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Spatial analysis of the recovery of submerged aquatic vegetation in the Hudson river estuary following the 2011-2012 hurricane seasons
(Montana State University - Bozeman, College of Agriculture, 2019) Carroll, Sean Michael; Chairperson, Graduate Committee: Scott Powell
Submerged aquatic vegetation (SAV) is a critical habitat found in estuarine ecosystems throughout the world. SAV performs a multitude of ecosystem functions ranging from water quality improvement to habitat for macroinvertebrates and juvenile fish, and acts as a significant contributor to dissolved oxygen throughout the estuarine system. In the Hudson River Estuary (HRE), native SAV beds have been greatly reduced or altered by threats such as sedimentation, water quality issues, and the spread of invasive aquatic plants, as well as by disturbance from natural events such as large-scale storms. In 2011 and 2012, three hurricanes made landfall in the northeastern United States, having a tremendous impact on the Hudson River and the Hudson Valley region as a whole. SAV in the estuary was impacted by both storm surge as well as significant sediment deposition from the river's tributaries. However, in the wake of these events, there is uncertainty about the spatial patterns of SAV loss and recovery, and how these patterns are affected by the hydrology and physical characteristics of the river. Therefore, my study seeks to address this knowledge gap by investigating the impacts of these storms on SAV spatial patterns and the influence of SAV proximity to shoreline, tidal wetlands, and persistent "colony" SAV beds. I investigated these effects by analyzing overall (whole system) SAV recovery, the spatial patterns of recovery, and the correlation of recovery to prior SAV coverage and proximity to these features. Analysis was done using three years of remotely-sensed SAV GIS data, and was done at three different spatial scales. SAV coverages were determined at each scale for all three years and areal-change and percentage-change were calculated. Distance to the three aforementioned features was calculated for the fine-scale analysis. The results suggest that there was significant SAV loss river-wide between 2007 and 2014, followed by significant recovery between 2014 and 2016. Loss between 2007 and 2014 was greatest in the most upstream approximately 100 km of the river, likely a result of proximity to the Mohawk River, a major tributary and large sediment source during the storms. SAV recovery showed a similar pattern, occurring most in these upstream reaches. Distance from shoreline, tidal wetlands, and persistent SAV beds had varying impacts on SAV loss and recovery. The findings of this study help to elucidate both the potential impacts on the magnitude and patterns of vegetation loss following a large storm event and subsequent sediment flux, as well as the recovery potential of this vegetation during 'normal' years. Such information can help inform future biological studies of the HRE and watershed management decision-making.
Soil restoration and invasive plants at the Block P Mill and tailings site, Montana
(Montana State University - Bozeman, College of Agriculture, 2019) Massey, John Gant; Chairperson, Graduate Committee: Scott Powell
My case study considers the Block P Mill and Tailings Site (also, Block P or the Site), a derelict lead and zinc production facility in the Little Belt Mountains of Montana. Fifteen years after environmental restoration activities concluded at this heavily contaminated site, I analyzed whether the canopy cover of plant species correlates with soil pH conditions. Specifically, I investigated whether addressing acidic conditions during mine-site restoration encouraged the presence of oxeye daisy (Leucanthemum vulgare), a non-native invasive plant species. Fieldwork in June 2019 included collection of soil pH and vegetation canopy cover data from 36 quadrats (6 m x 6 m) arrayed across this 6.6-ha restoration site. A Canonical Correspondence Analysis (CCA) of these data shows no statistically significant relationship between soil pH and overall plant species' canopy cover values. Further, linear regression analysis shows no statistically significant relationship between soil pH and the canopy cover of oxeye daisy. Therefore, it is unlikely that differences in the soil pH across the Site unevenly affect the canopy cover of plant species or unduly encourages the presence of oxeye daisy. These results are a reminder, however, that if restoration returns fertility to a previously barren and inhospitable site, the presence of novel assemblages of non-native and native plant species also may be generally encouraged, including invasive species such as oxeye daisy. I therefore conclude that the treatment of invasive plants at restoration sites like the Block P are a required managerial choice, not a philosophical imperative.
Understanding the biology, ecology, and integrated managment of Ventenata dubia
(Montana State University - Bozeman, College of Agriculture, 2019) Harvey, Audrey June; Chairperson, Graduate Committee: Jane M. Mangold; Lisa Rew, Timothy Prather and Jane Mangold were co-authors of the article, 'The effects of elevated temperature and CO 2 concentration on seedling growth of Ventenata dubia and Bromus tectorum' submitted to the journal 'Western North American naturalist' which is contained within this thesis.; Lisa Rew, Timothy Prather and Jane Mangold were co-authors of the article, 'Indaziflam provided up to three-years of control for Ventenata dubia in southwestern Montana' submitted to the journal 'Invasive plant science and management' which is contained within this thesis.; Stacy Davis, Lisa Rew, Timothy Prather and Jane Mangold were co-authors of the article, 'Effect of seeding date of Pseudoroegneria spicata (bluebunch wheatgrass) on establishment and subsequent ability to resist invasion by Bromus tectorum (cheatgrass)' submitted to the journal 'Ecological restoration' which is contained within this thesis.
Ventenata dubia (Leers) Coss., common name ventenata or African wire grass, is a non-native winter annual grass of increasing concern in western Montana. In North American, V. dubia appeared in the early 1950s; since then it has successfully established in the northeastern and northwestern United States. It is known to invade areas previously inhabited by Bromus tectorum (cheatgrass) and Taeniatherum caput-medusae (medusahead). In the Intermountain Pacific Northwest, V. dubia has caused substantial ecological and economic impacts in perennial grass habitats. Varying disturbance regimes contribute to its rapid expansion over the last decade. Impending climate change threats have the potential to exacerbate the spread of this invasive species. Three independent studies were conducted to explore the biology, ecology, and integrated management of V. dubia populations in Montana to alleviate impacts by this species and other invasive annual grasses. A growth chamber study tested the effects of elevated carbon dioxide and temperature on seedling growth of V. dubia in response to climate change and in competition with B. tectorum. This competition replacement study indicated that at elevated climate conditions V. dubia and B. tectorum grow smaller and competition with V.dubia has the potential to decrease B. tectorum growth. A field-based herbicide efficacy trial utilizing the active ingredient indaziflam compared it to other commonly used herbicides to determine long-term control of V. dubia and potential plant community changes at 8, 11, 20, and 23 months after treatment. Foliar cover, species richness, and functional group biomass were collected. Findings indicated indaziflam can control V. dubia up to three years with positive implications for plant community dynamics. A revegetation study was used to determine the optimum seeding time for perennial grass species, Pseudoroegneria spicata, and the effects seeding time can have with competition dynamics with B. tectorum. A randomized complete block design was established and P. spicata grown for one season prior to Bromus tectorum seeding. After the second growing season, tillers and biomass were collected for both species. Findings indicated priority effects can occur with fall and early spring seeding of P. spicata, with implications for suppression of B. tectorum at earlier seeding dates.
Overcoming the challenges of tamarix management with Diorhabda carinulata through the identification and application of semiochemicals
(Montana State University - Bozeman, College of Agriculture, 2018) Gaffke, Alexander Michael; Chairperson, Graduate Committee: David K. Weaver; Sharlene E. Sing, Tom L. Dudley, Daniel W. Bean, Justin A. Russak, Agenor Mafra-Neto, Paul A. Grieco, Robert K. D. Peterson and David K. Weaver were co-authors of the article, 'Semiochemicals to enhance herbivory by Diorhabda carinulata aggregations in saltcedar (Tamarix spp.) infestations' in the journal 'Pest management science' which is contained within this thesis.; Sharlene E. Sing, Tom L. Dudley, Daniel W. Bean, Justin A. Russak, Agenor Mafra-Neto, Robert K. D. Peterson and David K. Weaver were co-authors of the article, 'Field demonstration of a semiochemical treatment that enhances Diorhabda carinulata biological control of Tamarix spp.' submitted to the journal 'BioControl' which is contained within this thesis.; Sharlene E. Sing, Tom L. Dudley, Daniel W. Bean, Justin A. Russak, Agenor Mafra-Neto, Robert K. D. Peterson and David K. Weaver were co-authors of the article, 'Allee effects and aggregation pheromones: new releases of Diorhabda carinulata remain longer in the presence of pheromone formulations' submitted to the journal 'Biological Invasion' which is contained within this thesis.; Sharlene E. Sing, Jocelyn Millar, Tom L. Dudley, Daniel W. Bean, Robert K. D. Peterson and David K. Weaver were co-authors of the article, 'Behavioral responses of Diorhabda carinulata adults to repellent compounds isolated and identified in volatiles collected from conspecific larvae' submitted to the journal 'Journal of chemical ecology' which is contained within this thesis.
The northern tamarisk beetle, Diorhabda carinulata (Desbrochers), is an approved and established classical biological control agent for saltcedars (Tamarix spp.). Adequate control of Tamarix has not yet been achieved in certain areas where D. carinulata has been released. Retaining beetle populations on sites where it has been released is problematic, and accurately monitoring D. carinulata populations to determine successful establishment is difficult. Negative, indirect impacts have also resulted from the agent's establishment outside targeted treatment areas in the southwestern United States. Manipulation of D. carinulata spatial distribution with semiochemicals could potentially resolve or ameliorate these and other operational issues. Lures utilizing a specialized wax based matrix for the controlled release of semiochemicals were impregnated with a previously identified pheromone and/or behaviorally active host plant volatiles known to stimulate aggregation in D. carinulata. Emission of these compounds from the matrix was characterized using a push-pull volatile collection system, and quantified using gas chromatography-mass spectrometry. Observed release rates confirm that semiochemicals lures formulated with this matrix are a viable option for facilitating aggregation of D. carinulata under field conditions. The results of field-based assays indicate saltcedars treated with this semiochemical delivery system attracted and retained higher densities of D. carinulata than Tamarix that received a control (semiochemical free) lure. Higher densities of both adult and larval D. carinulata were recorded on treated plants. Semiochemically treated Tamarix plants also exhibited more damage, resulting in a greater decrease in canopy volume than control trees. The attraction and retention of D. carinulata to these species-specific semiochemicals on treated Tamarix plants also arrested the dispersal of newly released individuals, resulting in greater population growth. Repellent semiochemicals were also investigated for their potential to manipulate spatial distributions of D. carinulata in the field and behavioral assays conducted with reproductive adults demonstrated the ability of larval produced compounds to repel conspecific adults. These results indicate that semiochemical-impregnated media could be useful for detecting, retaining, and directing populations of D. carinulata. The use of semiochemicals could be used to potentiate low density populations, increase monitoring efficacy, retain adults on release sites, and repel D. carinulata from sensitive habitat.
Restoration of spotted knapweed infested grasslands in Glacier National Park
(Montana State University - Bozeman, College of Agriculture, 2003) Stringer, Lewis Tipton; Chairperson, Graduate Committee: Catherine A. Zabinski
There is an immediate and on-going need in Glacier National Park (GNP), and other public and private lands, to determine effective methods to re-establish and sustain native plant populations following control treatments of Centaurea maculosa. My research was developed in response to GNP concerns regarding annual herbicide treatment of C. maculosa invaded sites. The aim of this study was to determine if herbicide applications, site preparation and revegetation methods would increase the density and percent cover of native species, while reducing spotted knapweed at two sites in and near Glacier National Park. A priori contrast analysis was used to determine differences in treatment effects. The results of my experiment show that spot spray herbicide application reduced C. maculosa cover without significantly reducing existing native forbs. However, a repeat-herbicide application increased exotic graminoid cover. Tillage reduced the density of C. maculosa seedlings, but resulted in an increase in C. maculosa percent cover, and an overall decline in native forbs. Revegetation methods had limited success at increasing native species, and reducing C. maculosa. The only effect was at Swift Current, where the percent cover of native forbs was significantly higher with the planting treatment, and most pronounced in plots with repeat-herbicide application. Additionally, we measured the composition and density of the seed bank in C. maculosa dominated sites using the seedling emergence method. C. maculosa density was 3,900 and 6,714 seeds / m 2 at the two sites, which was 2 and 3 times higher than the sum of all other species. Seed bank composition and density needs to be considered in efforts to restore C. maculosa infested areas.
Disturbance and site characteristics relate to cheatgrass (Bromus tectorum) abundance on ranches in Montana foothills ecosystems
(Montana State University - Bozeman, College of Agriculture, 2016) Ozeran, Rebecca Kathleen; Chairperson, Graduate Committee: Craig Carr
Cheatgrass (Bromus tectorum L.), also known as downy brome, is an invasive, exotic annual grass found throughout North America. Cheatgrass has been extensively studied in the Great Basin region of North America, where the majority of precipitation comes in winter and early spring, and the vegetation consists primarily of cool-season species. However, little research has been done in northern foothills grasslands in and near Montana, where most precipitation comes in spring and summer, supporting a mixture of cool- and warm-season plant species. Climate and vegetation differ between the northern foothills grasslands and the Great Basin, so the ecological impacts of cheatgrass in the northern foothills grasslands are unknown. In order to better understand cheatgrass ecology in this region, we assessed cheatgrass abundance in foothills ecosystems in Montana. Fifteen study plots were established at each of two ranches in Montana, both of which are owned and operated by the Montana Agricultural Experiment Station: Thackeray Ranch, southeast of Havre, Montana, and Red Bluff Ranch, east of Norris, Montana. At these plots we examined relationships among cheatgrass abundance, biotic and abiotic site characteristics (e.g. species diversity, soil depth), and disturbance indicators (e.g. livestock fecal counts) in 2014 and 2015. Large generalized linear mixed-effects regression models for each ranch were reduced to simpler models by comparing the Aikake's Information Criterion (AIC) for each fitted model, and selecting for lower AIC to best describe cheatgrass abundance. Multimodel inference based on the best models for each ranch identified important variables to predict cheatgrass abundance. Disturbance and site characteristics such as aspect and soil texture are important predictors that land managers in the northern foothills grasslands could monitor to estimate the risk of cheatgrass invasion or dominance on the landscapes they manage.
Drivers, impacts, and feedbacks of global Pinus contorta (Lodgepole pine) invasions
(Montana State University - Bozeman, College of Agriculture, 2016) Taylor, Kimberley Terrill; Chairperson, Graduate Committee: Bruce D. Maxwell; Bruce D. Maxwell, Anibal Pauchard, Martin Nunez, Duane A. Peltzer, Andre Terwei and Lisa J. Rew were co-authors of the article, 'Drivers of plant invasion vary globally: evidence from pine invasions within six ecoregions' in the journal 'Global ecology and biogeography' which is contained within this thesis.; Bruce D. Maxwell, Anibal Pauchard, Martin Nunez and Lisa J. Rew were co-authors of the article, 'Native versus nonnative invasions: similarities and differences in the biodiversity impacts of Pinus contorta in introduced and native ranges' in the journal 'Diversity and distributions' which is contained within this thesis.; Bruce D. Maxwell, David B. McWethy, Cathy Whitlock, Anibal Pauchard, Martin Nunez were co-authors of the article, 'Positive feedback between Pinus contorta invasion and fire likely above an invasion density threshold' submitted to the journal 'Ecology' which is contained within this thesis.; Bruce D. Maxwell, Paul Caplat were co-authors of the article, 'Simulation model suggests that fire promotes lodgepole pine (Pinus contorta) invasion in Patagonia' submitted to the journal 'Biological invasions' which is contained within this thesis.
Pine species (genus Pinus) have been introduced across the Southern Hemisphere for forestry and several species have invaded surrounding ecosystems. Pine introduction across biogeographic regions sets up an ideal natural experiment to test underlying theories and assumptions of invasion biology. We studied the factors determining patterns of Pinus contorta invasion across nine sites in both the native and introduced ranges to understand how the invasion drivers change across sites and invasion stages. We found that propagule pressure is the most important factor in explaining invasion density in young invasions, but that biotic factors play an important role at later invasion stages. Additionally, we found higher invasion densities in the introduced than native range which may be explained by faster growth and earlier and more prolific reproduction in the introduced range. We examined the impacts of P. contorta invasions on plant biodiversity across sites and found that species richness and native plant cover decline with increasing P. contorta cover across sites in both the native and introduced range. There were more significant changes in species composition and individual species cover at grassland and shrubland sites in the introduced range than in the native range or a native forest site in the introduced range. Finally, there is concern that invasive pines, which are fire adapted, will alter fire regimes in a way that promotes a new fire-prone state further increasing their success over native plants. We examined the potential for P. contorta to form a positive feedback with fire by quantifying fuel loads and fire effects across an invasive gradient. We also examined P. contorta and native plant recovery following fire across an invasion density gradient. We found that fuel loads and simulated soil heating increased with older P. contorta invasions. Following fire, P. contorta dominated communities only when the pre-fire density was high. Therefore, we expect that a positive feedback between P. contorta invasion and fire will form only above an invasion threshold. Our invasion-fire simulation model suggested that fire in older invasions will increase invasion rates, but that fires in young invasions will not affect the invasion rate.
Occurrence and characterization of dicambre resistant Kochia (Kochia scoparia) in Montana
(Montana State University - Bozeman, College of Agriculture, 1998) Hackett, Josette Lynn
Investigating the potential of using R* theory to manage nonindigenous plant invasions
(Montana State University - Bozeman, College of Agriculture, 2004) Mangold, Jane Marie; Chairperson, Graduate Committee: Roger L. Sheley.
R* theory has been proposed as a mechanism for plant community dynamics, but the theory is poorly tested and has not been developed into a principle for management. This theory states that the outcome of succession is based on the ability of a plant to sequester a limiting resource when it is below the uptake level of neighboring species. ' R* is the resource level a species requires to persist in an environment, and the species with the lowest R* dominates over time. Knowledge of the R*s for species within a plant community could lead to effective weed management with predictive capabilities. The overall objective of this research was to explore R* theory’s potential for managing nonindigenous plant invasions on western rangeland. Specific objectives included: 1) determining the most influential limiting resource for a western rangeland plant community, 2) determining R*s for two native species and a nonindigenous invader, 3) predicting the outcome of succession based upon species’ R*, and 4) altering resource availability to favor desirable species based upon their R*. Three studies were conducted beginning in 2000. For Study 1, availability of essential plant resources were altered and the plant community was sampled for a biomass increase. Results of Study 1 suggested nitrogen was the major limiting resource for the dominant functional group. Study 2 was a greenhouse study that attempted to quantify the R* for nitrogen for three species. The R* for annual sunflower was 0.6 ppm NO3-N; the R* for bluebunch wheatgrass was less than 0.6 ppm NO3-N; and spotted knapweed’s R* was between 0.4 and 0.6 ppm NO3-N. Two- and three-species mixtures suggested estimated R*s accurately predicted the outcome of competition between natives, but not with natives and spotted knapweed. Study 3 tested succession dynamics under natural and nitrogen-manipulated conditions. Soil nitrogen was altered by nitrogen and sucrose additions. Annual sunflower did not persist. Spotted knapweed biomass increased with nitrogen addition but did not decrease with carbon addition, even though soil NO3-N was below its R*. Bluebunch wheatgrass appeared unaffected by nitrogen manipulation, but soil NO3-N concentration was not decreased below its R*.
Belowground mechanisms that affect nutrient uptake and response to herbivory of Centaurea maculosa and native bunchgrasses
(Montana State University - Bozeman, College of Agriculture, 2003) Zimmerley, Sara Theresa

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