Sensitivity Of Soil Organic Matter In Cryoturbated Arctic Soils Against Permafrost Thaw
DOWNLOAD
Download Sensitivity Of Soil Organic Matter In Cryoturbated Arctic Soils Against Permafrost Thaw PDF/ePub or read online books in Mobi eBooks. Click Download or Read Online button to get Sensitivity Of Soil Organic Matter In Cryoturbated Arctic Soils Against Permafrost Thaw book now. This website allows unlimited access to, at the time of writing, more than 1.5 million titles, including hundreds of thousands of titles in various foreign languages. If the content not found or just blank you must refresh this page
Sensitivity Of Soil Organic Matter In Cryoturbated Arctic Soils Against Permafrost Thaw
DOWNLOAD
Author : Norman Gentsch
language : en
Publisher:
Release Date : 2017
Sensitivity Of Soil Organic Matter In Cryoturbated Arctic Soils Against Permafrost Thaw written by Norman Gentsch and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Permafrost soils, soil organic matter, climate change. - Permafrostboden, organische Bodensubstanz, Klimawandel
Size Fractionation And Characterization Of Cryoturbated Soil Organic Matter In Arctic Tundra Alaska
DOWNLOAD
Author : Chunhao Xu
language : en
Publisher:
Release Date : 2005
Size Fractionation And Characterization Of Cryoturbated Soil Organic Matter In Arctic Tundra Alaska written by Chunhao Xu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with Carbon cycle (Biogeochemistry) categories.
"Recent studies indicated a second layer of organic matter often accumulates in the lower active layer and upper permafrost in arctic tundra soils due to cryoturbation. The objective of this study is to characterize cryoturbated organic matter by the combination of physical size-fractionation approaches with modern analytical techniques. The results of elemental composition (C, N), stable isotope (13C, 15N), radiocarbon age (14C), and molecular fingerprints (Py-GC/MS) analysis indicated cryoturbated organic matters are little humified and highly bioavailable. SOM (soil organic matter) associated with fine sand size particles was considered to be the organic carbon pool most sensitive to the changing climate. Clay minerals stabilize less humifed organic matter than those in temperate and tropical soils. The bioavailable soluble organics extracted from cryoturbated organic matter were found to have significant long-term accumulated effects on carbon cycling. The similar molecular compositions between cryoturbated and surface organic matter suggest vegetation covers haven't changed since the early Holocene. Furthermore, the quality of SOM in moist acidic tundra is higher than that of wet nonacidic tundra. With the deepening active layer followed by thawing permafrost, cryoturbated organic matter could reenter the biogeochemical cycles in the Arctic, resulting in a positive feedback to climate change"--Leaf iii.
Permafrost Soils
DOWNLOAD
Author : Rosa Margesin
language : en
Publisher: Springer Science & Business Media
Release Date : 2008-10-31
Permafrost Soils written by Rosa Margesin and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008-10-31 with Science categories.
Most of the Earth’s biosphere is characterized by low temperatures. Vast areas (>20%) of the soil ecosystem are permanently frozen or are unfrozen for only a few weeks in summer. Permafrost regions occur at high latitudes and also at high ele- tions; a significant part of the global permafrost area is represented by mountains. Permafrost soils are of global interest, since a significant increase in temperature is predicted for polar regions. Global warming will have a great impact on these soils, especially in northern regions, since they contain large amounts of organic carbon and act as carbon sinks, and a temperature increase will result in a release of carbon into the atmosphere. Additionally, the intensified release of the clima- relevant tracer gas methane represents a potential environmental harzard. Significant numbers of viable microorganisms, including bacteria, archaea, p- totrophic cyanobacteria and green algae, fungi and protozoa, are present in per- frost, and the characteristics of these microorganisms reflect the unique and extreme conditions of the permafrost environment. Remarkably, these microorg- isms have been reported to be metabolically active at subzero temperatures, even down to ?20°C.
Cryosols
DOWNLOAD
Author : John Kimble
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-03-14
Cryosols written by John Kimble and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-03-14 with Nature categories.
Cryosols – permafrost – occupy a unique part of the earth and have properties greatly different from other soils. They also occur where the greatest impact of global warming is predicted. This is the first book bring together the leading researchers in the area of permafrost soils to produce a review of the geography, cryogenic soil forming processes, ecological processes, classification and use of soils that are affected by permafrost.
Permafrost Organic Matter Quality And Biolability In The Vault Lake Thermokarst Environment Interior Alaska Usa
DOWNLOAD
Author : Joanne K. Heslop
language : en
Publisher:
Release Date : 2017
Permafrost Organic Matter Quality And Biolability In The Vault Lake Thermokarst Environment Interior Alaska Usa written by Joanne K. Heslop and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Greenhouse gases categories.
Warming and thawing of permafrost soils removes a major barrier to soil organic carbon (SOC) mineralization, leading to the mobilization and microbial degradation of previously frozen, inactive permafrost organic carbon (OC) into the greenhouse gases carbon dioxide (CO2) and methane (CH4). Many thermokarst (thaw) lakes formed in permafrost-dominated landscapes have high rates of CO2 and CH4 emission; however, the composition and biodegradability of the thawed permafrost OC as they relate to the relative magnitudes of anaerobic OC mineralization at different depths throughout the vertical profile of a thermokarst-lake talik system have, to my knowledge, never been measured. My research examined OC composition and mineralization potentials at the Vault Creek (VC) permafrost tunnel and Vault Lake, located 20 km north of Fairbanks, Alaska, USA, to better constrain these uncertainties. I found that, in a 590-cm long sediment core collected from the center of Vault Lake, whole-column CH4 production is dominated by methanogenesis in the organic-rich mud facies, which occurred in the surface 0 to 152 cm. CH4 production potential rates positively associated with substrate availability (carbon and nitrogen concentrations) and the relative abundances of terrestrially-derived organic matter compounds (alkanes, alkenes, lignin products, and phenols and phenolic precursors), measured using pyrolysis-gas chromatography-mass spectrometry. Temperature sensitivity analyses conducted on a subset of samples from the Vault Lake sediment core suggest century-scale time since permafrost thaw affects temperature sensitivities of CH4 production. Freshly-thawed taberite sediments at the base of the talik (thaw bulb) were most sensitive to warming at lower incubation temperatures (0 °C to 3 °C), while the overlying taberite sediments thawed in situ longer periods of time (up to 400 years based on radiocarbon dating) did not experience statistically significant increases in CH4 production until higher incubation temperatures (10 °C to 25 °C). Finally, using anaerobic incubations and ultrahigh-resolution mass spectrometry of water-extractable organic matter along a 12-m yedoma profile in the VC permafrost tunnel, I show that yedoma OC biolability increases with depth as indicated by increasing proportions of aliphatics and peptides (reduced, high H/C compounds). These compounds also positively correlated with anaerobic CO2 and CH4 production, and corresponded to high proportions (5.6% to 118 %) of OC mineralization rates in incubations. This suggests that as yedoma permafrost thaws beneath a thermokarst lake greenhouse gas production potentials may increase with thaw depth.
Temperature Sensitivity Of Soil Organic Matter Pools
DOWNLOAD
Author : Michelle Haddix
language : en
Publisher:
Release Date : 2007
Temperature Sensitivity Of Soil Organic Matter Pools written by Michelle Haddix and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Global temperature changes categories.
Organic Matter In Permafrost Affected Soils As Affected By Soil Forming Processes And Vegetation In The Arctic And Antarctica
DOWNLOAD
Author : Isabel Prater
language : en
Publisher:
Release Date : 2023
Organic Matter In Permafrost Affected Soils As Affected By Soil Forming Processes And Vegetation In The Arctic And Antarctica written by Isabel Prater and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
What S The Holdup
DOWNLOAD
Author : Ruth Whittington
language : en
Publisher:
Release Date : 2019
What S The Holdup written by Ruth Whittington and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with Soil enzymology categories.
Arctic ecosystems contain globally important terrestrial carbon stocks, and their temperatures are rising at twice global rates. While increasing temperatures lead to faster decomposition and carbon mineralization rates, predicting the magnitude and future patterns of soil respiration is difficult due to multiple interacting direct and indirect effects. In particular, we lack mechanistic data on how low temperatures impact extracellular enzyme activities and thereby determine carbon supply rates to respiration. For this research, I performed two laboratory soil incubations designed to measure the temperature responses of enzymes catalyzing the terminal steps in Arctic tundra soil organic matter depolymerization. These experiments were designed to first characterize microbial activity responses to temperature based on cumulative carbon loss, and then to identify how substrate and nutrient availability mediate indirect temperature responses. In the first experiment, tundra soils were incubated across a temperature gradient from 4 - 20 °C and subsequently harvested at four time points at comparable levels of cumulative carbon loss. Comparing temperature effects on respiration rates as they changed with greater substrate depletion, respiration temperature sensitivity declined over time, likely due to declining substrate availability at higher temperatures. In contrast, enzyme temperature sensitivity increased over time, an apparent consequence of increased enzyme production at higher temperatures. These results indicate that carbon flow from depolymerization may not be high enough to sustain microbial activity below 10 °C and may explain observations of unexpectedly high increases in soil respiration with temperature in this range. In a second experiment, labile carbon was added with and without nutrients to tundra soils incubated at 8 and 16 °C and subsequently harvested at three points based on cumulative carbon loss from control soils. Respiration temperature sensitivity increased following labile carbon addition, indicating low substrate availability suppressed temperature responses from control soils. Temperature limitations to enzyme production persisted across all treatments, suggesting limitations to enzyme production may be due to lower microbial demand at low temperatures. Overall, results from this research demonstrate a number of indirect temperature effects on enzyme production and carbon availability that are currently unaccounted for in predictive Earth system models. Furthermore, they suggest that both enzyme production and activity are likely to increase as Arctic soils warm, two mechanisms by which temperature rise may increase carbon transfer from tundra soils to the atmosphere.
Changes To Soil And Sedimentary Organic Matter Composition With Permafrost Active Layer Detachments In A Canadian High Arctic Watershed
DOWNLOAD
Author : David Michael Grewer
language : en
Publisher:
Release Date : 2017
Changes To Soil And Sedimentary Organic Matter Composition With Permafrost Active Layer Detachments In A Canadian High Arctic Watershed written by David Michael Grewer and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
The vast reservoir of organic matter (OM) locked up in Arctic permafrost may become vulnerable to degradation with increased thawing. In recent years, higher than average Arctic temperatures have increased the frequency of abrupt permafrost thawing events. On sloped terrain, deeper seasonal thawing of permafrost soils can initiate landslide-like events called active layer detachments (ALDs) which can release large amounts of previously unavailable carbon into the surrounding environment. Once exposed, more easily degraded permafrost-derived OM may be transported and mineralized through hydrological networks, altering biogeochemical cycles both locally and globally. It is therefore important to investigate the environmental fate of permafrost-derived OM following release by ALDs. Several complementary methods were used to investigate soil and sedimentary OM composition from an ALD-impacted High Arctic watershed, including: biomarker analyses via gas chromatography-mass spectrometry (solvent extractable compounds, base hydrolysable products, CuO oxidation products, phospholipid fatty acids), solid-state 13C nuclear magnetic resonance (NMR) spectroscopy, and radiocarbon analysis using accelerator mass spectrometry. Samples collected from the watershed represented three distinct environments: soils, fluvial sediments, and lacustrine sediments. Soil OM composition of depth profiles from upslope and downslope regions of the disturbance were compared. Lower amounts of labile OM upslope, suggesting increased erosion, contrasted with higher amounts downslope indicative of the accumulation of OM. Additionally, labile OM observed in subterranean soil downslope indicates storage of more easily degraded material in deep permafrost. Fluvial sedimentary OM composition downstream of the disturbance was investigated to characterize potential shifts in OM composition resulting from ALD inputs. In addition, downstream translocation of ALD inputs over time was determined when comparing samples from 2011, 2013, and 2014. OM composition in areas along the river receiving ALD inputs also shifted from permafrost-derived biomarkers toward more contemporary aquatic-derived inputs over time. OM composition from recent lacustrine sediments contained older, more persistent compounds suggesting that the labile OM released by ALDs likely undergoes degradation before reaching the lake. Overall, this thesis reveals the ongoing shifts in the OM composition of ALD-impacted Arctic landscapes and contributes to the growing body of evidence suggesting enhanced losses of labile permafrost-derived carbon with future warming and climate change.
Subsurface Controls On Carbon Dynamics In A Changing Arctic Ecosystem
DOWNLOAD
Author : Lydia Smith Vaughn
language : en
Publisher:
Release Date : 2017
Subsurface Controls On Carbon Dynamics In A Changing Arctic Ecosystem written by Lydia Smith Vaughn and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
With climate change in the Arctic, temperatures are expected to rise at twice the rate as in temperate latitudes. This rapid change has the potential to disrupt local ecosystems and feed back to the global climate as frozen soils thaw and warm. Large stocks of carbon have accumulated in Arctic soils, protected from decomposition by cold, wet, and frozen conditions. With warming and thawing due to climate change, decomposition of this carbon is expected to increase, releasing it to the atmosphere as the greenhouse gases CO2 and methane. While a number of modeling efforts have attempted to quantify this potential feedback, the future Arctic carbon balance remains unknown due to uncertain mechanisms stabilizing soil carbon and complex interactions between vegetation and soils. In studies based in Barrow, Alaska, I address three sources of this uncertainty: (1) the magnitude of methane emissions following soil thaw, (2) interactions between plants, soil carbon, and microbial decomposers, and (3) the sensitivity of soil carbon cycling changes in microclimate. First, I ask how methane formation, consumption within the soil, and net emission to the atmosphere may change with soil thaw in the Arctic. Loss of permafrost (perennially frozen ground) can lead to large-scale landscape changes, redistributing water and soil. Such physical changes can strongly influence emissions of methane, a greenhouse gas roughly 25 times as potent as CO2, whose future emission rates are highly uncertain. Combining field measurements with statistical modeling, I assess soil methane emissions and microbial methane processes (production and consumption) across a gradient of permafrost thaw. In contrast with many previous studies, I find that more degraded sites have lower methane emissions, a different primary methanogenic pathway, and greater methane oxidation than intact permafrost sites. These differences are greater than soil moisture or temperature data can explain. Additional microtopographic controls accounting for these observations may include differences in water flow and vegetation between intact and degraded polygons. Second, I ask how changes in plant activity due to climate change may influence the rate of soil carbon decomposition (the priming effect), through interactions between plant roots, microbial decomposers, and soil carbon compounds. In a two-year field experiment, I simulate increased plant root activity and measure its influence on soil carbon decomposition, plant CO2 uptake, mineral nitrogen availability, and microbial communities. I find no measurable relationship between substrate additions and soil organic matter decomposition, nutrient supply, or microbial population size. Treatment-level differences in primary production, however, indicate possible longer-term interactions between vegetation and decomposition. The absence of a measurable priming effect contrasts with numerous published reports documenting a positive priming effect under tightly controlled conditions. This difference may be due to high background variability in ecosystem respiration, a property of this in situ experiment. This chapter is one of the first studies evaluating this plant-soil interaction in a field experimental context, with a representative degree of environmental variability. Third, I ask how decomposition rates of fast-cycling and slow-cycling soil carbon may be influenced by microclimatic changes. The rate of soil carbon turnover and its sensitivity to environmental variables such as temperature and oxygen availability are both highly uncertain and highly influential for model predictions of the global carbon cycle. In two laboratory incubations, I use natural abundance radiocarbon measurements of CO2 and soil organic matter to determine how fast-cycling and slow-cycling carbon pools respond to temperature changes and transitions between anaerobic and aerobic conditions. Using a novel analytical approach, I find that fast- and slow-cycling carbon pools from these Barrow, Alaska soils have comparable temperature sensitivities, with decomposition from both pools increasing by ~40 % for a 5°C temperature increase. Similarly, decomposition rates were highly sensitive to aerobic vs. anaerobic conditions, with no significant difference in sensitivity between pools. Radiocarbon contents of CO2 and soil organic matter indicate that ancient, slow-cycling carbon is sensitive to decomposition under soil temperature increases and water table changes.