Effects of Short-term and Long-term Natural Soil Warming Gradients on Plant Productivity, Carbon and Nitrogen Stocks of a Sub-arctic Grassland PDF Download
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Author: Katherine Vande Velde
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Languages : en
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Author: Katherine Vande Velde
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Languages : en
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Author: Stephanie Van Loock
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Languages : en
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In recent years, awareness of potential feedback mechanisms between global warming and primary productivity has increased. These feedbacks illustrate the importance of warming experiments, which have yielded important knowledge during the past decades. However, a thorough understanding on long-term warming effects on primary productivity and the effect of soil warming is still lacking. This study aimed to investigate short-term and long-term soil warming effects on vegetation biomass (proxy for primary productivity) and to explore the mechanisms behind the responses (direct temperature effects vs. indirect effects via warming-induced increased nitrogen (N) availability). The study took place at the ForHot research site, in the neighborhood of Hveragerði, Iceland. At this research site, subarctic grasslands on natural geothermal soil temperature gradients of different age are studied. One grassland had been warmed for approximately 8 years and was used to study short-term soil warming effects. The second grassland had been warmed for at least 50 years (probably for centuries), and was used to study long-term soil warming effects. Contrary to our expectations, soil warming decreased total vegetation biomass in both the short-term and the long-term warmed grassland. This was caused by a strong decrease of belowground biomass along the soil warming gradient in both grasslands presumably due to increased root turnover or direct temperature stress at high temperatures. Aboveground biomass was not affected by soil warming. The increasing shoot/root ratio with warming indicates that the aboveground productivity was not nutrient or water limited. Therefore, we hypothesize that the aboveground biomass was light limited, instead of temperature or nutrient limited. We conclude that long-term warming could decrease the carbon (C) sink capacity (primary production) of these northern grasslands by decreasing its belowground biomass stock if soil warming gives a reliable estimate of the effect of total ecosystem warming.
Author: Niel Verbrigghe
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Languages : en
Pages : 0
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Author: Rebecca Ryals
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Languages : en
Pages : 248
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Ecosystem management practices that sequester carbon (C) may play an important role in mitigating climate change. Grasslands managed for livestock (e.g., rangelands) constitute the largest land-use area globally. Critical components of the long-term sustainability of rangelands are the maintenance of net primary production (NPP) and soil organic carbon (C) pools. However, overgrazing, plant invasions, and climate change have led to significant C losses from many rangeland ecosystems. Thus, management practices may have considerable potential to restore or increase grassland C storage and help mitigate climate change. Practices that promote C sequestration may have valuable co-benefits, including increased forage production and improved soil water holding capacity. Despite the potential for C sequestration through management interventions, the question remains largely unexplored in grassland ecosystems. I used a combination of laboratory experiments, field manipulations, and modeling simulations to examine the effects of rangeland management practices on C sequestration and greenhouse gas emissions. The specific goals of this research were to 1) assess the immediate and carry-over effects of management practices on the net C balance and greenhouse gas emissions in grasslands amended with compost, 2) measure changes to soil C and N stocks following amendment, 3) investigate the long-term fate of compost C and net climate change mitigation potential, and 4) explore the extent of tradeoffs between C sequestration strategies and vegetation characteristics. In the first chapter, I conducted a three-year field manipulation replicated within and across valley and coastal grassland sites to determine the effects of a single application of composted organic matter amendment on net ecosystem C balance. Amendments increased C losses through soil respiration, and estimates of net C storage were sensitive to models of respiration partitioning of autotrophic and heterotrophic components. Over the three-year study, amendments increased C inputs by stimulating net primary production by 2.1 ± 0.8 at the coastal grassland and 4.7 ± 0.7 Mg C ha-1 at the valley grassland. Carbon gains through above- and belowground NPP significantly outweighed C losses, with the exception of a sandy textured soil at the coastal grasslands. Treatment effects persisted over the course of the study. Net ecosystem C storage increased by 25 to 70 % over three years, not including direct C inputs from the amendment. The purpose of chapter two was to further investigate changes to rangeland soil C and N stocks three years after a one-time application of composted organic material. Increases in bulk soil C, though often difficult to detect over short timeframes, were significant at the valley grassland study site. Physical fractionation of soil revealed greater amounts of C and N in the free and occluded light fractions by 3.31 ± 1.64 and 3.11 ± 1.08 Mg C/ha in the valley and coastal grassland, respectively. Analysis of the chemical composition of soil fractions by diffuse reflectance infrared Fourier transform (DRIFT) showed chemical protection and inclusion of compost C into the light fractions. The combination of physical and chemical analyses suggests that the newly incorporated C was physically protected and less available for decomposition. In the third chapter, I employed the ecosystem biogeochemical model, DAYCENT, to investigate the short (10 yr), medium (30 yr), and long-term (100 yr) climate change mitigation potential of compost amendments to grasslands. Climate change mitigation potential was estimated as the balance of total ecosystem C sequestration minus soil greenhouse gas emissions and indirect emissions of N2O via nitrate leaching. The model was parameterized using site-specific characteristics and validated with data from the three-year field manipulation. Model simulations included variations in the applications rate and C:N ratio of the composted material. Above- and belowground NPP and soil C pools increased under all amendment scenarios. The greatest increase of soil C occurred in the slow pool. Ecosystem C sequestration rates were highest under low C:N scenarios, but these scenarios also resulted in greater N2O fluxes. Single or short-term applications of compost resulted in positive climate change mitigation potential over 10 and 30-year time frames, despite slight offsets from increased greenhouse gas emissions. Finally, chapter four examined important tradeoffs between rangeland C sequestration activities and vegetation characteristics. I measured aboveground biomass, plant N content, vegetation communities, and the abundance of noxious weed species for four years following single management events of compost amendment, keyling plowing, and a combination of amendment and plowing. During the first year, plant N content and aboveground biomass was significantly higher in the amended plots and lower in the plowed plots. In the amended plots, forage quantity and quality increases were sustained over the four-year study. During spring grazing events, cows consumed more forage from amended plots without adversely increasing grazing impacts on residual biomass. Plant communities at both grasslands were relatively resistant to management events, however there were short-term declines in the abundance of a noxious annual grass at the valley grassland and increases in a noxious forb at the coastal grassland. Grassland management practices, such as the application of composted organic matter, have considerable potential to mitigate climate change while improving plant production, soil fertility, and diverting organic wastes from landfills. This research illustrates the potential for grassland management to sequester while explicitly considering impacts on greenhouse gas emissions, plant production, and vegetation communities over multiple time frames. Overall, my dissertation contributes toward a better understanding of the role of ecosystem management interventions in climate change mitigation.
Author: Yanfu Bai
Publisher: Frontiers Media SA
ISBN: 2832553109
Category : Science
Languages : en
Pages : 186
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Known as the “roof of the world,” the Tibetan Plateau is the highest and largest plateau on Earth. Tibetan Plateau hosts several mountain ecosystems characterized by high elevations, cold conditions, and a wide range in water availability. Its unique physical and geographical environment includes ecosystems typical for alpine regions, classified as alpine grasslands, which account for 50-70% of the total land area of the Tibetan plateau. Most of these grasslands contain fragile tundra-like environments which are seriously affected by anthropogenic modifications and whose restoration presents a challenge. These natural grassland types include alpine deserts, alpine steppes, alpine meadows, and alpine swamp meadows along precipitation gradients, as well as the transition types between them. Alpine grasslands remain subject to severe degradation by multiple factors, mainly overgrazing and climate warming. As a result, grasslands exhibit a decreased capacity to support biodiversity and complexity, and more generally, ecosystem functions. Therefore, these changes also affect social and recreational activities and restrict access to clean water and food by local communities.
Author: Richard V. Pouyat
Publisher: Springer Nature
ISBN: 3030452166
Category : Science
Languages : en
Pages : 306
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This open access book synthesizes leading-edge science and management information about forest and rangeland soils of the United States. It offers ways to better understand changing conditions and their impacts on soils, and explores directions that positively affect the future of forest and rangeland soil health. This book outlines soil processes and identifies the research needed to manage forest and rangeland soils in the United States. Chapters give an overview of the state of forest and rangeland soils research in the Nation, including multi-decadal programs (chapter 1), then summarizes various human-caused and natural impacts and their effects on soil carbon, hydrology, biogeochemistry, and biological diversity (chapters 2–5). Other chapters look at the effects of changing conditions on forest soils in wetland and urban settings (chapters 6–7). Impacts include: climate change, severe wildfires, invasive species, pests and diseases, pollution, and land use change. Chapter 8 considers approaches to maintaining or regaining forest and rangeland soil health in the face of these varied impacts. Mapping, monitoring, and data sharing are discussed in chapter 9 as ways to leverage scientific and human resources to address soil health at scales from the landscape to the individual parcel (monitoring networks, data sharing Web sites, and educational soils-centered programs are tabulated in appendix B). Chapter 10 highlights opportunities for deepening our understanding of soils and for sustaining long-term ecosystem health and appendix C summarizes research needs. Nine regional summaries (appendix A) offer a more detailed look at forest and rangeland soils in the United States and its Affiliates.
Author: Jordi Catalan
Publisher: Springer
ISBN: 3319559826
Category : Nature
Languages : en
Pages : 413
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This book provides case studies and general views of the main processes involved in the ecosystem shifts occurring in the high mountains and analyses the implications for nature conservation. Case studies from the Pyrenees are preponderant, with a comprehensive set of mountain ranges surrounded by highly populated lowland areas also being considered. The introductory and closing chapters will summarise the main challenges that nature conservation may face in mountain areas under the environmental shifting conditions. Further chapters put forward approaches from environmental geography, functional ecology, biogeography, and paleoenvironmental reconstructions. Organisms from microbes to large carnivores, and ecosystems from lakes to forest will be considered. This interdisciplinary book will appeal to researchers in mountain ecosystems, students and nature professionals. This book is open access under a CC BY license.
Author: Steward T.A. Pickett
Publisher: Elsevier
ISBN: 0080504957
Category : Science
Languages : en
Pages : 489
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Ecologists are aware of the importance of natural dynamics in ecosystems. Historically, the focus has been on the development in succession of equilibrium communities, which has generated an understanding of the composition and functioning of ecosystems. Recently, many have focused on the processes of disturbances and the evolutionary significance of such events. This shifted emphasis has inspired studies in diverse systems. The phrase "patch dynamics" (Thompson, 1978) describes their common focus. The Ecology of Natural Disturbance and Patch Dynamics brings together the findings and ideas of those studying varied systems, presenting a synthesis of diverse individual contributions.
Author: Robert Kenneth Connell
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Languages : en
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Plants are a major conduit through which carbon moves between the atmosphere and the terrestrial biosphere. The organic inputs from plants provide energy to soil microbes which fuels microbial extracellular enzyme production. Soil microbial activity determines the proportion of plant organic inputs that remains stored in soil as organic matter or is mineralized and released back into the atmosphere as carbon dioxide. Plant-soil interactions are, therefore, a critical driver of terrestrial carbon cycling. We live in an era of human-driven change which affects every aspect of ecosystem functioning, so it is critical to understand how different global change factors modulate the plant-soil interactions that influence carbon cycling. In this dissertation I focus on the effects of four specific global change factors on plant-soil interactions in a tallgrass prairie ecosystem: (1) land-use change (i.e., fire suppression and bison removal), (2) woody encroachment, (3) plant invasion, and (4) nutrient enrichment. The overall conclusion from my dissertation research is that all four of these global change factors alter plant-soil interactions in ways that change the storage or turnover of soil carbon. First, long-term fire suppression and/or bison exclusion increases soil C content over time. This change in soil C content is associated with an increase in woody plants in the case of fire suppression or an increase in the dominance of warm-season grasses in the case of bison exclusion under a frequent fire regime. Second, potential C mineralization rates under clonal woody shrubs is higher when the microbial community is decomposing proportionally more shrub-derived organic matter, suggesting that the rate of soil C flux may be dependent on how long the soil has been occupied by woody species. Third, the invasive grass Bromus inermis induces legacy effects on soil microbial community composition and soil organic matter (SOM) decomposition rates. These legacy effects persist for at least six months post-invasive grass removal. Finally, phosphorus fertilization stimulates the rate of SOM decomposition in soil undergoing woody encroachment, but nitrogen fertilization does not. Collectively, these results suggest that the effects of many global change factors on carbon cycling is dependent on spatiotemporal context and historical factors. Additionally, since each of the global change factors I studied affected carbon cycling independently, it will be important to study the combined effects of multiple global change factors acting simultaneously in order to better predict how carbon cycles through terrestrial ecosystems as the world continues to change.
Author: Werner L. Kutsch
Publisher: Cambridge University Press
ISBN: 1139483161
Category : Technology & Engineering
Languages : en
Pages : 301
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Carbon stored in soils represents the largest terrestrial carbon pool and factors affecting this will be vital in the understanding of future atmospheric CO2 concentrations. This book provides an integrated view on measuring and modeling soil carbon dynamics. Based on a broad range of in-depth contributions by leading scientists it gives an overview of current research concepts, developments and outlooks and introduces cutting-edge methodologies, ranging from questions of appropriate measurement design to the potential application of stable isotopes and molecular tools. It includes a standardised soil CO2 efflux protocol, aimed at data consistency and inter-site comparability and thus underpins a regional and global understanding of soil carbon dynamics. This book provides an important reference work for students and scientists interested in many aspects of soil ecology and biogeochemical cycles, policy makers, carbon traders and others concerned with the global carbon cycle.
