Author: Raquel Henriques Flinker Publisher: ISBN: Category : Languages : en Pages : 160
Book Description
Increasing atmospheric carbon dioxide (CO2) leads to global warming. This can have several impacts on climate and on plant biodiversity, and has been the topic of many studies. The objective of this thesis was to understand the effects of higher atmospheric CO2 on soil moisture dynamics in the grasslands of central Minnesota using detailed hydrologic modeling to explain previous experimental observations at the BioCON site, a free-air CO2 enrichment experiment. The hydraulic properties and texture of soils collected from BioCON were determined in the laboratory through grainsize analysis and continuous evaporative drying to determine soil moisture retention curves and hydraulic conductivities. These results were used as input for numerical soil water flow and energy balance models. The models showed that vegetation presence and atmospheric CO2 concentrations significantly affected the soil moisture dynamics. Summer evapotranspiration (ET) had a higher variation for bare plots than for vegetated plots. This likely occurred because the vegetation provided a buffer against the variations in weather conditions. Vegetation not only retains part of the precipitation on its leaves, it also retains water in its structure and transpires while carrying out photosynthesis. Higher water content was also seen for the bare plots than for the vegetated soils. For some vegetated plots, there were differences between simulated and observed soil moisture. This could have been caused by a difference in plant composition and could suggest that different plant species can respond differently to varying CO2 atmospheric concentrations leading to different soil moisture dynamics. In addition to this, smaller ET values and higher soil water content values at vegetated elevated CO2 conditions than at ambient CO2 conditions were simulated. This was expected, as higher atmospheric CO2 is linked to higher plant water efficiency and larger biomass. For the simulations, higher values for stomatal resistance and higher plant and plant residue biomass were used. If increasing CO2 conditions in fact decreases ET, regional weather patterns could be affected as less ET could delay the speed that water flows through the water cycle.
Author: Raquel Henriques Flinker Publisher: ISBN: Category : Languages : en Pages : 160
Book Description
Increasing atmospheric carbon dioxide (CO2) leads to global warming. This can have several impacts on climate and on plant biodiversity, and has been the topic of many studies. The objective of this thesis was to understand the effects of higher atmospheric CO2 on soil moisture dynamics in the grasslands of central Minnesota using detailed hydrologic modeling to explain previous experimental observations at the BioCON site, a free-air CO2 enrichment experiment. The hydraulic properties and texture of soils collected from BioCON were determined in the laboratory through grainsize analysis and continuous evaporative drying to determine soil moisture retention curves and hydraulic conductivities. These results were used as input for numerical soil water flow and energy balance models. The models showed that vegetation presence and atmospheric CO2 concentrations significantly affected the soil moisture dynamics. Summer evapotranspiration (ET) had a higher variation for bare plots than for vegetated plots. This likely occurred because the vegetation provided a buffer against the variations in weather conditions. Vegetation not only retains part of the precipitation on its leaves, it also retains water in its structure and transpires while carrying out photosynthesis. Higher water content was also seen for the bare plots than for the vegetated soils. For some vegetated plots, there were differences between simulated and observed soil moisture. This could have been caused by a difference in plant composition and could suggest that different plant species can respond differently to varying CO2 atmospheric concentrations leading to different soil moisture dynamics. In addition to this, smaller ET values and higher soil water content values at vegetated elevated CO2 conditions than at ambient CO2 conditions were simulated. This was expected, as higher atmospheric CO2 is linked to higher plant water efficiency and larger biomass. For the simulations, higher values for stomatal resistance and higher plant and plant residue biomass were used. If increasing CO2 conditions in fact decreases ET, regional weather patterns could be affected as less ET could delay the speed that water flows through the water cycle.
Author: J. H. M. Thornley Publisher: Cabi ISBN: Category : Computers Languages : en Pages : 264
Book Description
The development of computer simulation models is an important growth area in both pure and applied ecology. The opportunity that mathematical models provide to integrate the components of an ecosystem, results in the ability to make quantitative predictions about the future behavior of that system, or of elements within it. This means that they are powerful tools with wide applications and enormous potential for increasing our understanding of natural systems and our ability to use them in a sustainable way. This book is, almost uniquely, a complete account of one such model, the Hurley Pasture Model, a dynamic, deterministic, mechanistic simulation model for grassland, which has been developed by the author over some 20 years, in collaboration with scientists at several centers. Firstly, the rationale and theoretical elements of this type of model are described. An overview of the Hurley grassland simulator and the derivation and construction of its plant, animal, soil and litter, water, and environment and management components is then given. Next, the model is evaluated by a series of long and short-term dynamic simulations and steady state responses, which demonstrate how predictions can be made about the effects of, for example, climate change or particular regimes of fertilizer application, grazing or cutting. This book will be of great value to grassland agronomists and modellers, crop physiologists and plant ecologists, and to students of ecology as a case study of a plant ecosystem model. It will also be of interest to other ecologists and environmentalists and those in the field of computer modelling and its applications.
Author: Xiaoming Kang Publisher: Frontiers Media SA ISBN: 2832547753 Category : Science Languages : en Pages : 320
Book Description
Forest and grassland ecosystems are the most important carbon sinks in terrestrial ecosystems. They can maintain or enhance carbon stocks and sinks in biomass, and play vital roles in mitigating climate change. China is taking action to achieve its carbon peak and carbon-neutral targets. Climate change, particularly the increase in the frequency, severity, and extent of drought, will affect the stability of the forest and grassland. How forests and grassland mitigate and adapt to climate change is still a challenge. Exploring the response of the forest and grassland to extreme climate events contributes to improving vegetation quality and enhancing the ability to respond to climate change.
Author: Anita C. Risch Publisher: ISBN: Category : Climatic changes Languages : en Pages : 13
Book Description
There is considerable interest in how ecosystems will respond to changes in precipitation. Alterations in rain and snowfall are expected to influence the spatio-temporal patterns of plant and soil processes that are controlled by soil moisture, and potentially, the amount of carbon (C) exchanged between the atmosphere and ecosystems. Because grasslands cover over one third of the terrestrial landscape, understanding controls on grassland C processes will be important to forecast how changes in precipitation regimes will influence the global C cycle. In this study we examined how irrigation affects carbon dioxide (CO2) fluxes in five widely variable grasslands of Yellowstone National Park during a year of approximately average growing season precipitation. We irrigated plots every 2 weeks with 25% of the monthly 30-year average of precipitation resulting in plots receiving approximately 150% of the usual growing season water in the form of rain and supplemented irrigation. Ecosystem CO2 fluxes were measured with a closed chamber-system once a month from May-September on irrigated and unirrigated plots in each grassland. Soil moisture was closely associated with CO2 fluxes and shoot biomass, and was between 1.6% and 11.5% higher at the irrigated plots (values from wettest to driest grassland) during times of measurements. When examining the effect of irrigation throughout the growing season (May?September) across sites, we found that water additions increased ecosystem CO2 fluxes at the two driest and the wettest sites, suggesting that these sites were water-limited during the climatically average precipitation conditions of the 2005 growing season. In contrast, no consistent responses to irrigation were detected at the two sites with intermediate soil moisture. Thus, the ecosystem CO2 fluxes at those sites were not water-limited, when considering their responses to supplemental water throughout the whole season. In contrast, when we explored how the effect of irrigation varied temporally, we found that irrigation increased ecosystem CO2 fluxes at all the sites late in the growing season (September). The spatial differences in the response of ecosystem CO2 fluxes to irrigation likely can be explained by site specific differences in soil and vegetation properties. The temporal effects likely were due to delayed plant senescence that promoted plant and soil activity later into the year. Our results suggest that in Yellowstone National Park, above-normal amounts of soil moisture will only stimulate CO2 fluxes across a portion of the ecosystem. Thus, depending on the topographic location, grassland CO2 fluxes can be water-limited or not. Such information is important to accurately predict how changes in precipitation/soil moisture will affect CO2 dynamics and how they may feed back to the global C cycle.
Author: Werner L. Kutsch Publisher: Cambridge University Press ISBN: 1139483161 Category : Technology & Engineering Languages : en Pages : 301
Book Description
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.
Author: William Williams Publisher: Springer Science & Business Media ISBN: 146125230X Category : Science Languages : en Pages : 217
Book Description
When Springer-Verlag undertook publication of this volume, two opportunities arose. The first was to bring together the significant findings ofthe interacting parts of a large field experiment on a whole ecosystem. Scientific specialists and the public are rightly concerned with large-scale impacts of human activity on landscapes and with the challenge of predicting subtle, long-range repercussions of air pollution. A fundamental issue is whether ecological systems like grasslands, which have evolved for several million years under stressful conditions such as variable climate and overgrazing, are more robust than other systems in tolerating new atmospheric impacts of pollution and toxicity. At what level, and when, will an extra geochemical input, like sulfur (Chapter 4), an essential nutrient for proteins and life processes, become an overload on these systems? Some grasses and grassland ecosystems seem fairly adaptable to burdens in addition to those of weather change and tissue removal. How can experts learn to project the future of the heartland of America and other grasslands of the world on the basis of only a few years of observation and control? The second opportunity addresses a broader aspect of the project that is of interest to many readers who are not concerned with details of physiology or food chains, or the overall productivity and variations of a single plant-animal-soil community.
Author: Rebecca Ryals Publisher: ISBN: Category : Languages : en Pages : 248
Book Description
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: Luo Yiqi Publisher: Elsevier ISBN: 0080463975 Category : Technology & Engineering Languages : en Pages : 334
Book Description
The global environment is constantly changing and our planet is getting warmer at an unprecedented rate. The study of the carbon cycle, and soil respiration, is a very active area of research internationally because of its relationship to climate change. It is crucial for our understanding of ecosystem functions from plot levels to global scales. Although a great deal of literature on soil respiration has been accumulated in the past several years, the material has not yet been synthesized into one place until now. This book synthesizes the already published research findings and presents the fundamentals of this subject. Including information on global carbon cycling, climate changes, ecosystem productivity, crop production, and soil fertility, this book will be of interest to scientists, researchers, and students across many disciplines. A key reference for the scientific community on global climate change, ecosystem studies, and soil ecology Describes the myriad ways that soils respire and how this activity influences the environment Covers a breadth of topics ranging from methodology to comparative analyses of different ecosystem types The first existing "treatise" on the subject
Author: Raquel Henriques Flinker
Author: Raquel Henriques Flinker
Author: J. H. M. Thornley
Author: Xiaoming Kang
Author: Anita C. Risch
Author: David J. Gibson
Author: Werner L. Kutsch
Author: William Williams
Author: Rebecca Ryals
Author: Luo Yiqi