Browsing by Author "Smith, Melinda, committee member"
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Item Open Access A comparative analysis of wetland and riparian vegetation on Bureau of Land Management land in the western US(Colorado State University. Libraries, 2023) Binck, Elin, author; Sueltenfuss, Jeremy, advisor; Reynolds, Lindsay, committee member; Smith, Melinda, committee member; Havrilla, Caroline, committee memberIn 2011, the BLM deployed its first of three Assessment, Inventory, and Monitoring (AIM) programs as a large-scale, standardized ecological monitoring effort across the agency's land. The first two programs, known as Terrestrial AIM and Lotic AIM, were designed to sample all terrestrial and river ecosystems throughout the landscape. In 2019, the agency piloted its third AIM program, specifically targeting riparian areas and wetlands. This study addressed two main questions: 1) How do wetland and riparian areas sampled with the Terrestrial AIM program compare to those sampled with the Riparian and Wetland (R&W) AIM program, and 2) What are the drivers of plant community composition of the wetlands and riparian areas sampled on BLM land? I developed a set of criteria to identify sites sampled with Terrestrial AIM that had characteristics of wetlands or riparian areas. I then compared vegetation cover, floristic quality metrics, and species composition using nonmetric multidimensional scaling (NMDS) to those sites sampled with R&W AIM. R&W AIM sites had much greater foliar cover, hydrophytic species cover, and perennial cover, but Terrestrial sites had slightly higher floristic metric values. I similarly analyzed the R&W sites on their own, incorporating wetland-specific data that is collected with the new program. I found that sites that met the criteria to be classified as wetlands in the Terrestrial data were a distinct population from the sites sampled with R&W AIM. The main drivers of plant community composition among sites sampled with R&W AIM were elevation and the distribution of surface water, but impacts of grazing were also apparent. All sites assessed by both AIM programs had floristic quality metrics characteristic of highly impacted wetland systems. This study indicates the value of the new R&W AIM program for its ability to perform wetland-specific ecological monitoring, provide valuable data on the health of wetlands, and provide baseline condition that can help guide land management practices into the future.Item Open Access A prickly puzzle: phylogeny and evolution of the Carduus-Cirsium group (Cardueae: Compositae), and untangling the taxonomy of Cirsium in North America(Colorado State University. Libraries, 2020) Ackerfield, Jennifer R., author; Simmons, Mark, advisor; Kondratieff, Boris, committee member; Smith, Melinda, committee member; Steingraeber, David, committee member; Funk, Vicki, committee memberGeneric delimitations within the cosmopolitan Carduus-Cirsium group (i.e., "thistles") have a long history of taxonomic confusion and debate. We present the most comprehensive molecular phylogeny of the group to date to test generic limits, reconstruct the evolution of pappus type, and elucidate the role of chromosomal evolution. We offer two solutions for the recognition of monophyletic genera: (1) consolidate all taxa into one large genus (Carduus or Cirsium), or (2) recognize each major clade as a genus (Carduus, Cirsium, Eriolepis, Notobasis, Picnomon, Silybum, and Tyrimnus). Under the second proposal, the cryptic genus Eriolepis is segregated from Cirsium, and the African Carduus are included within Cirsium. The best diagnosable morphological character to delimit the genera is pollen type, which is not practical in field-based application. We caution that prior to implementing either solution, a thorough, comprehensive morphological analysis of all current members of Cirsium sect. Epitrachys (= genus Eriolepis) be completed. Future morphological studies may find additional achene or leaf surface characters that could be used for practical field identification of the segregate genera. The data show that the plumose pappus state is symplesiomorphic for the group, with one transition to barbellate pappus, likely followed by a reversal to its ancestral state as the group colonized Eurasia. The data are consistent with a North African origin in the region of the Mediterranean and a single colonization event to North America. An ancestral chromosome state of n = 17 is hypothesized for the group, and a descending dysploidy series in Carduus is hypothesized to correspond with the aridification of the Mediterranean region. The Carduus-Cirsium group highlights the difficulty of delimiting morphologically similar, cryptic genera. Cirsium is one of the most taxonomically challenging groups of Compositae in North America. This study represents the first attempt to infer a broadly sampled phylogeny of Cirsium in North America. The two main objectives are to: (1) test whether currently hypothesized species variety complexes (C. arizonicum, C. clavatum, C. eatonii, and C. scariosum) constitute monophyletic lineages, and (2) recircumscribe any taxa that are identified as problematic. Phylogeny reconstructions based on DNA sequence data from two nuclear ribosomal regions and four plastid markers were used to infer evolutionary lineages and test species' delimitations. Eight species varietal complexes were resolved as polyphyletic. We recircumscribed these complexes and in doing so found evidence to support the recognition of six new taxa. We hypothesize that the extensive taxonomic difficulty within Cirsium is the result of several factors: 1) previously undescribed taxa, 2) inadequate representation of taxa from herbarium specimens, 3) phenotypic convergence, 4) hybridization, and 5) incipient speciation. While we can provide evidence to support the recircumscription of some taxa, others remain unresolved.Item Open Access Assessing grassland sensitivity to global change(Colorado State University. Libraries, 2015) Wilcox, Kevin Rory, author; Knapp, Alan, advisor; Kelly, Eugene, committee member; Smith, Melinda, committee member; von Fischer, Joseph, committee memberIntensification of the global hydrological cycle with atmospheric warming is expected to substantially alter precipitation regimes, and due to the tight functional relationship between precipitation and net primary productivity (NPP), these changes in climate will have large impacts on multiple NPP-linked ecosystem services such as forage production and carbon storage. At regional scales, the sensitivity of aboveground NPP (ANPP) to variation in annual precipitation increases with decreasing site-level ANPP, with this variation in sensitivity tied to turnover of plant communities over the precipitation gradient. Site-level ANPP responses are not expected to conform to regional patterns until plant communities shift, resulting in differential short- vs. long-term ANPP responses to chronically altered precipitation amounts. Although studies in grasslands have shown site-level sensitivities of ANPP to altered precipitation regimes, we lack equivalent knowledge for responses of belowground net primary productivity (BNPP) and total NPP. This will be especially important as simultaneous global change factors occur (e.g., increased fire frequency) and interact with climate change drivers to determine how the sensitivity of NPP will influence ecosystem services. My dissertation examines how plant community structure controls ecosystem sensitivity to altered precipitation amounts and patterns, and how this impacts various ecosystem services by addressing the following questions: (1) How do plant species and functional compositions control ecosystem sensitivity to altered precipitation regimes? (2) Does belowground sensitivity mirror that aboveground? And (3) What are the consequences of differential ANPP and BNPP sensitivity on biogeochemical processes in the presence of annual fire regimes? In my second chapter, I show how functional types (C₃ versus C₄ graminoids) can alter regional patterns of sensitivity to annual precipitation through differences in the timing of growth. I also show that ANPP and BNPP sensitivities can differ, but that it likely depends on vegetation and/or other attributes of an ecosystem. In chapter three, I focus on how shifts in plant species abundances, even within the same functional type, can alter sensitivity to extreme, chronic increases in precipitation. The shift in sensitivity was, again, not in agreement with regional patterns of sensitivity. Lastly, chapter four shows that the differential sensitivity of ANPP and BNPP to long term increases in precipitation can destabilize the carbon and nitrogen sequestration ability of ecosystems in the presence of extreme disturbance regimes also likely to occur in the future. Overall, my dissertation calls into question the predictive ability of regional models of NPP sensitivity under chronic shifts in precipitation amount, at least on short to moderate time scales, and I suggest that incorporation of plant community controls on above- and belowground sensitivity will be better predictors of ecosystem service responses under novel environmental conditions likely to occur in the future.Item Open Access Effects of altered seasonality on plant phenology and function in Arctic tundra(Colorado State University. Libraries, 2015) Livensperger, Carolyn, author; Wallenstein, Matthew, advisor; Steltzer, Heidi, advisor; Smith, Melinda, committee memberAltered seasonality is one of the many consequences of climate change that is affecting plant communities worldwide. Warmer temperatures, altered precipitation patterns, and changes in duration of snow cover are a few of the seasonal changes taking place. These abiotic cues are key drivers of the annual life cycles of plants, and effects of their changes vary across ecosystems, plant communities, and individual species. Regardless, changes in vegetative phenology, through earlier and/or later leaf greening and senescence, determine the timing and extent of the growing season. The consequent impacts on ecosystem function include feedbacks to local climate, changes in trophic interactions, altered nutrient cycling and plant community dynamics, and changes in plant production and carbon balance. Because Arctic ecosystems are undergoing more rapid climate change relative to lower latitudes, plant community responses there may be indicative of changes to come in other systems. In the Arctic, seasonal changes are characterized by warmer temperatures and altered duration of snow cover. While landscape-scale observations of Arctic regions suggest a general trend towards earlier onset of greening, later plant senescence, and increased aboveground production, experiments are needed to determine the species and mechanisms that are driving these trends. Over three years, we experimentally altered the timing of snowmelt and increased temperature in moist acidic tundra. We investigated plant phenological and functional response to these changes. First, we asked how early snowmelt and warming affect the timing of leaf appearance and expansion, and whether spring phenological shifts would affect aboveground production of individual species. Earlier leaf expansion and growth are expected with warmer temperatures; however, in seasonally snow-covered ecosystems, timing of snowmelt may be an additional cue of plant species green-up. We found that altered seasonality led to earlier plant growth, but aboveground plant production varied among species. Further, variation in the timing of leaf expansion across functional groups due to evolved plant strategies rather than within functional groups due to experimental climate change corresponds with patterns of increased aboveground plant production. As a result, we predict that climate change will alter plant communities by increasing the abundance of early-growing plant species, even those that do not shift the timing of leaf expansion. Second, we asked how altered seasonality would affect the timing and rate of plant community senescence, and how air and soil microclimate influences these processes. The timing of plant senescence is thought to be primarily controlled by photoperiod; however, recent studies have shown that environmental cues such as temperature and soil water content can modify timing of senescence. In the Arctic, where photoperiod decreases rapidly in August, senescence may not shift as climate warms due to strong photoperiod control. We tested alternative models of senescence to determine if microclimate (air temperature, soil temperature, and soil moisture), or start of season phenology events affect the onset and rate of community senescence. All three microclimate predictors partially explained variation in timing of onset of senescence, suggesting that photoperiod is not the sole control on this process in Arctic plant communities. Rather, increased air and soil temperatures along with drier soil conditions, led to acceleration in the onset of senescence at a community level. Our data suggest that climate change could result in a shorter peak season due to earlier onset of senescence, which could decrease potential carbon uptake in moist acidic tundra.Item Open Access Fear of humans drives complex changes in predators and prey in South Africa(Colorado State University. Libraries, 2022) Lasky, Monica, author; Bombaci, Sara, advisor; Berger, Joel, committee member; Smith, Melinda, committee memberWildlife responses to human presence vary greatly; species can be fearful of humans or habituate to human presence. Using experimental and observational methods, I investigated how South African wildlife altered species-specific behavior and predator-prey co-occurrence in response to simulated and actual human presence. I used camera traps to capture wildlife responses to human voice playbacks in areas with and without tourists, and found that wildlife variably altered space use, temporal activity, and fleeing behavior in response to human voice playbacks and tourism, which further altered predator-prey co-occurrence within the system. Human-induced fear elicited a different response from wildlife than predator-induced fear, suggesting that not all species treat humans as they would their natural predators. Furthermore, prey responded to human voice playbacks and tourists similarly, while predators had different responses to human playbacks than how they responded to tourists. Prey species may be using humans as a shield against predation regardless of the amount of time humans have been present within the system, while predators may be more fearful of a novel human stimulus but appeared to be habituated to long-occurring human presence. The eventual habituation to humans by predators reverted the initial decrease in predator-prey co-occurrence to that observed in the control sites, suggesting that eventual habituation of predators to humans may help re-establish prey access to predators in disturbed systems. However, habituation may also lead to future human-predator conflict that can impact species conservation. Finally, I conclude by providing future research directions for studying how humans can impact predator-prey interactions.Item Open Access Impacts of coarse woody debris and edge effects on Engelmann spruce regeneration(Colorado State University. Libraries, 2016) Davy, Ryan, author; Ex, Seth, advisor; Cheng, Anthony, committee member; Smith, Melinda, committee memberEngelmann spruce (Picea engelmannii Parry ex Engelm.) is a notoriously difficult species to regenerate, and there has been a history of regeneration failures following group selection cuts on the Uncompahgre Plateau. Our goal was to investigate edge effects and coarse woody debris management on regeneration success in group selection openings. Group selection is an uneven-aged system used in the West to regenerate high elevation spruce-fir forests with small (<1 ac) openings. We implemented an Engelmann spruce germination study on the Uncompahgre Plateau in group selection openings. Permanent plots were installed in spring of 2015. We altered microsite conditions by manipulating coarse woody debris amounts at varying distances from the north and south edges in combination with scarification. Findings show that the southern edge provides a benefit to spruce germination through 23 meters. Coarse woody debris was significantly beneficial at all distances from edge, and without coarse woody debris germination was extremely low.Item Open Access Impacts of compound precipitation extremes on belowground dynamics in a mesic grassland(Colorado State University. Libraries, 2021) Slette, Ingrid Jane, author; Knapp, Alan, advisor; Smith, Melinda, committee member; Iversen, Colleen, committee member; Conant, Rich, committee memberClimate change is altering precipitation regimes globally and is expected to cause more frequent and extreme droughts as well as intensification of precipitation patterns (e.g., fewer and larger precipitation events) in many regions around the world. Drought has long been a phenomenon of interest to ecologists and has been widely studied as a key driver of ecosystem dynamics. To study drought, ecologists must define or at least operationalize what constitutes drought conditions. How this is accomplished in practice is unclear, so I begin my dissertation with a literature review that assessed how ecologists describe and study drought. I found that few publications explicitly define drought and that many (~30%) provide little quantification of studied droughts at all, simply equating drought with generally dry conditions. This lack of description hampers synthesis and our ability to draw broad ecological conclusions about drought impacts. I suggest that future publications provide detailed descriptions of drought conditions and contextualization within site-specific long-term climatic history, to facilitate more rigorous comparisons among studies. Our understanding of the ecological impacts of drought is further limited by the fact that most previous research has focused on the impacts of single drought events, and it is increasingly likely that droughts will be compounded with other precipitation changes (e.g., intensified precipitation patterns or previous droughts). To study how the impacts of drought are altered when compounded with other precipitation changes, I imposed a 2-yr extreme drought (growing season precipitation reduced 66%) in two different long-term precipitation experiments at the Konza Prairie Biological Station- one which had intensified precipitation patterns by imposing a treatment of fewer and larger precipitation events with longer intervening dry periods for 16 years (chapter 2), and one which had imposed a previous extreme drought (chapter 3). I found that though precipitation pattern intensification reduced aboveground net primary production (ANPP), it did not alter the response of ANPP to a subsequently imposed drought. In contrast, previous exposure to intensified precipitation patterns reduced belowground net primary production (BNPP) and muted soil CO2 flux responses to rainfall events during drought. In the case of multiple droughts, I found that repeated drought decreased root mass production more than twice as much as one drought (-63% vs. -27%, respectively, relative to controls). Thus, in both experiments, previous exposure to precipitation change decreased the resistance of BNPP to a subsequent drought. These results suggest that drought impacts might be underestimated if precipitation history and/or belowground impacts are not fully considered. Overall, my dissertation results indicate that understanding and prediction of ecological drought effects can be improved with more detailed and consistent descriptions of drought conditions and greater consideration of past precipitation changes and belowground dynamics.Item Open Access Impacts of drought on grassland productivity across the wet-dry gradient in the U.S. Great Plains in 2010-2012(Colorado State University. Libraries, 2016) Curry, Renee A., author; Denning, A. Scott, advisor; Smith, Melinda, committee member; Peek, Lori, committee memberSevere, prolonged droughts are predicted to occur more frequently due to global climate change. Since grasslands already grow in regions that are water limited, they are particularly vulnerable to changes in precipitation. Climate models are used to investigate how grasslands will respond to climate change; however, current land surface models have difficulty in simulating grasslands and their response to drought. The main objective of this research project was to investigate the dominant relationships between grassland productivity and precipitation and to see if this behavior could be predicted in a model. To do this, we focused on both climate (dry to wet gradient) and drought (climate anomalies) using a combination of data and the Simple Biosphere Model Version 4 (SiB4). In order to have a better understanding of the relationship between grassland productivity and precipitation on a regional scale, this research studies nine sites across the U.S. Great Plains over which there is a significant precipitation gradient. In addition to the climatic gradient in precipitation, we took advantage of a natural experiment from 2010 through 2012, during which a significant drought occurred in this region. Observed west-to-east gradients in grassland productivity were generally well-captured by the model: there was an increase in leaf area index (LAI) with increasing precipitation, with a nearly identical linear relationship in both the observations and the model. SiB4 overestimated the magnitude of the seasonal-mean LAI; however, this bias was constant across the precipitation gradient. The drought decreased grassland productivity: both the observations and the model showed reduced LAI and a shorter growing season due to drought, and an analysis of the standardized anomalies in LAI and precipitation demonstrated that both the observations and the model have a nearly identical linear response to drought (difference in slope < 10%). Although SiB4 has a bias in the magnitude of seasonal-mean LAI, it has the same precipitation responses as seen in the data, thus showing the ability to capture the behavior of grasslands both across a dry-wet gradient and for a specific drought event.Item Open Access Implications of facilitation and heterogeneity for plant community restoration in the Rocky Mountain region(Colorado State University. Libraries, 2023) Harris, Rebecca F., author; Paschke, Mark, advisor; Havrilla, Caroline, committee member; Rhoades, Chuck, committee member; Smith, Melinda, committee memberSeeding is the most widespread and viable method to revegetate degraded dryland ecosystems. Despite its prevalence, efforts to establish plants through seeding frequently fail. Variable weather conditions, competition with dominant and invasive species and herbivory pose barriers to the establishment of seeded plants. As a result, there is a great need and demand for innovative restoration practices that can aid revegetation efforts. Pit, mound and slash pile treatments create spatial and resource heterogeneity and thus can provide niches for different plants to find suitable habitat. I completed a four-year study that tested the impacts of seeding in conjunction with heterogeneity treatments on measures of plant community structure and cover compared to untreated but seeded plots and unseeded controls. Research sites were located in California Park, Colorado USA, a 11,000-ha Artemisia cana (silver sagebrush) meadow in the Medicine Bow Routt National Forest. In 2018, replicated test plots containing four treatments (unseeded control, seeded only, seeded plus soil pits and mounds, and seeded plus slash) were established at degraded sites in California Park. Seeded plots received a high diversity native seed mix (39 species) at a high rate (1496 Pure Live Seed [PLS] / m2). I monitored seeded species density and total plant species cover in the summers of 2019 through 2022. I analyzed treatment effects on plant Shannon Wiener diversity (H), richness, seeded abundance (plants / m2), Pielou's evenness (J) and percent cover with linear mixed-effects models. Plots that received the seeded only and seeded plus soil pits and mounds treatments contained higher seeded species diversity than control plots in 2019 and 2022. While seeded plus slash pile treatment plots increased seeded species diversity in the first year of monitoring, this effect diminished after 2019. It is important to note, no seeded diversity differences emerged between heterogeneity treatment plots and untreated but seeded plots in any year. Findings suggest that seed application can increase the diversity of desirable seeded species and may be a useful tool to shift plant community composition. Shrub subcanopies accumulate moisture and nutrients in a manner that can facilitate understory plants. Consequently, seeding beneath shrubs may improve seedling establishment and survival in dryland ecosystems where harsh environmental conditions are present. I set up a study to evaluate whether seeded shrub islands had higher seeded species abundance and richness compared to seeded interspaces and unseeded controls. Study sites were located outside of Grand Junction, Colorado in Dominguez Escalante and McInnis Canyons National Conservation Areas (NCA) (Figure 2.1). Six sites were established in fall of 2020, three within sagebrush and three within salt desert shrublands. Five seeded shrub islands, five seeded interspaces, five unseeded shrub island controls and five unseeded interspace controls were established at each site. In addition, I evaluated if the impacts of these treatments were different between sagebrush and salt desert shrublands. Furthermore, I assessed whether plant functional groups and soil chemical properties were impacted by treatment type. I analyzed treatment effects on seeded species richness, seeded species abundance, cover by plant functional group, surface soil moisture, temperature and chemical properties with separate linear mixed-effects models. While sub canopy microsites were on average nutrient enriched and cooler than interspace plots, they did not facilitate seeded species establishment. In contrast to expectations, seeded interspaces contained higher seeded species richness than all other plot types. Lower richness in seeded shrub islands may be due to sodic, saline and or saline-sodic soil conditions found beneath shrubs within the salt desert. In addition, high cover of introduced perennial grasses beneath shrub islands may prevent seedling establishment at sagebrush sites. Results suggest that interspaces provide more favorable conditions for seeded plant establishment than shrub islands in both systems. Land managers are interested in levering positive plant-plant interactions (i.e., facilitation) and heterogeneity to improve seeded plant establishment and plant community restoration outcomes. I investigated whether applying a native seed mix either beneath shrub islands, or in tandem with heterogeneity treatments, increased seeded plant establishment and diversity respectively. I hope this research can contribute to improving plant community restoration outcomes in degraded dryland ecosystems.Item Open Access Influence of water sources on vegetation and geomorphic conditions of first order streams in Glacier National Park, Montana, USA(Colorado State University. Libraries, 2015) McKernan, Cristina E., author; Cooper, David J., advisor; Schweiger, E. William, committee member; Smith, Melinda, committee memberIn 1850 at the end of the Little Ice Age, 150 glaciers existed in Glacier National Park (GNP), MT. In 2010, only 25 remained. Climate warming in mid-high latitudes and mountain regions, like GNP, is occurring more rapidly than any other place on Earth. This warming is causing extensive loss of glaciers and snowpack and in high elevation watersheds, glacier melt water exerts substantial influence on hydrogeomorphic processes producing floods, landslides, and debris flows. Rising temperatures will have short term and long term effects on stream flow from melting glaciers including increases in peak flows, stream temperature, and an increased potential for hydrogeomorphic hazards like rock avalanches, landslides, rock fall, glacial moraine dam failure, and outburst floods. From an ecological perspective changes in stream flow and geomorphic activity are important disturbances that form and maintain riparian wetlands. Riparian wetlands occupy a relatively small percentage of mountain landscapes but are important and highly sensitive ecosystems worldwide. The goal of this study was to 1) assess geomorphic conditions of first order stream types 2) identify plant community composition along first order stream types and 3) determine the importance of hydrogeomorphic conditions, topography, and water chemistry in explaining high elevation riparian plant community patterns. To do this, I surveyed vegetation and geomorphic conditions of first order streams directly connected to glaciers, snowfields, and springs. Vegetation data was analyzed at reach and plot (1 m²) scales. Reach scale vegetation was grouped into four plant communities and plot scale vegetation was grouped into seven communities using hierarchical cluster analysis and indicator species analysis. Two of both reach and plot scale communities were characterized by an abundance of Salix species (willow). Non-metric multidimensional scaling was used to investigate relationships between stream types and hydrogeomorphic variables as well as plant community occurrence and abiotic variables. Permanova analysis was used to identify statistically significant hydrogeomorphic and vegetation differences in stream types. Hydrogeomorphic variables, particularly stream discharge was a proxy for disturbance and important in explaining variation in plant community patterns. Glacier streams typically had higher stream discharge values and higher frequencies of Salix communities compared to snow or spring fed sites. This research demonstrates the importance of glaciers in controlling hydrogeomorphic conditions and riparian plant community patterns and addresses threats to riparian communities as a result of retreating glaciers. Understanding the potential influences of climate induced changes in the hydrologic drivers of riparian wetlands is a critical topic with implications for channel stability, flood control, water chemistry, and biodiversity, all high priority concerns for GNP.Item Unknown Is it plastic or just fantastic? Understanding the role of plasticity and local adaptation in the drought tolerance of Bouteloua gracilis(Colorado State University. Libraries, 2017) Bushey, Julie A., author; Ocheltree, Troy, advisor; Smith, Melinda, committee member; Gleason, Sean, committee memberThe ability of an organism to tolerate or acclimate to drought may become a major driver of changes in community composition, carbon and water cycles and ecosystem services as we encounter increasing severity and frequency of droughts in the face of global change. Drought tolerance traits allow us to quantify functional attributes of individual species, but the expected variability of drought tolerance traits within a species is uncertain. Although some variability in plant traits are expected, it is unknown whether the local adaptation of populations can explain the expected variability. The objective of this study is the quantification of plasticity of drought tolerance responses across populations of Bouteloua gracilis to different soil moisture levels. B. gracilis is a C4 perennial grass that dominates grasslands across a range of climates and is a major contributor of ecosystem function and services within these systems. Populations from less arid sites showed greater osmotic adjustment and higher midday water potentials when grown under limited soil moisture conditions. Populations from arid sites did not adjust osmotic potential but showed more negative midday water potentials while maintaining higher growth rates. This variation in response to lowered soil moisture indicates a potential shift in water use strategy across an aridity gradient that has implications for land managers seeking to restore B. gracilis dominated ecosystems with drought tolerant material.Item Unknown Lessons in establishing plant communities on constructed fens for oil sands mine reclamation(Colorado State University. Libraries, 2018) Borkenhagen, Andrea, author; Cooper, David J., advisor; Paschke, Mark, committee member; Vitt, Dale, committee member; Smith, Melinda, committee memberThe third-largest proven oil deposit in the world is in Alberta, underlying 142,000 square kilometers of Canada’s boreal covered by forested uplands and peatland basins. The vast deposit is in the form of oil sands that consist of a mixture of sand, water, clay and oil. Where oil sands are near surface, they are excavated in open-pit mines that remove the overburden landscape to extract the resource. Reclamation is a legislative condition for oil sands operators to replace ecosystems that are lost. This involves recontouring the surface to recreate landscape processes and introducing plant species common in regional reference sites. Fen peatlands are the most dominant ecosystem type but provincial standards have allowed compensation with marsh wetland as they are easier to create. Oil sands extraction and reclamation is highly controversial with opponents suggesting that destroyed peatlands will not be restored. Scientists, operators and regulators are more aware that peatland reclamation is critical and despite the constraints, research is underway in two reclamation fens that have recently been constructed. To effectively reclaim fens, we need to understand how plant species and communities respond to environmental gradients, the most effective methods to introduce species, and which success criteria are achievable. In the following chapters, I examine drivers of plant community assembly in natural and reclaimed fens and consequences of abiotic, biotic, and construction constraints on ecosystem structure and function. A major constraint in fen reclamation is achieving optimal surface topography and seasonal water table position to support desired plants. Moss-dominated fens are the most common regional peatland type and evaluating the response of mosses to submergence in natural fens provides insight into species selection and processes of recovery for reclaimed fens. I conducted a field experiment to determine the short and long-term tolerances of four fen mosses to submergence from 1 to 8 weeks. I found that moss species vary in their responses to submergence duration and that shifts in community composition that support tolerant dominant species such as Tomentypnum nitens increased moss community resilience and provide stability in boreal fen ecosystems. As part of a multi-stakeholder collaboration, the first self-sustaining reclamation fen and associated watershed was constructed within an oil sands mine site north of Fort McMurray, Alberta. To determine the most effective approach to establish fen plants, I designed and implemented a large-scale multifactorial field experiment that tested introducing moss layer transfer material (MLT), seeds, and seedlings under wood-strand mulch and with a Typha latifolia weeding treatment. Four years after planting, the MLT and Juncus balticus seedling treatment supported the highest fen bryophyte and vascular plant cover and species richness. Weeding did reduce T. latifolia cover but was not necessary in areas where seedlings or MLT was introduced. The most successful fen species to establish was C. aquatilis, which rapidly colonized but also reduced cover and richness of bryophytes and other vascular plants. To provide a broader context, I examined vegetation establishment across the two reclaimed fens that had different water level gradients and species introduction approaches. Despite differences, peat-accumulating bryophyte and vascular plant communities developed in both fens. Community convergence occurred due to dominance of C. aquatilis, and community divergence occurred in response to water level gradients. Dominant species adapted to site conditions can be introduce by basic approaches such as seeding. Intensive approaches such as planting seedlings or spreading MLT should be prioritized in areas of overlap along water level gradients between desirable and undesirable communities to deter establishment of non-peat forming species. Bryophyte cover and desirable species richness was highest following intensive approaches and where the summer water level was -10 cm to -40 cm from the soil surface. My research shows that it is possible to reclaim peat-accumulating bryophyte and vascular plant communities in the post-mining landscape of Alberta and that a range of successful outcomes are achievable. Previous assertions that fens cannot be reclaimed after mining activities are antiquated as large-scale construction designs and species introduction approaches are actively underway and the results are proven.Item Open Access Plant-mediated interactions among gall forming insects(Colorado State University. Libraries, 2020) Barosh, Theresa, author; Ode, Paul, advisor; Bean, Dan, committee member; Smith, Melinda, committee member; Kondratieff, Boris, committee memberRussian knapweed (Rhaponticum (=Acroptilon) repens (L.) Hidalgo) is one of the most troubling exotic weeds throughout the western United States invading many public and private lands. A classical biological control agents, the gall midge (Jaapiella ivannikovi Fedotova), is a parasite on Russian knapweed, forming galls on the plant, inside which J. ivannikovi broods feed and develop. This system provides an opportunity to consider plant-mediated interactions between midge individuals and considered the merits of integrating other weed management techniques (grazing, mowing, and chemical control before insect release) with biological control. To accomplish this, I conducted releases of gall midge agents at replicated sites throughout Colorado, field cage experiments with simulated grazing, and greenhouse studies. We found that J. ivannikovi initially established across Colorado, however, failed to maintain populations in subsequent years. Interestingly, grazing increases J. ivannikovi establishment. Of further note, J. ivannikovi broods compete with one another even when feeding on different parts of the plant. The results of these experiments indicate that integrating management techniques can increase biocontrol agent establishment. I also question how effective this midge is at reducing Russian knapweed flowering and vegetative growth in the field. This research resulted in recommendations regarding the most judicious use of J. ivannikovi biocontrol agents in terms of where and when agents are most effective for management, and practitioners at the Colorado Department of Agriculture Palisade Insectary have adjusted their strategies accordingly.Item Unknown Plant-mediated interactions between herbivory and soil microbial communities in biocontrol programs of Russian knapweed(Colorado State University. Libraries, 2024) Matos Franco, Giovana, author; Ode, Paul, advisor; Pearse, Ian, committee member; Smith, Melinda, committee member; Trivedi, Pankaj, committee memberRussian knapweed (Rhaponticum repens) is an invasive noxious weed present in the United States and two insect biocontrol agents have been released to assist with its management: the gall midge (Jaapiella ivannikovi) and the gall wasp (Aulacidea acroptilonica). Since their establishment, no concrete impacts of biocontrol agents onto Russian knapweed have been measured, neither their impacts on interactions between Russian knapweed and local microbiomes. To address this knowledge gap, observational and manipulative studies were conducted to investigate the effects of biocontrol agents on Russian knapweed fitness as well as its associated microbiomes. We found that Russian knapweed associates with a core microbiome that can assist with invasion in the introduced range as well as, in root samples collected from sites where gall wasp were present, lower microbiome diversity was observed, indicating potential negative effects on overall plant health. In garden conditions, water availability positively correlated with plant growth, negatively correlated with insect establishment, and shaped microbiomes in root associated tissues. Results of this dissertation highlights how introduction of biocontrol agents shifts pre-established relationships between invasive plants and microbiomes as well as how such relationships could be impacting the success of biocontrol programs.Item Unknown Restoring island birds and seed dispersal in New Zealand's fenced mainland island sanctuaries(Colorado State University. Libraries, 2018) Bombaci, Sara Petrita, author; Pejchar, Liba, advisor; Reed, Sarah, committee member; Savidge, Julie, committee member; Smith, Melinda, committee memberIsland ecosystems are global biodiversity hotspots, but many island species face population declines and extinction. These losses are mainly driven by invasive mammals that consume or compete with native animals and degrade their habitats. The decline of island animal populations may also impact ecosystem processes that depend on them, e.g. seed dispersal, pollination, and nutrient cycling. The island nation of New Zealand has pioneered a unique solution – fenced mainland island sanctuaries – which exclude invasive mammals from natural habitats and provide opportunities to restore native birds and other wildlife. Yet, critics question whether sanctuaries, which are costly and require continuous maintenance, effectively conserve birds and ecosystems, given minimal research on sanctuary project outcomes. I assessed if sanctuaries are an effective conservation tool for restoring birds and seed dispersal in New Zealand. I compared bird population densities and bird-mediated seed dispersal in three fenced sanctuary sites to three paired reference sites (with minimal mammal control). From January-April 2016 and 2017, I set seed traps to measure dispersed-seed abundance, conducted focal tree observations to determine foraging rates for six tree species, and used distance sampling-based point counts to survey birds at randomly placed sampling locations within each site. I supplemented my bird surveys with a paired acoustic sampling method that uses acoustic recorders to increase survey sample size when estimating population densities with distance sampling. I tested the effectiveness of paired acoustic sampling for monitoring New Zealand forest bird populations by assessing whether density estimates from acoustic data were biased relative to densities estimated from human point counts, and by assessing whether the paired acoustic sampling method corrects bias from acoustic data, when present. Thus, the objectives of this dissertation were to assess 1) whether audio data could be used to estimate population densities for New Zealand forest birds (Chapter 1), 2) whether fenced mainland island sanctuaries increase the density of native or introduced bird species relative to unprotected areas in New Zealand (Chapter 2), and 3) whether sanctuaries enhance bird-mediated seed dispersal (foraging rates and dispersed-seed abundance) relative to unprotected areas (Chapter 3). I found that acoustic recorders underestimated bird population densities for four bird species but incorporating statistical offsets from the paired sampling method in generalized linear mixed models corrected the bias for all four species. Across both years, I found 0.27 to 9.00 more birds/ha on average for nine of twelve native bird species (including seven frugivores) in sanctuaries compared to unprotected sites, and no difference in mean population densities for three introduced bird species (two frugivores) and three biogeographically recent native species (one frugivore). Mean foraging rates and dispersed seed counts were also higher (0.1-0.6 more fruits consumed/observation period; 2-22 more seeds dispersed/plot) in sanctuary sites for several native tree species. Frugivore density, or both frugivore density and fruit abundance were significant positive predictors of foraging rates and dispersed seed counts for most tree species. Finally, native bird densities were correlated with foraging rates and dispersed seed counts for most tree species, but introduced bird densities were rarely correlated with foraging or dispersed seed counts. Thus, higher densities of native frugivorous birds in sanctuary sites appears to have resulted in increased fruit removal and dispersed seed counts for several native tree species. My study is one of the first to demonstrate that fenced mainland island sanctuaries, which require a substantial investment of conservation funds, are meeting ecological objectives. Furthermore, I demonstrate that paired acoustic sampling can be used to produce unbiased population density estimates from acoustic data, relative to human point counts, which holds great promise for increasing the scope and efficiency of bird population monitoring in New Zealand. I show that sanctuaries increase bird population densities for several native bird species and have no effect on introduced and biogeographically recent native species. These findings support predictions made over a decade ago on the potential 'winners' and 'losers' of mammal eradication and offer evidence that fenced sanctuaries effectively conserve New Zealand's native bird populations. By increasing bird densities and seed dispersal, fenced mainland island sanctuaries could be a viable tool for restoring other island and mainland ecosystems under threat from invasive mammals.Item Open Access Temperature sensitivity as a microbial trait(Colorado State University. Libraries, 2017) Alster, Charlotte J., author; von Fischer, Joseph, advisor; Cotrufo, Francesca, committee member; Smith, Melinda, committee member; Wallenstein, Matthew, committee memberReaction rates in biological systems are strongly controlled by temperature, yet the degree to which temperature sensitivity varies for different enzymes and microorganisms is being largely reformulated. The Arrhenius equation is the most commonly used model over the last century that predicts reaction rate response with temperature. However, the Arrhenius equation does not account for large heat capacities associated with enzymes in biological reactions, thus creating significant deviations from predicted reaction rates. A relatively new model, Macromolecular Rate Theory (MMRT), modifies the Arrhenius equation by accounting for the temperature dependence of these large heat capacities found in biological reactions. Using the MMRT model I have developed a novel framework to assess temperature sensitivity as a biological trait through a series of experiments. This work provides evidence that microbes and enzymes can have distinct heat capacities, and thus distinct temperature sensitivities, independent of their external environment. I first assessed temperature sensitivity of soil CO2 production from different soil microbial communities and then worked with pure cultures to examine temperature sensitivity of enzyme activities from soil microbial isolates. From these experiments I determined that temperature sensitivity varies based on genetic variation of the microbe and substrate type as well as examined the importance of using MMRT over the Arrhenius equation. Finally, I used a meta-analysis to analyze the distribution of temperature sensitivity traits to look across a variety of biological systems (e.g., the food industry, wastewater treatment, soils). I found that temperature sensitivity traits vary with organism type, environment, process type, and biodiversity. Exploring temperature sensitivity as a trait allows for new insights of soil microbes from an ecological perspective as well has the potential to inform ecosystem climate models.Item Unknown Temperature sensitivity in aboveground net primary productivity in semi-arid grasslands(Colorado State University. Libraries, 2014) Mowll, Whitney Macy, author; Knapp, Alan, advisor; Smith, Melinda, committee member; Hess, Ann, committee memberAlthough climate models forecast warmer temperatures with a high degree of certainty, precipitation is the primary driver of aboveground net primary productivity (ANPP) in most grasslands. In contrast, variations in temperature seldom are related to patterns of ANPP. Thus forecasting responses to warming is a challenge, and raises the question: how sensitive will grassland ANPP be to warming? I evaluated climate and multi-year ANPP data (67 years) from eight western US grasslands arrayed along substantial mean annual temperature (MAT, ~7-14 °C) and mean annual precipitation (MAP, ~300 - 500 mm) gradients. I used regression and analysis of covariance (ANCOVA) to assess relationships between ANPP and temperature, as well as precipitation (annual and growing season) to evaluate temperature sensitivity of ANPP. I also related ANPP to the Standardized Precipitation Evaporation Index (SPEI), which combines precipitation and evapotranspiration estimates. Regression models indicated that variation in growing season temperature was negatively related to total and graminoid ANPP, but precipitation was a better predictor than temperature. Growing season temperature was also a significant parameter in more complex models, but again precipitation was consistently a stronger predictor of ANPP. Surprisingly, neither annual nor growing season SPEI was as strongly related to ANPP as was precipitation alone. I conclude that warming will affect ANPP in these grasslands, but that predicting temperature effects from natural climatic gradients is difficult. This is because unlike precipitation, warming effects are likely to be complex and site specific as well as moderated by regional shifts in the C3/C4 ratios of plant communities.Item Open Access Using remotely sensed fluorescence and soil moisture to better understand the seasonal cycle of tropical grasslands(Colorado State University. Libraries, 2017) Smith, Dakota Carlysle, author; Denning, A. Scott, advisor; Smith, Melinda, committee member; O'Dell, Christopher, committee member; Kummerow, Christian, committee memberSeasonal grasslands account for a large area of Earth's land cover. Annual and seasonal changes in these grasslands have profound impacts on Earth's carbon, energy, and water cycles. In tropical grasslands, growth is commonly water-limited and the landscape oscillates between highly productive and unproductive. As the monsoon begins, soils moisten providing dry grasses the water necessary to photosynthesize. However, along with the rain come clouds that obscure satellite products that are commonly used to study productivity in these areas. To navigate this issue, we used solar induced fluorescence (SIF) products from OCO-2 along with soil moisture products from the Soil Moisture Active Passive satellite (SMAP) to "see through" the clouds to monitor grassland productivity. To get a broader understanding of the vegetation dynamics, we used the Simple Biosphere Model (SiB4) to simulate the seasonal cycles of vegetation. In conjunction with SiB4, the remotely sensed SIF and soil moisture observations were utilized to paint a clearer picture of seasonal productivity in tropical grasslands. The remotely sensed data is not available for every place at one time or at every time for one place. Thus, the study was focused on a large area from 15° E to 35° W and from 8°S to 20°N in the African Sahel. Instead of studying productivity relative to time, we studied it relative to soil moisture. Through this investigation we found soil moisture thresholds for the emergence of grassland growth, near linear grassland growth, and maturity of grassland growth. We also found that SiB4 overestimates SIF by about a factor of two for nearly every value of soil moisture. On the whole, SiB4 does a surprisingly good job of predicting the response of seasonal growth in tropical grasslands to soil moisture. Future work will continue to integrate remotely sensed SIF & soil moisture with SiB4 to add to our growing knowledge of carbon, water, and energy cycling in tropical grasslands.