Browsing by Author "Paschke, Mark W., advisor"

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Open Access
An integrated eco-socio-economic analysis of forest transition and forest restoration in Vietnam
(Colorado State University. Libraries, 2018) Khuc, Quy Van, author; Paschke, Mark W., advisor; Pham, Dien V., advisor; Loomis, John B., committee member; Cheng, Antony S., committee member
Forests provide numerous benefits to human well-being, so changes in forest cover have large societal impacts from local to global scales. Several studies in Vietnam and elsewhere have found single solutions for increasing forest cover. However, a comprehensive solution for harnessing forest restoration to satisfy growing demands for sustainable global development that improves rural community livelihood, enhances biodiversity and environmental services, and mitigates climate change is lacking. This dissertation focuses on obtaining a deeper understanding of forest transition, forest restoration, and their proximate drivers as well as trade-offs of land use in upland forests in Vietnam. This dissertation is a collection of four independent studies. The first study quantified the drivers of deforestation and forest degradation at a national scale in Vietnam. Results show that around 1.77 and 0.65 million hectares of forests were lost or degraded, respectively, between 2000 and 2010. Deforestation and forest degradation declined in Vietnam between 2000 and 2010, but these processes remain significant. The extent and magnitude of deforestation and degradation vary across provinces and were most notable in the north central, northeast, central highland, and northwest areas of the nation. Poverty, initial forest cover, governance, and population growth were the top drivers of deforestation and degradation. The second study investigated the extent of forest restoration and its proximate drivers at the local-communal scale in Vietnam's Dien Bien Province. Geographic information system (GIS) tools, a structural regression model based on forest cover maps, and a field survey were employed while numerous socio-economic variables that were potentially associated with forest restoration were examined. I found that around 118,000 hectares of forests were restored between 1990 and 2010. Restored forest comprised the largest share (above 84%) of total forest gain and this share increased from 1990-2000 to 2000-2010. Expansion of restored forest was mainly driven by the presence of migration, lower population density, higher income, and the implementation of forestry policies. The third study explored the willingness of urban households to support forest restoration in Vietnam. I randomly surveyed over 200 households in the capital city Hanoi and a maximum likelihood estimator model was used to obtain the parameters of a model to quantify willingness-to-pay (WTP) for a program of forest restoration. Over forty percent of the households surveyed were willing to pay for forest restoration. As well as quantified determinants of WTP, my findings suggest that either improving households' income and educational level or focusing on females in the family may represent untapped sources of restoration funding among urban households. Finally, in a fourth study, the potentials and challenges of climate change mitigation programs in the north central region of Vietnam demonstrate possible scenarios associated with many levels of uncertainty. The role of plantation forests in total household income was quantified, trade-offs between shifting cultivation and plantation forests were analyzed and the factor groups that constrain plantation forest expansion were highlighted. My empirical results offer several important policy implications, not only for forest restoration practices as part of forest-based climate change mitigation programs but also for sustainable mountainous rural livelihood development in Vietnam and beyond.
Open Access
An investigation of nitrogen fixation by Russet buffaloberry in Colorado conifer forests
(Colorado State University. Libraries, 2011) Miller, Zoe May, author; Paschke, Mark W., advisor; Binkley, Daniel E., committee member; Rhoades, Charles C., committee member; Stromberger, Mary E., committee member
Russet buffaloberry (Shepherdia Canadensis (L.) Nutt.) is an actinorhizal shrub capable of forming a symbiotic relationship with the N2-fixing soil actinomycetes Frankia. Actinorhizal shrubs are important species as they are able to fix an ecologically significant amount of N and can inhabit disturbed sites with infertile soils. Buffaloberry is commonly found as a dominant understory species in lodgepole pine (Pinus contorta Douglas ex Louden) communities and is a common post-fire disturbance species. There is a lack of information regarding buffaloberry's ability to fix atmospheric N2 in Colorado forests. This study used the 15N natural abundance method in a survey of buffaloberry in north central Colorado to determine the percent of foliar N that buffaloberry derives from fixation (%Ndfa) and how fixation may be affected by local environmental factors. The mountain pine beetle (Dendroctonus ponderosae) epidemic is currently responsible for large losses in lodgepole pine forests. As the overstory canopies of lodge pole pine communities die off, there is an increase in available light in the understory. I investigated buffaloberry's response to light availability because with more photosynthetic activity, buffaloberry could potentially have more energy to expend in the energy intensive N2-fixation process. 59 plots (0.1-ha) were sampled in July 2009 and were distributed among Larimer, Jackson, and Grand counties in Colorado. Buffaloberry (15N: ‒0.63 /, N: 3.48%) had a 15N abundance closer to the atmospheric standard with high foliar %N content as compared to non-N2-fixing reference species (15N: ‒.29- ‒4.81 / N: 1.11-3.20%), indicating biological N2-fixation. I estimate a probable range of foliar %N derived from biological fixation as 60-100%. Buffaloberry (2.65%) also had higher % foliar N as compared to the reference species (1.50%) in the autumn, just before leaf abscission. There were no significant correlations between light availability and N2-fixation by buffaloberry suggesting that N2-fixation in buffaloberry may not benefit from an increase in light availability.
Open Access
Evaluating soil microbial community assembly to understand plant-soil diversity feedbacks
(Colorado State University. Libraries, 2022) Hoosein, Shabana, author; Paschke, Mark W., advisor; Trivedi, Pankaj, advisor; Stromberger, Mary, committee member; Busby, Ryan R., committee member; Egan, Cameron, committee member
To view the abstract, please see the full text of the document.
Open Access
Factors controlling long-term community development of a sagebrush steppe ecosystem
(Colorado State University. Libraries, 2010) Hoelzle, Timothy Brian, author; Paschke, Mark W., advisor; McLendon, Terry, committee member; Redente, Edward F., committee member; Stark, John M., committee member; Stromberger, Mary E., committee member
A study was established in 1984 in the Piceance Basin of northwest Colorado to examine how nutrient availability, soil organisms, and seed availability affect plant and microbial community development following disturbance. Initial results showed that increased nitrogen (N) availability and removal of soil organism limited plant community recovery, while decreased N availability and seeding with late seral species accelerated community development. Nutrient addition and immobilization treatments continued through 1999. Here, I examined how these treatments affected plant and microbial community composition 25 years after the initial disturbance. Supporting earlier findings, repeated N addition limited plant community succession, while phosphorus (P) addition had little effect. However, addition of N and P together worked synergistically to further retard successional recovery through the promotion of the invasive winter annual, Bromus tectorum L. Although nutrient additions resulted in differences in the rate of ecosystem development, few differences were observed in microbial biomass and composition, indicating that these treatments did not strongly affect these communities. Initial results showed that the rate of plant community development was accelerated by N immobilization through the addition of sucrose; however, I found that plant community composition was similar between these communities and those receiving N, indicating convergence in successional trajectories ten years after the cessation of treatments. Soil fungi, which often increase with community development, were higher in plots receiving the sucrose amendment. This suggests that, even though differences in successional development of the plant community were not found, succession in the belowground system was accelerated through sucrose additions. Although removal of soil organisms by fumigation initially slowed plant ecosystem recovery, these differences were no longer apparent 25 years later, illustrating that plant and microbial communities can recover from this type of disturbance. However, differences in successional trajectories were observed as a result of seed mix. Seeding with early seral species resulted in a community with significantly more exotic species and mid seral shrubs, while seeding with late seral species resulted in a community dominated by perennial grasses. This suggests that seed mix can alter successional trajectory, providing long-term evidence for the role of priority effects in community development.
Open Access
Plant selenium accumulation and the rhizosphere effect
(Colorado State University. Libraries, 2011) Alford, Élan Reine, author; Paschke, Mark W., advisor; Binkley, Dan, committee member; Borch, Thomas, committee member; Pilon-Smits, Elizabeth, committee member; Stromberger, Mary, committee member
To view the abstract, please see the full text of the document.
Open Access
Plant-soil feedbacks: a potential tool to improve management of invasive knapweeds
(Colorado State University. Libraries, 2011) Grant, Thomas A., III, author; Paschke, Mark W., advisor; Stromberger, Mary, committee member; Beck, K. George, committee member; Moore, John, committee member
To view the abstract, please see the full text of the document.
Open Access
Restoring plant and insect community diversity in a crested wheatgrass dominated area
(Colorado State University. Libraries, 2019) Abubaira, Mabruka H., author; Paschke, Mark W., advisor; Meiman, Paul, advisor; Brown, Cynthia S., committee member; Shahba, Mohamed A., committee member; Jonas, Jayne L., committee member
Changing climate and plant invasion are having negative impacts on biodiversity in rangeland ecosystems. Crested wheatgrass (Agropyron cristatum [L.] Gaertn.), a nonnative species, has been used to improve livestock forage on rangelands. However, this nonindigenous species can result in reduced native plant diversity. I conducted a study to determine the most successful native plants (southern, central, or northern US ecotypes) for use in restoration of crested wheatgrass stands and to examine if increased seed rain of forbs and shrubs will result in increased establishment of these life forms. In Fall 2012, I seeded a mix of native plants in a completely randomized design in Larimer County, CO. I tested 6 seed mix treatments containing southern, central, or northern US ecotypes: grass only, grass and forb, grass and shrub, grass, forb and shrub, or grass with bird perches to provide a natural source of seed rain, and unseeded controls. I sampled aerial cover of seeded and unseeded plants from 2013-2015. In each year, I observed native plants from southern areas had more cover than native plants from northern areas. Promoting seed rain via bird perches had no effect on forb and shrub cover. I found a high cover of non-native forbs in plots seeded with grass only. Establishing native plants in degraded rangelands is an important approach for restoring community diversity, and using ecotypes adapted to future conditions may help improve seeding success. Also, declines in plant species diversity led to decreases in insect diversity. In my study, I proposed that greater plant diversity would increase the number of herbivorous insects because insect communities depend on the availability of plants as basic resources for their growth. To examine the effects of plant richness on insect richness and abundance I sampled the insects by using three different techniques (drop trap, pitfall trap and pan trap) from the original restoration vegetation study. My results in this experimental study show that plant richness did not support the total number of insects. The total abundance of all insects did not differ significantly across treatments from data collected by pitfall trap and pan trap techniques. However, the order Homoptera was the most abundant group found in the verity of plant species treatment (n=15) from drop-trap data.
Open Access
Restoring two threatened Physaria species in the Piceance Basin of northwestern Colorado
(Colorado State University. Libraries, 2015) Victor, Sasha L., author; Paschke, Mark W., advisor; Vivanco, Jorge M., committee member; Dawson, Carol A., committee member
Physaria congesta and Physaria obcordata are rare plants endemic to the Piceance Basin of northwestern Colorado, USA. Since the Federal listing of both species in 1990, management efforts have focused largely on protecting critical habitat. However, this unique habitat is also a prime energy development area, necessitating additional measures to protect and restore both species. The overall objective of my research is to determine the best approach for establishing new populations of P. congesta and P. obcordata in suitable but unoccupied habitats in the Piceance Basin. To address this objective I used 3 methods: a soil feedback experiment, a field ecological survey, and a field establishment experiment. In recent years it has been shown that relative abundance of some species is strongly correlated with plant soil feedbacks and rare species can demonstrate strong negative feedbacks with pathogens from their own root systems (Klironomos 2002). Based on this theory I conducted a 12-week soil feedback study using field soil as inoculum collected from occupied and unoccupied suitable sites. I found no significant differences in plant biomass for either species when inoculated with soil from occupied or unoccupied habitats. To further investigate the differences between occupied and unoccupied sites I conducted a field ecological survey, building upon previous habitat suitability research, comparing plant cover, soil color, and soil/air temperature differential. I found significant differences between occupied and unoccupied sites for both species in multiple parameters (P. congesta = aspect, elevation, percent bare ground and rock, and soil color; P. obcordata = slope and soil color). Within occupied sites I found a negative correlation between P. congesta density and slope as well as a positive correlation between P. obcordata density with increased forb cover (< 5%) and decreased bare ground and rock cover (between 80 and 90%). The final phase of my research, which was delayed for a year due to legal issues, was to establish field plots, where I seeded and transplanted both species during fall 2014. Additional plants were transplanted during spring 2015. For each species three sites were located more than 600 meters from existing occupied habitat of the same species (Far Sites) and three within 600 meters (Near Sites). Initial germination and establishment rates, were collected spring 2015 and I found limited germination of seeded plots and moderate survival of fall transplants. Early trends show that P. obcordata is performing better than P. congesta and transplants are more successful than seeds. Within P. obcordata sites, far sites are performing better than near sites. During spring transplanting and monitoring I developed some initial suggestions to improve the success of transplanting including avoiding hard frosts (possibly by limiting transplanting to spring), ensuring that the soil is thoroughly tamped down during planting as well as planting flush to ground level to minimize impacts from wind, and finally watering at time of planting is essential and additional watering may be required in lower precipitation years. Long term monitoring is essential to understand the full efficacy establishment treatments as well as monitor these populations for reproduction, fecundity, response to disturbance, and population dynamics. Results from this research will assist land managers to make informed decisions regarding future conservation and restoration of these species.
Open Access
Using native annual plants to suppress weedy invasive species in post-fire habitats
(Colorado State University. Libraries, 2010) Herron, Christopher M., author; Paschke, Mark W., advisor; Rocca, Monique E., committee member; Brown, Cynthia Stokes, committee member; Meiman, Paul J., committee member
Increasing fire frequencies and uncharacteristic severe fires have created a need for improved restoration methods across rangelands in western North America. Traditional restoration seed mixtures of perennial mid- to late-seral plant species may not be suitable for intensely burned sites that have been returned to an early-seral condition. Under such conditions native annual plant species are likely to be more successful at competing with exotic annual plant species such as Bromus tectorum L. We used a field study in Colorado and Idaho, USA to test the hypothesis that native annual plant species are better suited to post-fire restoration efforts compared to perennial plant species that are commonly used in traditional seed mixtures. Replicated test plots at four post-fire sites were assigned one of four treatments (1) native annual seed mixture, (2) standard perennial seed mixture, (3) combination of annual and perennial, and (4) an unseeded control. Results suggest that there is potential for native annual plant species to be effective competitors with weedy exotic species in post-fire restoration scenarios.