39 research outputs found
Microbial-mediated feedbacks of leaf litter on invasive plant growth and interspecific competition
No full textFeedbacks between plants and soil microbes can play an important role in competition between potential invaders and the resident community. However, the role of saprophytic soil microbes is poorly understood because research largely focuses on the role of specific soil-borne pathogens. Our aim was to examine the role of plant-saprophyte feedbacks in soil processes (decomposition and enzyme activities) and plant competition. We preconditioned a common soil in microcosms by decomposing litter of four species; two exotic invasive species (Microstegium vimineum and Berberis thunbergii) and two native species (Viburnum acerifolium and Vaccinium corymbosum). We then replaced the litter with either the same species' litter or a different species' litter on the preconditioned soil. We measured the effect of preconditioning on subsequent litter decomposition, microbial community structure (phospholipid fatty acids) and function (soil enzyme activities and decomposition). We then grew Berberis and Viburnum seedlings in preconditioned soils under intraspecific and interspecific competition to determine whether litter preconditioning had a feedback effect on competition. Changes in microbial community structure during preconditioning persisted through time and altered subsequent soil enzyme activities and litter decomposition. These changes also affected the growth rate of two shrub species, but because both shrubs grew best in soil that previously contained Berberis litter, competition between these species was not directly affected. Plant litter creates a legacy that influences the future structure of the microbial community even after that litter is gone. This legacy effect has functional consequences on decomposition and plant growth, and could be an important but under-appreciated factor in soil and plant community ecology. Further study is needed to determine how these consequences affect plant community composition and invasibility.National Science Foundation [DEB-0309047
Legacy effects overwhelm the short-term effects of exotic plant invasion and restoration on soil microbial community structure, enzyme activities, and nitrogen cycling
No full textPlant invasions can have substantial consequences for the soil ecosystem, altering microbial community structure and nutrient cycling. However, relatively little is known about what drives these changes, making it difficult to predict the effects of future invasions. In addition, because most studies compare soils from uninvaded areas to long-established dense invasions, little is known about the temporal dependence of invasion impacts. We experimentally manipulated forest understory vegetation in replicated sites dominated either by exotic Japanese barberry (Berberis thunbergii), native Viburnums, or native Vacciniums, so that each vegetation type was present in each site-type. We compared the short-term effect of vegetation changes to the lingering legacy effects of the previous vegetation type by measuring soil microbial community structure (phospholipid fatty acids) and function (extracellular enzymes and nitrogen mineralization). We also replaced the aboveground litter in half of each plot with an inert substitute to determine if changes in the soil microbial community were driven by aboveground or belowground plant inputs. We found that after 2 years, the microbial community structure and function was largely determined by the legacy effect of the previous vegetation type, and was not affected by the current vegetation. Aboveground litter removal had only weak effects, suggesting that changes in the soil microbial community and nutrient cycling were driven largely by belowground processes. These results suggest that changes in the soil following either invasion or restoration do not occur quickly, but rather exhibit long-lasting legacy effects from previous belowground plant inputs
The community-level and ecosystem-level consequences of feedbacks between the soil ecosystem and the plant community during forest understory invasion
No full textThis dissertation addresses the consequences of reciprocal interactions between the plant and the soil microbial communities, and how those interactions affect nutrient cycling and plant competition during exotic plant invasion. Each chapter is linked by the common theme of evaluating the importance of these feedbacks to the rate of plant invasion in the forest understory. In the first two chapters, I utilize microcosms to evaluate the importance of leaf litter inputs for plant-soil feedback. The first chapter demonstrates that leaf litter from native and exotic plants create divergent soil microbial communities, altering soil enzyme activities and nitrogen cycling, which in turn affects the growth of native and invasive plants. However, while this plant-soil interaction affects growth rate, it does not change the competitive hierarchy or the success of the invasive plant. The second chapter shows how the effect of an exotic species' leaf litter on soil microbes varies over a range of invasion severity. Using litter mixtures ranging from 0% to 100% exotic litter, I show that ecosystem-level effects of invasion on carbon and nitrogen cycling are linearly related to the exotic plant density, while community-level effects on soil microbes are non-linear and very sensitive to low levels of invasion. In the final chapters, I extend these results to examine whole-plant effects in more natural plant communities. The third chapter uses a large-scale field experiment to explore the temporal dynamics of invasion impacts. I show that the short-term impact of native and invasive plants on soil microbes is weak, while long-term effects are much stronger. However, after restoration of native plants, the legacy effect of invasion remains strong. Using experimental litter-removal, I also show that belowground plant litter more strongly influences the soil microbial community than aboveground litter. The fourth chapter examines how the diversity of the native community influences the invasion impact on soils. I show that while diversity has little direct effect, individual native plant species can influence how an exotic invasive shrub affects the soil ecosystem. Together, these results show that the importance of plant-soil feedbacks for exotic invasion is context- and scale-dependent, exhibiting nonlinear dynamics that depend on the native community and the degree of invasion, and vary in strength over time.Ph.D.Includes bibliographical referencesIncludes vitaby Kenneth John Elgersm
Evaluating vegetation response subsequent to CRP mid-contract management across the western United States: Draft Project Report
No full textIt is impossible to explicitly state the degree to which mid-contract management (MCM) impacts the benefits that CRP enrollments provide due to the size of the program and variety of management prescriptions. But it is well documented that all native grasslands evolved with some type of ecological disturbance and the relatively good health of the grassland correlates with its disturbance regime. Concomitantly, all grassland bird communities have habitat requirements that evolved in conjunction with disturbance (primarily grazing).
While natural-disturbance regimes may be desirable from an ecological prospective, dependence on natural disturbances to meet specific conservation objectives is unrealistic. Management policies are needed to encourage efforts to preserve and enhance grassland habitat by managing for heterogeneity while offsetting principal threats such as invasion of noxious plant species and woody vegetation. The accumulation of dead vegetation (litter), in the absence of management, greatly retards growth in the spring, prevents the emergence of some plants, reduces flowering, decreases productivity and promotes monocultures. Perpetuation of diversity in grass-species composition is a fundamental goal for trying to sustain desirable habitat for grassland-dependent wildlife. In the absence of natural disturbance, this goal is only accomplished through some form of prescribed management. And while some types of management are superior at replicating historic disturbances (grazing, burning), other forms of management (haying, mowing, disking) accomplish at least some level of necessary disturbance
The Effects of Varying Nitrogen Amounts on the Growth and Leaf Morphology of Cattail Species
No full textIn Iowa, there are three types of cattails (Typha spp.): Typha latifolia (broadleaf), Typha angustifolia (narrow leaf), and Typha x glauca. T. latifolia is native to Iowa, while T. angustifolia and T. x glauca are not native. Cattails are found in wetlands, highly productive ecosystems that provide many services such as water filtration and flood control.
However, Typha are opportunistic and invasive: if left uncontrolled, Typha grows rapidly by clonal reproduction, quickly dominating the ecosystem, lowering overall diversity and hurting the wetland’s conservation value. Being able to easily identify these taxa will improve the pace of future research.
The purpose of this study is to understand the effects of different nitrogen amounts on the growth and morphology of each Typha taxon. In order to achieve this, Typha was grown in 1.75-m mesocosms and in 25-cm pots with different amounts of fertilizer. Leaf length and width were measured, and a taxon was assigned based on those measurements. Leaves from these individuals were sampled, ground up for DNA extraction, purified, amplified by PCR, and sequenced. The data show how each taxon’s leaf height and width responds to differing nitrogen amounts
Calvin Theological Journal (Vol 48 No 1 - April 2013)
No full textArticles: The Imitation of Christ as Illumination for the Two Kingdoms Debate by John Bolt - 6 / Abraham had two sons : Augustine and the Allegory of Sarah and Hagar (Galatians 4:21–31) by Wendy Elgersma Helleman - 35 / Jonah 1:9—An Example of Elenctic Testimony by Carl J. Bosma - 65 / Missionary Ecclesiology in an Age of Individualization by Stefan Paas - 91 / From a Neo-Calvinistic to an Ecumenical Theology of Religions: The Development of the Theologia Religionum of Johannes Verkuyl by Rudolph Edward Stiemer - 107 / Pierre Viret on War and Peace by Robert D. Linder - 122 / Practicing the Kingdom: A Critical Appraisal of James K. A. Smith\u27s Desiring the Kingdom by Stephen Richard Turley - 131 / Loyal Orthodoxy: Christelijke Dogmatiek: Een Inleiding by G. Van den Brink and C. van der Kaai, reviewed by Eduardo J. Echeverria - 143 / Book Reviews - Theology and History: Boekestein, William, The Quest for Comfort: The Story of the Heidelberg Catechism, reviewed by Raymond A. Blacketer - 150 / Boulton, Matthew Myer, Life in God: John Calvin, Practical Formation, and the Future of Protestant Theology, reviewed by Andrew Hay - 151 / Bulgakov, Sergius, Icons and the Name of God; Bulgakov, Sergius, Jacob\u27s Ladder: On Angels, reviewed by Dylan Pahman - 153 / Douthat, Ross, Bad Religion: How We Became a Nation of Heretics, reviewed by Steve J. Van der Weele - 155 / Ellis, Brannon, Calvin, Classical Trinitarianism, and the Aseity of the Son, reviewed by Hans Boersma - 158 / Fesko, J. V., Beyond Calvin: Union with Christ and Justification in Early Modern Reformed Theology (1517–1700), reviewed by Ryan M. McGraw - 161 / Ha, Polly, English Presbyterianism, 1590–1640, reviewed by Kenneth J. Stewart - 163 / Kapic, Kelly M., A Little Book for New Theologians: Why and How to Study Theology, reviewed by Mary L. Vanden Berg - 165 / Letham, Robert, Union with Christ: In Scripture, History, and Theology, reviewed by Mary L. Vanden Berg - 166 / Long, Kimberly Bracken, The Eucharistic Theology of the American Holy Fairs, reviewed by Kenneth J. Stewart - 169 / Mattson, Brian G., Restored to Our Destiny: Eschatology and the Image of God in Herman Bavinck\u27s Reformed Dogmatics; Eglinton, James P., Trinity and Organism: Towards a New Reading of Herman Bavinck\u27s Organic Motif, reviewed by John Bolt - 171 / Watt, Isabella M., and Jeffrey R. Watt, eds., Registres du Consistoire de Geneve au Temps de Calvin, Tome VI (19 fevrier 1551–4 fevrier 1552), reviewed by Karen E. Spierling - 175 / Church and Mission: Lofton, Kathryn, Oprah: The Gospel of an Icon, reviewed by Kyle Dielemann - 177 / Meyerink, Dorothy Dickens, Ministry among the Maya: A Missionary Memoir, reviewed by Paul J. Bergsma - 179 / Romanowski, William D., Reforming Hollywood: How American Protestants Fought for Freedom at the Movies, reviewed by Josh Larsen - 181https://digitalcommons.calvin.edu/ctj/1094/thumbnail.jp
Linear and non-linear impacts of a non-native plant invasion on soil microbial community structure and function
No full textSoil Organic Carbon Accumulation in Restored Native Prairies Over Time [Poster]
No full textWith the recent focus on the causes and effects of climate change, the relationship between agriculture and climate change has become an important concern. Conventional farming maximizes crop production at the expense of ecosystem services like soil carbon storage. As the human population grows, it is vital to develop practices that balance crop production and ecosystem services.
We investigated organic carbon accumulation in restored prairie soil over the course of a decade. Our goal was to determine how organic carbon levels and soil bulk density changed over time, and how that change was influenced by species diversity and soil depth. We hypothesized that more organic carbon would be stored in soil over time, and bulk density would decrease, both of which we found to be true. We also hypothesized that the amount of organic carbon stored would increase with greater species diversity (1-species, and 5-, 16-, and 32-species mixes) and it would decrease with soil depth. Our results showed us that species diversity has no noticeable effect on organic carbon levels, with the 5-species mix being the exception, as it stored very low levels of organic carbon. In both soil depths (0-7.5 cm and 7.5-15.0 cm), bulk density increased the first 5 years, then decreased drastically over the next 6 years, but when we compared 0-7.5 cm and 7.5-15.0 cm depths with each other, we found an overall decrease. We concluded that organic carbon accumulation increases over time in restored prairie soil regardless of species diversity or soil depth
Density and diversity of bees in the midwestern agricultural landscape: Influence of surrounding agricultural land use and biofuel candidate crops
No full textRecent trends in land management practices have led to dramatic population decline in bees and other insect pollinators (Cameron et al. 2011). Concerns about “Colony Collapse Disorder” in domestic honeybees, for example, have received widespread high-profile attention in the scientific community. While concerns have centered mainly on the domestic honeybee, native bees also provide indispensable, cost-free pollination services to crops production. Despite the value of native bee species, little is known about them in the Midwest region, and recent studies suggest their populations may be in decline specifically due to a lack of native vegetation in this highly agricultural landscape. Vegetable farms and lands managed for cellulosic biofuels have the potential to provide usable habitat, but their utility is not well understood
