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Mark W. Williams - One of the best experts on this subject based on the ideXlab platform.
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evidence for non steady state carbon emissions from snow scoured Alpine Tundra
Nature Communications, 2019Co-Authors: John F. Knowles, Peter D. Blanken, Corey R. Lawrence, Mark W. WilliamsAbstract:High-latitude warming is capable of accelerating permafrost degradation and the decomposition of previously frozen carbon. The existence of an analogous high-altitude feedback, however, has yet to be directly evaluated. We address this knowledge gap by coupling a radiocarbon-based model to 7 years (2008–2014) of continuous eddy covariance data from a snow-scoured Alpine Tundra meadow in Colorado, USA, where solifluction lobes are associated with discontinuous permafrost. On average, the ecosystem was a net annual source of 232 ± 54 g C m−2 (mean ± 1 standard deviation) to the atmosphere, and respiration of relatively radiocarbon-depleted (i.e., older) substrate contributes to carbon emissions during the winter. Given that Alpine soils with permafrost occupy 3.6 × 106 km2 land area and are estimated to contain 66.3 Pg of soil organic carbon (4.5% of the global pool), this scenario has global implications for the mountain carbon balance and corresponding resource allocation to lower elevations. The potential contribution of high altitude permafrost as a climate feedback is unknown. Here the authors show seven years of sustained carbon emissions from snow-scoured Alpine Tundra including respiration of older carbon substrate from solifluction lobes associated with permafrost during the winter.
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Evidence for non-steady-state carbon emissions from snow-scoured Alpine Tundra
Nature Publishing Group, 2019Co-Authors: John F. Knowles, Peter D. Blanken, Corey R. Lawrence, Mark W. WilliamsAbstract:The potential contribution of high altitude permafrost as a climate feedback is unknown. Here the authors show seven years of sustained carbon emissions from snow-scoured Alpine Tundra including respiration of older carbon substrate from solifluction lobes associated with permafrost during the winter
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contribution of deeper soil horizons to n and c cycling during the snow free season in Alpine Tundra nw italy
Catena, 2017Co-Authors: Andrea Magnani, Mark W. Williams, Davide Viglietti, Raffaella Balestrini, Michele FreppazAbstract:Abstract In Alpine Tundra the contribution of subsurface soil horizons to N and C cycling, their intraseasonal variability and soil/water interaction in the snow-free season have been poorly studied. The hypothesis that subsoil pedoclimatic factors (soil moisture and soil temperature) and nutrients (extractable N-NH4+, N-NO3−, DON, DOC, Nmicr and Cmicr) can differ significantly from those of the topsoil was tested for 3 snow-free seasons at 3 study sites (site 1, 3 and 5) in the Alpine Tundra of the NW Italian Alps. In addition, the intraseasonal variability of both topsoil and subsoil extractable N and C forms was checked monthly from July to October, and they were related to those measured in the surface water of an Alpine lake (Cimalegna Lake). The soil moisture did not show significant differences between topsoil and subsoil, with the exception of site 5, and was strictly correlated with the N and C forms studied at both soil depths, except for N-NO3−. The soil temperature was always slightly higher in the topsoil than in the subsoil, due to the incident solar irradiance, and was positively correlated with topsoil DON and Cmicr. At all study sites, N-NH4+ and N-NO3− showed no significant differences between topsoil and subsoil, while subsoil DON, DOC, Nmicr and Cmicr significantly differed from those in the topsoil, especially at site 5. Only N-NO3− had a significant intraseasonal variability reaching the highest values in October at both soil depths, mainly due to the end of the plants growing season. The temporal variation of N-NO3− concentration observed in the lake strictly reflects the temporal changes occurred in the soils underling the fundamental role of soil biocenosis in limiting leaching losses of nitrates.
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interannual variability of soil n and c forms in response to snow cover duration and pedoclimatic conditions in Alpine Tundra northwest italy
Arctic Antarctic and Alpine Research, 2017Co-Authors: Andrea Magnani, Mark W. Williams, Davide Viglietti, Danilo Godone, Raffaella Balestrini, Michele FreppazAbstract:ABSTRACT In Alpine Tundra the influence of snow-cover duration (SCD) and pedoclimatic conditions on soil nutrient forms during the growing season has received little attention. The hypothesis that SCD influences the soil temperature, which in turn can affect the annual changes in topsoil nitrogen (N) and carbon (C) forms, was tested for five growing seasons at three study sites in the Alpine Tundra of the NW Italian Alps. Among the pedoclimatic conditions studied (soil temperature, soil moisture, and number of freeze/thaw cycles), the mean soil temperature of the growing season was inversely correlated with the SCD (p < 0.01), which ranged from 216 to 272 days. Independently from the soil characteristics (e.g., degree of evolution), the microbial carbon (Cmicr) of the growing season was inversely correlated with the SCD and the mean soil temperature of the snow-covered season, suggesting the consumption of soil resources made by the Cmicr under the snowpack. During the growing season ammonium (N-NH4+), di...
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energy and surface moisture seasonally limit evaporation and sublimation from snow free Alpine Tundra
Agricultural and Forest Meteorology, 2012Co-Authors: John F. Knowles, Peter D. Blanken, Mark W. Williams, Kurt ChowanskiAbstract:This study highlights the importance of landscape position and resultant snow accumulation to the hydrologic balance of snow-free Alpine Tundra, and suggests that modeling studies must account for seasonally dissimilar partitioning of the energy balance in order to accurately predict evaporation and/or sublimation. The eddy covariance method was used to measure the surface energy balance above high-elevation (3502 m above sea level) Alpine Tundra at Niwot Ridge, CO, over 3 years from 2007 to 2009. During the winter the site was characterized by wind scour, with little snow accumulation. Two co-located towers afforded the opportunity to constrain the influence of complex mountain topography on measurement uncertainty, and overall errors were comparable to other FLUXNET sites. Random measurement uncertainty for the turbulent fluxes was approximately 10% of midday summertime values. The 0.5-h mean energy balance closure was 81% over the entire measurement period, and improved to 91% during the summer when the magnitude of the turbulent fluxes was larger. In spite of 955 mm mean annual precipitation, the 24-h mean evaporative fraction was 0.39, typical of dry grassland or rangeland ecosystems. These low values were attributed to rapid, efficient removal of snow by prevailing windy conditions throughout the winter. During the summer when rainfall provided moisture, evaporation was principally limited by available energy. Overall, an average of 39% of annual precipitation was evaporated or sublimated back to the atmosphere. We conclude that the annual distribution of precipitation is an essential control on evaporation and sublimation from this ecosystem.
Steven K Schmidt - One of the best experts on this subject based on the ideXlab platform.
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the effects of chronic nitrogen fertilization on Alpine Tundra soil microbial communities implications for carbon and nitrogen cycling
Environmental Microbiology, 2008Co-Authors: Diana R Nemergut, William D. Bowman, Jason C. Neff, Alan R Townsend, Sarah R Sattin, Kristen R Freeman, Noah Fierer, Christopher W Schadt, Michael N Weintraub, Steven K SchmidtAbstract:Summary Many studies have shown that changes in nitrogen (N) availability affect primary productivity in a variety of terrestrial systems, but less is known about the effects of the changing N cycle on soil organic matter (SOM) decomposition. We used a variety of techniques to examine the effects of chronic N amendments on SOM chemistry and microbial community structure and function in an Alpine Tundra soil. We collected surface soil (0–5 cm) samples from five control and five long-term N-amended plots established and maintained at the Niwot Ridge Longterm Ecological Research (LTER) site. Samples were bulked by treatment and all analyses were conducted on composite samples. The fungal community shifted in response to N amendments, with a decrease in the relative abundance of basidiomycetes. Bacterial community composition also shifted in the fertilized soil, with increases in the relative abundance of sequences related to the Bacteroidetes and Gemmatimonadetes, and decreases in the relative abundance of the Verrucomicrobia. We did not uncover any bacterial sequences that were closely related to known nitrifiers in either soil, but sequences related to archaeal nitrifiers were found in control soils. The ratio of fungi to bacteria did not change in the N-amended soils, but the ratio of archaea to bacteria dropped from 20% to less than 1% in the N-amended plots. Comparisons of aliphatic and aromatic carbon compounds, two broad categories of soil carbon compounds, revealed no between treatment differences. However, G-lignins were found in higher relative abundance in the fertilized soils, while proteins were detected in lower relative abundance. Finally, the activities of two soil enzymes involved in N cycling changed in response to chronic N amendments. These results suggest that chronic N fertilization induces significant shifts in soil carbon dynamics that correspond to shifts in microbial community structure and function.
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microbial diversity in Alpine Tundra wet meadow soil novel chloroflexi from a cold water saturated environment
Environmental Microbiology, 2006Co-Authors: Elizabeth K Costello, Steven K SchmidtAbstract:Summary Cold, water-saturated soils play important biogeochemical roles, yet almost nothing is known about the identity and habitat of microbes active under such conditions. We investigated the yearround microenvironment of an Alpine Tundra wet meadow soil in the Colorado Rocky Mountains, focusing on the biogeochemistry and microbial diversity of spring snowmelt ‐ a dynamic time for Alpine ecosystems. In situ measurements revealed spring and autumn periods of long-term temperature stability near 0 ! C, and that deeper soil (30 cm) was more stable than surface soil, with more moderate summers and winters, and longer isothermal phases. The soil was saturated and water availability was limited by freezing rather than drying. Analyses of bioavailable redox species showed a shift from Mn reduction to net Fe reduction at 2‐3 cm depth, elevated SO 4 2‐ and
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microbial diversity in Alpine Tundra wet meadow soil novel chloroflexi from a cold water saturated environment
Environmental Microbiology, 2006Co-Authors: Elizabeth K Costello, Steven K SchmidtAbstract:Cold, water-saturated soils play important biogeochemical roles, yet almost nothing is known about the identity and habitat of microbes active under such conditions. We investigated the year-round microenvironment of an Alpine Tundra wet meadow soil in the Colorado Rocky Mountains, focusing on the biogeochemistry and microbial diversity of spring snowmelt--a dynamic time for Alpine ecosystems. In situ measurements revealed spring and autumn periods of long-term temperature stability near 0 degrees C, and that deeper soil (30 cm) was more stable than surface soil, with more moderate summers and winters, and longer isothermal phases. The soil was saturated and water availability was limited by freezing rather than drying. Analyses of bioavailable redox species showed a shift from Mn reduction to net Fe reduction at 2-3 cm depth, elevated SO4(2-) and decreased soluble Zn at spring snowmelt. Terminal restriction fragment length polymorphism profiles detected a correlated shift in bacterial community composition at the surface to subsurface transition. Bacterial and archaeal small-subunit rRNA genes were amplified from saturated spring soil DNA pooled along a depth profile. The most remarkable feature of these subsurface-biased libraries was the high relative abundance of novel, uncultivated Chloroflexi-related sequences comprising the third largest bacterial division sampled, and representing seven new Chloroflexi subdivisions, thereby dramatically expanding the known diversity of this bacterial division. We suggest that these novel Chloroflexi are active at near -0 degrees C temperatures, under likely anoxic conditions, and utilize geochemical inputs such as sulfide from upslope weathering.
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endogenous methanogenesis stimulates oxidation of atmospheric ch4 in Alpine Tundra soil
Microbial Ecology, 2002Co-Authors: Amy E West, Steven K SchmidtAbstract:Experiments were done to test the hypothesis that atmospheric CH 4 oxidizers in a well-drained Alpine Tundra soil are supported by CH 4 production from anaerobic microsites in the soil. Soil was subjected to 22 days of anaerobic conditions with elevated H 2 and CO 2 in order to stimulate methanogenesis. This treatment stimulated subsequent atmospheric CH 4 consumption, probably by increasing soil methanogenesis. After removal from anaerobic conditions, soils emitted CH 4 for up to 6 h, then oxidized atmospheric CH 4 at 111 (±5.7) pmol (g dry weight) -1 h -1 , which was more than 3 times the rate of control soils. Further supporting our hypothesis, additions of lumazine, a highly specific inhibitor of methanogenesis, prevented the stimulation of atmospheric CH 4 oxidation by the anaerobic treatment. The method used to create anaerobic conditions with elevated H 2 and CO 2 also elevated headspace CH 4 concentrations. However, elevated CH 4 concentrations under aerobic conditions did not stimulate CH 4 oxidation as much as preexposure to H 2 and CO 2 under anaerobic conditions. Anaerobic conditions created by N 2 flushing did not stimulate atmospheric CH 4 oxidation, probably because N 2 flushing inhibited methanogenesis by removing necessary precursors for methane production. We conclude that anaerobic conditions with elevated H 2 and CO 2 stimulate atmospheric CH 4 oxidation in this dry Alpine Tundra soil by increasing endogenous CH 4 production. This effect was prevented by inhibiting methanogenesis, indicating the importance of endogenous CH 4 production in a CH 4 -consuming soil.
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acetate stimulates atmospheric ch4 oxidation by an Alpine Tundra soil
Soil Biology & Biochemistry, 1999Co-Authors: Amy E West, Steven K SchmidtAbstract:Abstract Experiments were conducted to determine the effects of various carbon substrates on the oxidation of atmospheric CH 4 by an Alpine Tundra soil. Acetate, formate, methanol, trimethylamine and yeast extract were tested. Acetate and formate (500 μg C (g d.w.) −1 ) stimulated CH 4 oxidation rates from 300 to 1192.8 (±97.2) and 1036.8 (±33.6) pg C (g d.w.) −1 h −1 , respectively. In contrast, methanol did not cause an increase in maximal CH 4 oxidation rates, but methanol-treated soil maintained peak rates of CH 4 oxidation longer than control soil. In parallel with the CH 4 data, acetate additions stimulated acetate utilization, whereas methanol did not stimulate methanol utilization in the soil. This indicates that the mechanism by which acetate stimulates soil CH 4 oxidation may not be the same as that by which methanol sustains soil CH 4 oxidation. Growth of methanotrophs on acetate has not been reported previously. Therefore, these data indicate that either there is a novel strain of methanotroph in this soil, or that acetate stimulates atmospheric CH 4 oxidation by increasing methanogenesis, which in turn increases the supply of methane to the methane oxidizers in this soil.
John F. Knowles - One of the best experts on this subject based on the ideXlab platform.
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evidence for non steady state carbon emissions from snow scoured Alpine Tundra
Nature Communications, 2019Co-Authors: John F. Knowles, Peter D. Blanken, Corey R. Lawrence, Mark W. WilliamsAbstract:High-latitude warming is capable of accelerating permafrost degradation and the decomposition of previously frozen carbon. The existence of an analogous high-altitude feedback, however, has yet to be directly evaluated. We address this knowledge gap by coupling a radiocarbon-based model to 7 years (2008–2014) of continuous eddy covariance data from a snow-scoured Alpine Tundra meadow in Colorado, USA, where solifluction lobes are associated with discontinuous permafrost. On average, the ecosystem was a net annual source of 232 ± 54 g C m−2 (mean ± 1 standard deviation) to the atmosphere, and respiration of relatively radiocarbon-depleted (i.e., older) substrate contributes to carbon emissions during the winter. Given that Alpine soils with permafrost occupy 3.6 × 106 km2 land area and are estimated to contain 66.3 Pg of soil organic carbon (4.5% of the global pool), this scenario has global implications for the mountain carbon balance and corresponding resource allocation to lower elevations. The potential contribution of high altitude permafrost as a climate feedback is unknown. Here the authors show seven years of sustained carbon emissions from snow-scoured Alpine Tundra including respiration of older carbon substrate from solifluction lobes associated with permafrost during the winter.
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Evidence for non-steady-state carbon emissions from snow-scoured Alpine Tundra
Nature Publishing Group, 2019Co-Authors: John F. Knowles, Peter D. Blanken, Corey R. Lawrence, Mark W. WilliamsAbstract:The potential contribution of high altitude permafrost as a climate feedback is unknown. Here the authors show seven years of sustained carbon emissions from snow-scoured Alpine Tundra including respiration of older carbon substrate from solifluction lobes associated with permafrost during the winter
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energy and surface moisture seasonally limit evaporation and sublimation from snow free Alpine Tundra
Agricultural and Forest Meteorology, 2012Co-Authors: John F. Knowles, Peter D. Blanken, Mark W. Williams, Kurt ChowanskiAbstract:This study highlights the importance of landscape position and resultant snow accumulation to the hydrologic balance of snow-free Alpine Tundra, and suggests that modeling studies must account for seasonally dissimilar partitioning of the energy balance in order to accurately predict evaporation and/or sublimation. The eddy covariance method was used to measure the surface energy balance above high-elevation (3502 m above sea level) Alpine Tundra at Niwot Ridge, CO, over 3 years from 2007 to 2009. During the winter the site was characterized by wind scour, with little snow accumulation. Two co-located towers afforded the opportunity to constrain the influence of complex mountain topography on measurement uncertainty, and overall errors were comparable to other FLUXNET sites. Random measurement uncertainty for the turbulent fluxes was approximately 10% of midday summertime values. The 0.5-h mean energy balance closure was 81% over the entire measurement period, and improved to 91% during the summer when the magnitude of the turbulent fluxes was larger. In spite of 955 mm mean annual precipitation, the 24-h mean evaporative fraction was 0.39, typical of dry grassland or rangeland ecosystems. These low values were attributed to rapid, efficient removal of snow by prevailing windy conditions throughout the winter. During the summer when rainfall provided moisture, evaporation was principally limited by available energy. Overall, an average of 39% of annual precipitation was evaporated or sublimated back to the atmosphere. We conclude that the annual distribution of precipitation is an essential control on evaporation and sublimation from this ecosystem.
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a comparison of water and carbon dioxide exchange at a windy Alpine Tundra and subAlpine forest site near niwot ridge colorado
Biogeochemistry, 2009Co-Authors: Peter D. Blanken, Sean P Burns, Russell K. Monson, John F. Knowles, Mark W. Williams, Kurt Chowanski, Todd AckermanAbstract:Eddy covariance measurements of the surface energy balance and carbon dioxide exchange above high-elevation (3,480 m above sea level) Alpine Tundra located near Niwot Ridge, Colorado, were compared to simultaneous measurements made over an adjacent subAlpine forest over two summers and one winter, from June 9, 2007 to July 3, 2008. The surface energy balance closure at the Alpine site averaged 71 and 91%, winter and summer, respectively, due to the high wind speeds, short turbulent flux footprint, and relatively flat ridge-top location of the measurement site. Throughout the year, the Alpine site was cooler with higher relative humidity, and had a higher horizontal wind speed, especially in winter, compared to the forest site. Wind direction was persistently downslope at the Alpine site (summer and winter, day and night), whereas upslope winds were common at the forest site during summer daytime periods. The latent and sensible heat fluxes were consistently larger in magnitude at the forest site, with the largest differences during summer. The horizontal advective flux of CO2 at the Alpine site averaged 6% of the net ecosystem exchange (NEE) during summer nights (5% during summer daytime), and was small in relation to the high wind speeds, relatively flat site, and weak sources of CO2 upwind of the site. The magnitudes and diurnal behavior of the Alpine NEE calculated using three methods; eddy-covariance, friction velocity filter, and with advection and storage calculations, gave similar results. The period of net CO2 uptake (negative NEE) was 100 days at the Alpine site with a net uptake of 16 g C m−2, compared to 208 days at the forest site with a net uptake of 108 g C m−2, with initiation of net uptake coinciding with air temperatures reaching +10°C. Winter respiration loss at the Alpine site was 164 g C m−2 over 271 days, compared to 52 g C m−2 over 175 days at the forest site, with the initiation of net loss coinciding with air temperatures reaching −10°C at each site.
Jing Wei - One of the best experts on this subject based on the ideXlab platform.
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distribution patterns of vegetation biomass and nutrients bio cycle in Alpine Tundra ecosystem on changbai mountains northeast china
Journal of Forestry Research, 2007Co-Authors: Jing Wei, Ping JiangAbstract:A study was conducted to test the correlation between biomass and elevation and the differences in concentration and storks of nutrients among five vegetation types (Felsenmeer Alpine Tundra vegetation-FA, Lithic Alpine Tundra vegetation-LA, Typical Alpine Tundra vegetation-TA, Meadow Alpine Tundra vegetation-MA, and Swamp Alpine Tundra vegetation-SA) on Alpine Tundra of Changbai Mountains, Jilin Province, China in growing seasons of 2003, 2004 and 2005. The biomass of 43 mono-species and soil nutrients in Alpine Tundra ecosystem were also investigated. Dominant species from Ericaceae (such as Rhododendron chrysanthum and Vaccinium jliginosum var. alpinum) were taken to analyze organ biomass distribution. Result showed that the biomass and elevation had a significant correlation (Biomass=−237.3 ln(Elevation) +494.36; R2=0.8092; P<0.05). No significant differences were found in phosphorus and sulphur concentrations of roots, stems and leaves among the five vegetation types. There were significant differences in nitrogen and phosphorus stocks of roots, stems and leaves and in sulphur stock of stems and leaves among TA, MA, and SA vegetation types (p<0.05). The nutrient stock of five vegetations was averagely 72.46 kg·hm−2, of which N, P, S were 48.55, 10.33 and 13.61 kg·hm−2, respectively. Soil N and S concentrations in meadow Alpine Tundra soil type was significantly higher than those in other four soil types (Cold desert Alpine Tundra soil, Lithic Alpine Tundra soil, Peat Alpine Tundra soil, and Gray Alpine Tundra soil). Phosphorous concentration in SA type was higher (p<0.05) than in other types. Soil nutrient stock (0–20cm) was averagely 39.59 t·hm−2, of which N, P, S were 23.74, 5.86, 9.99 t·hm−2, respectively.
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nutrients and biomass spatial patterns in Alpine Tundra ecosystem on changbai mountains northeast china
Colloids and Surfaces B: Biointerfaces, 2007Co-Authors: Ping Jiang, Jing Wei, Hongbo ShaoAbstract:Biomass and nutrients were investigated in 2003, 2004 and 2005 growing seasons by using a chronosequence of five vegetation types in Alpine Tundra on Changbai Mountains. The objective of this study was to test whether nutrients at biointerfaces were significant differences among five vegetation types. The biomass and elevation are highly related (biomass=-237.3ln(elevation)+494.36; R(2)=0.8092; p<0.05). There were no significant differences in phosphorus (P) and sulphur (S) concentrations of roots, stems and leaves among five vegetation types while there are significant differences in nitrogen (N) and P stocks of roots, stems and leaves and in S stock of stems and leaves among typical Alpine Tundra vegetation (TA), meadow Alpine Tundra vegetation (MA), and swamp Alpine Tundra vegetation (SA) (p<0.05). Vegetation nutrients stock is averagely 72.46kg hm(-2), and N, P, S stocks are 48.55, 10.33 and 13.61kg hm(-2), respectively. Soil N and S concentrations in MA are significantly higher than those in other four soil types. P is higher in SA (p<0.05). Soil nutrients stock (0-20cm) is averagely 39.59t hm(-2), and N, P, S stocks are 23.74, 5.86 and 9.99t hm(-2), respectively.
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carbon storage and flux for Alpine Tundra ecosystems in changbai mountains northeast china
Journal of Forestry Research, 2007Co-Authors: Yongxiang Wang, Jing Wei, Ping Jiang, Hongchang WangAbstract:This paper examined the carbon storage and flux of vegetation-litter-soil in Alpine Tundra ecosystems in Changbai Mountains, Approximately 17251 t∙a^(-1) of carbon was yearly stored in the vegetation and 15043.1 t∙a^(-1) of carbon flew into soil by litters. The vegetation-litter-soil ecosystem stored 452624 t∙a^(-1) of carbon, which was the important CO2 sink. The net carbon storage was currently 3146 t∙a^(-1) vegetation-litter-soil ecosystem.
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nutrient cycling in an Alpine Tundra ecosystem on changbai mountain northeast china
Applied Soil Ecology, 2006Co-Authors: Jing Wei, Hong-bing Deng, Jingzhu ZhaoAbstract:Nutrient availability regulates the responses of high-latitude ecosystems to climate change but nitrogen, phosphorus and sulfur biogeochemistry, especially, phosphorus and sulfur cycles, are poorly understood in Alpine Tundra ecosystem. This study examines the cycling of nutrients in a 302-year-old Alpine Tundra ecosystem in which litter has accumulated through compartment methods. Samples of the vegetation, litter and soil components were collected and chemically analyzed for nitrogen (N), phosphorus (P) and sulfur (S). Overall, nutrient budgets for N, P and S pool sizes were determined. Although there were large reserves of N (24,640 kg hm(-2)), P (5860 kg hm(-2)) and S (10,018.7 kg hm(-2)) in soil layers (0-20 cm), the nutrient reserves within the litter and fine roots within surface soil layer (0-10 cm) were well balanced, indicating that a tightly closed plant-litter-soil-plant nutrient cycle was in operation for the cycling of N, P and S. The litter helped the retention of as many nutrients as possible in Alpine Tundra system. (c) 2005 Elsevier B.V. All rights reserved.
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phosphorus and sulphur bio cycling in Alpine Tundra ecosystem of changbai mountains
Journal of Applied Ecology, 2005Co-Authors: Jing Wei, Ying-jie Hao, Huan Wang, Wen-yan ShangAbstract:The study with compartment model on the phosphorus (P) and sulphur (S) bio-cycling in Alpine Tundra ecosystem of Changbai Mountains showed that the total storage of P and S was 16 088.6 t and 26 079.4 t, of which, 46.14 t and 64.82 t was in vegetation pool, 89.63 t and 53.16 t in litterfall pool, and 15952.8 t and 26014.6 t in soil pool, respectively. The above- and below-ground vegetation pool stored 21.88 t and 44.21 t, and 24.28 t and 20.61 t of P and S, respectively, and the above-ground vegetation pool had 47.4% of P and 68.2% of S in the vegetation subsystem. The transferable P amount was 24.25 t x yr(-1) through plant absorption and 31.59 t x yr(-1) through litterfall return, while the transferable S amount was 31.18 t x yr(-1), 10.12 t x yr(-1) and 21.06 t x yr(-1) in the aboveground plant, belowground root system, and litterfall return, respectively. The natural return ratio of S was 67.5%.
Peter D. Blanken - One of the best experts on this subject based on the ideXlab platform.
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evidence for non steady state carbon emissions from snow scoured Alpine Tundra
Nature Communications, 2019Co-Authors: John F. Knowles, Peter D. Blanken, Corey R. Lawrence, Mark W. WilliamsAbstract:High-latitude warming is capable of accelerating permafrost degradation and the decomposition of previously frozen carbon. The existence of an analogous high-altitude feedback, however, has yet to be directly evaluated. We address this knowledge gap by coupling a radiocarbon-based model to 7 years (2008–2014) of continuous eddy covariance data from a snow-scoured Alpine Tundra meadow in Colorado, USA, where solifluction lobes are associated with discontinuous permafrost. On average, the ecosystem was a net annual source of 232 ± 54 g C m−2 (mean ± 1 standard deviation) to the atmosphere, and respiration of relatively radiocarbon-depleted (i.e., older) substrate contributes to carbon emissions during the winter. Given that Alpine soils with permafrost occupy 3.6 × 106 km2 land area and are estimated to contain 66.3 Pg of soil organic carbon (4.5% of the global pool), this scenario has global implications for the mountain carbon balance and corresponding resource allocation to lower elevations. The potential contribution of high altitude permafrost as a climate feedback is unknown. Here the authors show seven years of sustained carbon emissions from snow-scoured Alpine Tundra including respiration of older carbon substrate from solifluction lobes associated with permafrost during the winter.
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Evidence for non-steady-state carbon emissions from snow-scoured Alpine Tundra
Nature Publishing Group, 2019Co-Authors: John F. Knowles, Peter D. Blanken, Corey R. Lawrence, Mark W. WilliamsAbstract:The potential contribution of high altitude permafrost as a climate feedback is unknown. Here the authors show seven years of sustained carbon emissions from snow-scoured Alpine Tundra including respiration of older carbon substrate from solifluction lobes associated with permafrost during the winter
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energy and surface moisture seasonally limit evaporation and sublimation from snow free Alpine Tundra
Agricultural and Forest Meteorology, 2012Co-Authors: John F. Knowles, Peter D. Blanken, Mark W. Williams, Kurt ChowanskiAbstract:This study highlights the importance of landscape position and resultant snow accumulation to the hydrologic balance of snow-free Alpine Tundra, and suggests that modeling studies must account for seasonally dissimilar partitioning of the energy balance in order to accurately predict evaporation and/or sublimation. The eddy covariance method was used to measure the surface energy balance above high-elevation (3502 m above sea level) Alpine Tundra at Niwot Ridge, CO, over 3 years from 2007 to 2009. During the winter the site was characterized by wind scour, with little snow accumulation. Two co-located towers afforded the opportunity to constrain the influence of complex mountain topography on measurement uncertainty, and overall errors were comparable to other FLUXNET sites. Random measurement uncertainty for the turbulent fluxes was approximately 10% of midday summertime values. The 0.5-h mean energy balance closure was 81% over the entire measurement period, and improved to 91% during the summer when the magnitude of the turbulent fluxes was larger. In spite of 955 mm mean annual precipitation, the 24-h mean evaporative fraction was 0.39, typical of dry grassland or rangeland ecosystems. These low values were attributed to rapid, efficient removal of snow by prevailing windy conditions throughout the winter. During the summer when rainfall provided moisture, evaporation was principally limited by available energy. Overall, an average of 39% of annual precipitation was evaporated or sublimated back to the atmosphere. We conclude that the annual distribution of precipitation is an essential control on evaporation and sublimation from this ecosystem.
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a comparison of water and carbon dioxide exchange at a windy Alpine Tundra and subAlpine forest site near niwot ridge colorado
Biogeochemistry, 2009Co-Authors: Peter D. Blanken, Sean P Burns, Russell K. Monson, John F. Knowles, Mark W. Williams, Kurt Chowanski, Todd AckermanAbstract:Eddy covariance measurements of the surface energy balance and carbon dioxide exchange above high-elevation (3,480 m above sea level) Alpine Tundra located near Niwot Ridge, Colorado, were compared to simultaneous measurements made over an adjacent subAlpine forest over two summers and one winter, from June 9, 2007 to July 3, 2008. The surface energy balance closure at the Alpine site averaged 71 and 91%, winter and summer, respectively, due to the high wind speeds, short turbulent flux footprint, and relatively flat ridge-top location of the measurement site. Throughout the year, the Alpine site was cooler with higher relative humidity, and had a higher horizontal wind speed, especially in winter, compared to the forest site. Wind direction was persistently downslope at the Alpine site (summer and winter, day and night), whereas upslope winds were common at the forest site during summer daytime periods. The latent and sensible heat fluxes were consistently larger in magnitude at the forest site, with the largest differences during summer. The horizontal advective flux of CO2 at the Alpine site averaged 6% of the net ecosystem exchange (NEE) during summer nights (5% during summer daytime), and was small in relation to the high wind speeds, relatively flat site, and weak sources of CO2 upwind of the site. The magnitudes and diurnal behavior of the Alpine NEE calculated using three methods; eddy-covariance, friction velocity filter, and with advection and storage calculations, gave similar results. The period of net CO2 uptake (negative NEE) was 100 days at the Alpine site with a net uptake of 16 g C m−2, compared to 208 days at the forest site with a net uptake of 108 g C m−2, with initiation of net uptake coinciding with air temperatures reaching +10°C. Winter respiration loss at the Alpine site was 164 g C m−2 over 271 days, compared to 52 g C m−2 over 175 days at the forest site, with the initiation of net loss coinciding with air temperatures reaching −10°C at each site.