Scholarship & Research
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/1
Browse
7 results
Search Results
Item Investigating the ability of arbuscular mycorrhizal fungi to mitigate the negative effects of warming and drought on native perennial forbs(Montana State University - Bozeman, College of Letters & Science, 2022) Eggers, Jessica Avery; Chairperson, Graduate Committee: Laura Burkle; This is a manuscript style paper that includes co-authored chapters.The ability of arbuscular mycorrhizal fungi (AMF) to mitigate the negative effects of warming and drought on plant hosts is known for crop species but is poorly understood for native, perennial forbs. Examining the indirect influence of AMF on forbs' responses to these stressors will provide a more complete understanding of how native forbs will be affected by climate change. In an experimental greenhouse study, we inoculated two native forb species (Achillea millefolium and Linum lewisii) with three separate AMF species (Rhizophagus clarus, Claroideoglomus etunicatum, and Gigaspora rosea), then exposed plants, including an uninoculated control treatment, to varying degrees of drought and heat stress in a factorial design. We tested the effects of warming or drought treatments on plants' physical, floral, phenological, and physiological traits, including biomass, height, floral abundance, flower size, first date of flowering, floral scent, and photosynthetic performance. For both forbs, AMF ameliorated the negative effects of drought and warming on plant survival and vegetative growth, but the magnitude of effect was specific to the forb species, climate treatment, and AMF inoculant. AMF also produced changes in forb phenology, floral scent (volatile organic compounds), and flowering success and duration, which have broad implications for plant-pollinator interactions and the links between belowground and aboveground symbioses. Together, these results indicate that AMF can assist native forbs in surviving, growing, and reproducing in a warmer and drier climate.Item Impacts of a non-native forb, Alyssum desertorum Stapf., and non-target effects of Indaziflam in the sagebrush steppe of Yellowstone National Park(Montana State University - Bozeman, College of Agriculture, 2021) Meyer-Morey, Jordan; Chairperson, Graduate Committee: Lisa J. RewNon-native plants can reduce biodiversity and disrupt essential ecosystem services and functions. For most non-native plant species however, quantitative evidence of negative effects is lacking, as are fundamental demographic details; such information can inform whether and at what growth stage to implement control. Control strategies can also negatively impact non-target native plant communities; therefore, evaluating the tradeoffs of management and understanding the actual impacts of the invader is essential. I sought to understand the life history, and evaluate the competitiveness and impacts of the non-native annual forb, Alyssum desertorum Stapf., as well as non-target effects of management, across an elevation gradient in a cool, mountain sagebrush (Artemisia tridentata ssp. vaseyana (Rydb.) Beetle) steppe plant community. Seed viability, fecundity, overwintering success, and likelihood of reaching reproductive maturity of A. desertorum all declined as elevation increased; all life stage transition rates were high, suggesting that targeting seed production or fall germination would be the most effective means for control of this species. Replacement series experiments revealed that A. desertorum is a weak competitor with functionally similar species. Additionally, in the field, the presence of A. desertorum did not affect species richness nor Shannon's diversity aboveground or in the soil seedbank, and functionally similar native annual forbs were not displaced in invaded areas. I evaluated the efficacy and non-target effects of the pre-emergent herbicide, indaziflam, in diverse sagebrush steppe with localized infestations of A. desertorum across an elevational gradient. While indaziflam effectively controlled A. desertorum for two years, the richness and diversity of the surrounding community was reduced. Indaziflam inhibited recruitment of forbs, both in the field and in the seedbank. As indaziflam provides residual control of the soil seedbank for up to three years, my results suggest the future community composition may be altered, particularly native annual forb populations. Considering the weak competitive ability of A. desertorum, the species' minimal impacts to richness and diversity, and the negative effects of indaziflam to annual native forb species, I conclude that the non-target effects of indaziflam would outweigh any benefits to controlling A. desertorum in intact sagebrush steppe.Item Impacts of dryland farming systems on biodiversity, plant-insect interactions, and ecosystem services(Montana State University - Bozeman, College of Agriculture, 2018) Adhikari, Subodh; Chairperson, Graduate Committee: Fabian D. Menalled; Laura Burkle (co-chair)Farming system impacts the structure and functioning of associated biodiversity and plant-insect interactions. However, the extent of these impacts is largely unknown in drylands of the Northern Great Plains, an important region for cereal, pulse, oilseed, and forage production. Using three complementary studies, I compared the impacts of conventional and organic systems on associated biodiversity (weeds, bees, insect pests, and parasitoids), bee-flower networks, and bumblebee colony success. First, I assessed stem cuts by and parasitism on Cephus cinctus (wheat stem sawfly) in spring and winter wheat cultivars grown in conventional and organic fields. I found that organic fields had less C. cinctus infestation and more braconid parasitoids of C. cinctus, indicating an increased pest regulation in organic system. I compared C. cinctus preference and survival on Kamut with Gunnison and Reeder wheat cultivars and found the lowest C. cinctus oviposition and survival in Kamut, suggesting that Kamut is a potential genetic source for this pest. Second, I assessed the impacts of conventional and organic systems on forb and bee communities. I found greater forb diversity and more connected bee-flower networks in organic fields, but bee communities did not differ between systems. Comprising only 12% of the landscape, natural habitat did not affect small-bodied bees in either system but had a positive effect on large-bodied bees at the scale of 2000 m radius. These results indicate that an increased forb diversity and bee-flower interaction in organic fields is not enough to offset the negative effects of landscape homogeneity on bees. Third, I compared Bombus impatiens colony success, worker condition, and colony-collected pollen between farming systems. I found greater growth rate, brood cells, and pollen species richness in B. impatiens colonies as well as lower wing wear and greater body lipid mass in workers from organic fields, than in conventional fields. The greater colony success and better worker conditions could be a proxy for better ecosystem services provided by organic fields. Overall, my studies show that organic farming supports greater associated biodiversity, more complex bee-flower networks, and better biodiversity-based ecosystem services in the Northern Great Plains.Item Can targeted cattle grazing increase abundance of forbs or arthropods in sage-grouse brood-rearing habitat?(Montana State University - Bozeman, College of Agriculture, 2018) Payne, Jarrett MacKenzie; Chairperson, Graduate Committee: Jeffrey C. MosleySuboptimal brood-rearing habitat often limits greater sage-grouse (Centrocercus urophasianus) populations in western North America. In mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle) brood-rearing habitat, dense sagebrush canopy cover (> 25% cover) may limit the understory forbs and arthropods that sage-grouse prefer to eat during summer. Targeted cattle grazing is a potential habitat management tool to reduce dense sagebrush. This study evaluated targeted cattle grazing on a landscape scale to increase forbs and arthropods within core sage-grouse brood-rearing habitat. Objectives of this study were to evaluate how well targeted cattle grazing reduced mountain big sagebrush canopy cover, increased forb abundance and diversity, and increased arthropod abundance. Targeted cattle grazing was applied within two large, contiguous pastures (625 ha each) in the Beaverhead Mountains of southwestern Montana. The two pastures were grazed simultaneously at a light stocking rate (6.25 ha/AUM) for two weeks each year in mid-October 2015 and 2016. Vegetation and arthropod responses were measured during the following June-early July (2016 and 2017, respectively) within 32 microsites where mountain big sagebrush canopy cover exceeded 30% pre-treatment. Microsites were 0.008 ha to match the spatial scale at which sage-grouse broods select fine-scale habitat. One of two treatments was randomly assigned to each microsite: a low moisture block protein supplement or no supplement (unsupplemented). In the first summer after treatment, supplemented microsites averaged 78% less sagebrush canopy cover (8% vs. 36%; P < 0.001) and 25% more forb canopy cover (15% vs 12%; P = 0.122). Sage-grouse forb canopy cover was 50% greater in supplemented microsites (3% vs. 2%; P = 0.003). Forbs also comprised a greater proportion of the herbaceous understory in the supplemented vs. unsupplemented sites (48% vs. 36%; P = 0.002). Arthropod abundances were greater in supplemented than unsupplemented microsites only during the wet year of 2017 when arthropods were 1.7-1.8x more abundant in supplemented microsites. Sagebrush canopy cover was reduced by cattle trampling, not browsing. My results demonstrate that targeted cattle grazing can increase abundance of forbs and arthropods in mesic, dense stands of mountain big sagebrush in sage-grouse brood-rearing habitat.Item The influence of post-wildfire logging on forb and pollinator communities and forb reproductive sucess, Gallatin National Forest, Montana(Montana State University - Bozeman, College of Letters & Science, 2016) Heil, Laura Jean; Chairperson, Graduate Committee: Laura BurklePollinators are in decline worldwide, and these declines have implications for flowering plants and their reproduction, given that 80% of flowering plants depend on insects for pollination. One potential contributor to pollinator species' declines is shifts in disturbance regimes, such as increased severity and frequency. Wildfires are essential natural disturbances that are important drivers of forest biodiversity in the western U.S., and there is often pressure to respond to wildfire with management including post-wildfire logging. This management strategy involves the removal of dead trees for economic value immediately following wildfire. Thus, is expected that post-wildfire logging has additional impacts on forest communities compared to non-salvage logging, and that it impacts forb and pollinator communities. Several studies have examined the short-term responses of forb and pollinator communities to wildfire and non-salvage logging individually, and one study examined their combined effects. However, no studies have examined the long-term effects of post-wildfire logging, on forb and pollinator communities and on forb reproduction. My research addresses these gaps in knowledge and asks: 1) how do floral and bee communities respond to post-wildfire logging and how do their responses differ between two different-aged fires, and 2) how does post-wildfire logging influence forb reproduction and pollen limitation of reproduction in an older wildfire? In the more recent fire, floral and bee density and species richness were higher in logged than unlogged areas. By contrast, in the older fire, forb and bee communities were similar between logged and unlogged areas. Unexpectedly, we found large inter- and intra-annual variation in the effects of post-wildfire logging. Lastly, in the older fire, there were no effects of post-wildfire logging on forb reproduction, but plants were pollen limited in unlogged areas. This suggests that plants in unlogged areas are able to augment their reproductive output with supplemental pollen resources, but plants in logged areas cannot. Together, these results suggest that post-wildfire logging is beneficial for forbs and pollinators in the short-term, and these positive effects depend on time of growing season and sampling year. However, post-wildfire logging may be detrimental for forb reproduction in the long-term.Item Biogeochemical and plant functional group response to long-term snow manipulation in a subalpine grassland(Montana State University - Bozeman, College of Agriculture, 2013) Holsinger, Jordan Paul; Chairperson, Graduate Committee: Jack BrookshireSnow represents an important control over plant communities in seasonally snow-covered ecosystems. It constrains the growing season and affects the availability of important resources including water, nitrogen (N) and phosphorus (P). Snow depth, distribution and duration have been affected by global climate change making it increasingly important to understand the effects of changing snow regimes on terrestrial ecosystems. Here we leverage a 43-year snow manipulation experiment to examine the effects of long-term changes in snow depth on plant community structure, resource availability and interactions therein in a common grassland type of the northern Rocky Mountains in western North America. Long-term experimental doubling and quadrupling of snowpack was associated with a significant shift in plant functional group distribution to a more forb rich community. Snow addition has resulted in a two to three-fold increase in forb to grass biomass ratios over time. Forbs consistently had greater N and P contents and lower nutrient use efficiencies compared to grasses. Forbs also displayed higher rates of net photosynthesis relative to grasses and sustained positive carbon (C) fixation rates late into the growing season after grasses had ceased. Though there is evidence that water exerts considerable control over ecosystem processes, increased snow depth did not have affect soil water availability through the growing season. However, snow depth was associated with significant differences in plant-available phosphate across the entire growing season with approximate 15% and 31% increases in pools of available P relative to ambient snowpack depth for doubled and quadrupled snowpacks respectively. Estimates of direct P inputs via dust and the ratio of available P to total P in the soil suggest that internal cycling was largely responsible for the observed differences in pools of available P. However, growing season net mineralization rates do not differ across treatments. This may suggest that winter processes make significant contributions to nutrient cycles. It is possible that the increased availability of P favors the shift to a forb-rich community under deeper snow because of their increased productivity under dry conditions and that the increased litter quality of forbs likewise promotes increased litter decomposition and mineralization, especially of P.Item Influence of native bunchgrass and invasive forb litter on plant growth in a semi-arid bunchgrass prairie(Montana State University - Bozeman, College of Agriculture, 2006) Hoopes, Carla; Chairperson, Graduate Committee: Cliff Montagne.Litter can influence plant species diversity. I investigated plant litter effects for density, cover, and biomass on common St. Johnswort Hypericum perforatum L., a nonnative- species-group, and a native-species-group. The following hypotheses were tested: litter source would favor species dominant in the litter; the high amount of litter (908 grams) would decrease density more than the moderate amount (454 grams); coarse size litter would decrease density more than fine size; and the effect of litter would depend upon interactions of all three variables. Above-ground plant material was removed from two adjacent sites, one a native bunchgrass prairie (native site), the other infested with St. Johnswort (invasive site). Three-way litter treatments were applied in October 1999 and reapplied in July 2000 in combinations of high- or moderate-amount of litter, native or St. Johnswort species by source, and fine or coarse texture by size. Sampling occurred at peak standing crop July 2000 and 2001. Analysis of variance in 2001 data results follow. St. Johnswort was decreased by its own litter (all P <.06). St. Johnswort and native species were detrimentally influenced more by the high amount of litter than by the moderate amount (all P <.05). Although litter size did not influence St. Johnswort, native species biomass was more detrimentally influenced by coarse size litter than by fine (P <.05). When we added more fine size litter, native species were more detrimentally influenced than when we increased the amount of coarse litter (P <.06). In the invasive site, moderate amounts of coarse native litter decreased St. Johnswort. High amounts of coarse St. Johnswort litter decreased it even more (both P <.05). The opposite effects were found for native species (both P <.05). In the native site, the only treatment that reduced St. Johnswort more than no litter was the high amount of fine St. Johnswort litter (P <.05). The same fine St. Johnswort litter in moderate amounts was the only treatment that did not decrease native species (P <.05). The complexity of litter influence through interactions of amount, source, and size detrimentally and non-detrimentally caused changes to plant species diversity at each site (all P <.05).