whitebark pine mortality on hydrologic processes and consider species differences in evapotranspiration as other subalpine species replace whitebark pine.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 Linking plant and soil nutrient dynamics in temperate and tropical montane forests(Montana State University - Bozeman, College of Letters & Science, 2018) Qubain, Claire Anne; Chairperson, Graduate Committee: David Roberts; Jia Hu (co-chair); Yuriko Yano and Jia Hu were co-authors of the article, 'Linking nitrogen allocation in douglas-fir to soil nitrogen availability in a western montane conifer forest' submitted to the journal 'Oecologia' which is contained within this thesis.; Diego Riveros-Iregui and Jia Hu were co-authors of the article, 'Climate and invasion drive soil nutrient dynamics in tropical montane forests of the Galapagos archipelago' submitted to the journal 'Ecology' which is contained within this thesis.I built on our fundamental understanding of ecosystem function by examining how climate variability influences feedbacks between plant processes and soil nutrient dynamics. At Lubrecht Experimental Forest, I examined how variability in snow depth, precipitation, and soil moisture influenced seasonal nitrogen allocation in Douglas-fir. I then examined if N cycling within Douglas-fir synchronized with patterns of N availability in the soil. In this case, N availability in the soil influenced plant nutrient dynamics. On the other hand, on San Cristobal Island in the Galapagos Archipelago, plants fed back and influenced soil nutrient dynamics. Changes in precipitation, soil moisture, and temperature strongly controlled nutrient concentrations in the soil, and to a lesser degree, plant community type determined nutrient concentrations, especially N concentrations, in the soil.Item Bird response to landscape pattern and disturbance across productivity gradients in forests of the Pacific Northwest(Montana State University - Bozeman, College of Letters & Science, 2007) McWethy, David Burch; Chairperson, Graduate Committee: Andrew HansenManaging forest lands for biodiversity is a common goal in the public and private forests of the Pacific Northwest and is typically achieved through harvests that result in an array of vegetation structural conditions that provide suitable habitat for a number of species. The assumption is made that the causative factors of biodiversity do not vary geographically and that silviculture, as a management tool, can be applied similarly across different biophysical locales. The primary aim of this research is to better understand how species respond to both local and landscape-scale forest structural conditions in landscapes with different levels of productivity (e.g. gross primary productivity). We hypothesized that the influence of landscape effects on bird richness, abundance and community organization would be more pronounced in highly productive environments. We also hypothesized that species response to disturbance would differ across gradients in ecosystem productivity. We predicted that bird diversity would increase with increasing disturbance extent where favorable climatic conditions result in high levels of competitive exclusion. Alternatively, we predicted that bird diversity would decrease with increasing disturbance extent when factors other than competition limit or regulate bird species diversity.Item Biodiversity potential in the Pacific and Inland Northwest : the relative importance of forest structure and available energy in driving species diversity(Montana State University - Bozeman, College of Letters & Science, 2007) Verschuyl, Jacob Pieter; Chairperson, Graduate Committee: Andrew J. HansenCurrently, the most common strategy of forest biodiversity managers in the Pacific and Inland Northwest (PINW) is to maintain structural complexity within forest stands and create the full range of seral stages across the landscape. Recent advances in ecological theory reveal that biodiversity at regional to continental scales is strongly influenced by available energy (i.e. factors influencing vegetative growth such as precipitation, temperature, radiation, soil fertility). We hypothesized bird species richness (BSR) exhibits a positive or unimodal relationship with energy across landscapes and the relationship between energy and BSR within a landscape is positive in energy limited landscapes and flat or decreasing in energy rich landscapes. Additionally, we hypothesized that structural complexity explains a lower percentage of the variation in BSR in energy limited environments and higher percentage in energy rich environments and that the slope of the relationship between structural complexity and BSR is greatest in energy rich environments.Item Classification of the grasslands, shrublands, woodlands, forests and alpine vegetation associations of the Custer National Forest portion of the Beartooth Mountains in Southcentral Montana(Montana State University - Bozeman, College of Letters & Science, 2012) Williams, Kristin Louise; Chairperson, Graduate Committee: David Roberts; Dave W. Roberts was a co-author of the article, 'Classification of shrubland associations of the Beartooth Mountains study area and comparison to existing grassland and shrubland habitat type classifications' in the journal 'Western North American naturalist' which is contained within this thesis.; Dave W. Roberts was a co-author of the article, 'Classification of woodland and forested vegetation associations of the Beartooth Mountains study area and comparison with existing woodland and forested habitat type classifications' in the journal 'Western North American naturalist' which is contained within this thesis.; Dave W. Roberts was a co-author of the article, 'Classification of the alpine vegetation associations of the Beartooth Mountains study area' in the journal 'Western North American naturalist' which is contained within this thesis.The purpose of this thesis was to classify and describe low-elevation grassland and shrubland vegetation, mid-elevation woodland and forested vegetation, and high elevation alpine vegetation associations of the Beartooth Mountains study area and to compare newly derived associations with existing habitat type and community type classifications of ecologically relevant environments in Montana, Wyoming and Idaho. Five grassland/shrubland associations, twelve woodland/forested associations and thirteen alpine associations were classified and described for the Beartooth Mountains study area. Prior to this thesis, no comprehensive vegetation association classification of the Beartooth Mountains, the highest, largest and easternmost alpine region in Montana, has been conducted.Item Epiphytic lichens, nitrogen deposition and climate in the US northern Rocky Mountain states(Montana State University - Bozeman, College of Letters & Science, 2012) Grenon, Jill Ann; Chairperson, Graduate Committee: David Roberts; David W. Roberts, Mark E. Fenn, Linda H. Geiser and Sarah Jovan were co-authors of the article, 'Using epiphytic lichens to monitor nitrogen deposition near natural gas drilling operations in the Wind River range, WY' in the journal 'Journal of air & waste management association' which is contained within this thesis.; David W. Roberts and Linda H. Geiser were co-authors of the article, 'Epiphytic lichen indication of nitrogen deposition and climate conditions in the Northern Rocky Mountains' in the journal 'Environmental pollution' which is contained within this thesis.; David W. Roberts and Linda H. Geiser were co-authors of the article, 'Climate patterns as indicated by epiphytic lichen communities: a forest inventory and analysis indicator model for the NW interior mountains, USA' in the journal 'Government technical report' which is contained within this thesis.Forested ecosystems in the NW Interior Mountains (NWIM) of the United States are jeopardized by degrading air quality and changes in climate regimes. Monitoring and tracking changes in air quality and climate through instrumentation alone can be an expensive and challenging task. Biomonitors offer a cost-effective way to maximize monitoring resolution. This thesis explored the utility of lichens as biomonitors across three sections of the NWIM. First, in the Wind River Range, WY, nitrogen concentrations (%N) in lichen thalli were calibrated with measurements of canopy throughfall N deposition. A strong correlation verified % N as a useful metric to estimate N deposition. Nitrogen deposition in the Boulder drainage, closest in proximity to large natural gas drilling operations, was clearly elevated above estimated background conditions and measurements from other drainages. Degraded lichen communities were observed at deposition levels of 4.0 kg N ha -¹year -¹. The second study used lichen community composition, elemental analysis, and lichen functional groups to analyze the importance of nitrogen deposition and climate on lichen communities along the northern Rocky Mountains. Temperature and relative humidity were the most important climatic influences on community structure. A nitrogen pollution signal was independent of climate. The relationship between % N in lichen thalli and throughfall N (study 1) was used to estimate N deposition along the northern Rocky Mountains. Eutroph (N-tolerant) and oligotroph (N-sensitive) functional group indices were correlated with both N deposition and climate. Elevated N deposition (twice background conditions) was most notable around Bozeman, MT and Pinedale, WY. The final study stratified plots across the NWIM by latitude and longitude and found precipitation, dew point, and temperature were important variables to lichen community composition. Eutroph and oligotroph distributions were partially accounted for by climate; unfortunately no N data were available for comparison to lichen communities. The models created can be utilized for monitoring changes in lichen communities over time and to predict N deposition and climate conditions for new plots. Additionally, these models can be used to address management and conservation questions related to individual lichen species, lichen communities, forest health, air quality, and climate conditions.