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  • Wiley  (9)
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  • 1
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    Spatial scale effect on seasonal streamflows in permafrost catchments on the Qinghai-Tibet Plateau (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: The scale issue is of central concern in hydrological processes to understand the potential upscaling or downscaling methodologies, and to develop models for scaling the dominant processes at different scales and in different environments. In this study, a typical permafrost watershed in the Qinghai-Tibet Plateau was selected. Its hydrological processes were monitored for four years from 2004 to 2008; measuring the effects of freezing and thawing depth of active soil layers on runoff processes. To identify the nature and cause of variation in the runoff response in different size catchments, catchments ranging from 1.07 km 2 to 112 km 2 were identified in the watershed. The results indicated that the variation of runoff coefficients showed a “V” shape with increasing catchment size during the spring and autumn seasons, when the active soil was subjected to thawing or freezing processes. A two-stage method was proposed to create runoff scaling models to indicate the effects of scale on runoff processes. In summer, the scaling transition model followed an exponential function for mean daily discharge, whereas the scaling model for flood flow exhibited a linear function. In autumn, the runoff process transition across multiple scales followed an exponential function with air temperature as the driving factor. These scaling models demonstrate relatively high simulation efficiency and precision, and provide a practical way for upscaling or downscaling runoff processes in a medium-size permafrost watershed. For permafrost catchments of this scale, the results show that the synergistic effect of scale and vegetation cover is an important driving factor in the runoff response. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 2
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    Development of a three-dimensional watershed modelling system for water cycle in the middle part of the Heihe rivershed, in the west of China (2011)
    Wiley
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    Publication Date: 2011-01-25
    Description: A three-dimensional numerical modelling system is developed to study transformation processes of water resources in alluvial fan and river basin along the middle reaches of the Heihe River Basin, Northwest China, an arid and semi-arid region. Integrating land utilization, remote sensing and geographic information systems, we have developed a numerical modelling system that can be used to quantify the effects of land use and anthropogenic activities on the groundwater system as well as to investigate the interaction between surface water and groundwater. Various hydraulic measurements are used to identify and calibrate the hydraulic boundary conditions and spatial distributions of hydraulic parameters. In the modelling study, various water exchanges and human effects on the watershed system are considered. These include water exchange between surface water and groundwater, groundwater pumping, lateral water recharges from mountain areas, land utilization, and infiltration and evaporation in the irrigation and non-irrigation areas. The modelling system provides a quantitative method to describe spatial and temporal distributions and transformations between various water resources, and it has application to other watersheds in arid and semi-arid areas. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 3
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    Simulation of soil thermal dynamics using an artificial neural network model for a permafrost alpine meadow on the Qinghai–Tibetan plateau (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract The thermal regime of the active layer temperature (ALT) is a key variable with which to monitor permafrost changes and to improve the precision of simulations and predictions of land surface processes. The dynamics of the active layer thermal regime can differ substantially under various land surface types and climatic conditions. The proper simulation of these different processes is essential for accurately predicting the changes in water cycles and ecosystems under a warming climate scenario. In this paper, an artificial neural network (ANN) forecasting model system was developed using only two accessible parameters, air and ground surface temperatures, to predict and simulate the ALT thermal regime. The model results show that the ANN model has better real‐time prediction capability than other physics‐based models and performs well at simulating and forecasting variations in soil temperature with a step size of 12 days in permafrost regions on the Qinghai–Tibetan Plateau. The influence of an increase in air temperature on the ALT thermal regime was more intense during the thawing process than during the freezing process, and this influence decreased with an increase in soil depth.
    Print ISSN: 1045-6740
    Electronic ISSN: 1099-1530
    Topics: Geography , Geosciences
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  • 4
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    A Carbon Flux Assessment Driven by Environmental Factors Over the Tibetan Plateau and Various Permafrost Regions (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract In this study, the spatiotemporal changes in net primary production (NPP) and drivers, including climate change, atmospheric CO2 concentration and land use change, over the Tibetan Plateau from 1979 to 2016 were investigated using the version 4.5 of the Community Land Model. Based on high‐resolution atmospheric forcing data, six numerical experiments were designed to assess the relative contribution of different environmental factors on NPP. Our simulation results suggest that NPP over the Tibetan Plateau has increased significantly at a rate of 2.25 Tg C/year2 since 1979. At the plateau scale, changes in precipitation, CO2 concentration, and land use change contributed approximately 63.3%, 16.7%, and 9.5% to the interannual variation of NPP, respectively. Temperature did not exert a significant effect on the trends of NPP, which results from the increasing temperature enhancing the autotrophic respiration (AR) more than the gross primary production. We also divided the alpine grasslands into four types, including alpine meadow of permafrost, alpine steppe of permafrost, alpine meadow of seasonal frost, and alpine steppe of seasonal frost. We found that the increasing rate of NPP in permafrost regions was significantly higher than that in seasonal frost regions. Compared with other factors, precipitation change played a dominant role in the NPP over the four different types of grasslands. Temperature‐induced change on NPP and AR was larger in the alpine meadow regions compared to in the alpine steppe regions. In addition, NPP and AR showed a more remarkable response to temperature change over alpine meadow of permafrost than other regions.
    Print ISSN: 2169-8953
    Electronic ISSN: 2169-8961
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Anthropogenic nitrogen deposition increases soil carbon by enhancing new carbon of the soil aggregate formation (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Anthropogenic nitrogen (N) deposition can most likely increase temperate forest soil organic carbon (SOC) storage. Increased SOC is usually suggested to be associated with the suppression of SOC decomposition, which has been hypothesized to be due to the decrease in the activity of lignin‐degrading extracellular enzymes and/or the decrease in soil acidity under N‐addition. However, the potential mechanism of SOC protection derived from N‐addition is less understood. Here, in a low‐deposition temperate montane forest, short‐term N‐addition could increase SOC storage in the aggregate fraction but not in the bulk soil. N‐induced SOC accumulation was partly associated with the suppressed SOC decomposition (indicated by lower soil respiration) that resulted from the reduced microbial biomass rather than from decreased lignin‐degrading enzyme activity or from reduced soil acidity. In addition, N‐addition promoted soil aggregate formation, which could partly suppress SOC decomposition by protecting new carbon that originated from plant litter residue to a greater degree, while dissolved organic carbon retention in the mineral soils played a limited role in the SOC sequestration derived from N‐addition, at least in the short term. A conceptual model was proposed and highlighted a new underlying mechanism of new carbon protection by enhanced aggregate formation, other than the role of microbial suppression, to explain the positive effect of anthropogenic N deposition on forest SOC.
    Print ISSN: 2169-8953
    Electronic ISSN: 2169-8961
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Stable isotope variations of precipitation and streamflow reveal the young water fraction of a permafrost watershed (2016)
    Wiley
    Details
    Publication Date: 2016-11-12
    Description: The streamflow age is an essential descriptor of catchment functioning that controls runoff generation, biogeochemical cycling, and contaminant transport. The young water fraction (F yw ) of streamflow, which can be accurately estimated with tracer data, is effective at characterizing the water age proportions of heterogeneous catchments. However, the F yw values of permafrost catchments are not known. We selected a watershed in the permafrost region of the Qinghai-Tibet Plateau (QTP) as our study area. Daily interval stable isotopes (deuterium and oxygen-18) of precipitation and streamflow were studied during the 2009 thawing season. The results show that the stable isotope compositions of precipitation and stream water have significant spatial and temporal variations. HYSPLIT backwards trajectory results demonstrate that the moisture in the study area mainly derived from the westerlies and southern monsoons. Thawing processes in the active layer of the permafrost significantly altered the stable isotope compositions of the stream water. The soil temperature, soil moisture, and air temperature are the main drivers of the stable isotope variations in the stream water. We estimated the young water fractions of the five catchments in the study area, which was the first estimates of the F yw in permafrost catchments in the QTP. The results show that an average of 15% of the streamflow is younger than 43 days. Additional analyses show that the vegetation cover significantly controls the young water fraction of the streamflow. These results will improve our understanding of permafrost hydrological processes and water resource utilization and protection.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 7
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    Spatiotemporal variability and sources of DIC in permafrost catchments of the Yangtze River source region: insights from stable carbon isotope and water chemistry (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Riverine dissolved inorganic carbon (DIC) exports play a central role in the regional and global carbon cycles. Here, we investigated the spatiotemporal variability and sources of DIC in 8 catchments in the Yangtze River source region (YRSR) with variable permafrost coverage and seasonally thawed active layers. The YRSR catchments are DIC‐rich (averagely 25 mg C L‐1) and export 3.51 g m‐2 yr‐1 of DIC. The seasonal changes of temperature, active layer, flow path, and discharge can alter DIC and stable carbon isotope of DIC (δ13C‐DIC). The most depleted δ13C‐DIC values were found in the thawed period, suggesting the soil respired CO2 during the active layer thaw period can promote bicarbonate production via H2CO3 weathering. Spatially, δ13C‐DIC values increased downstream, likely due to CO2 outgassing and changed permafrost coverage and runoff. We found that evaporite dissolution and silicate weathering in the seasonally thawed active layer contributed 44.2% and 30.9% of stream HCO3‐, respectively; while groundwater and rainwater contributed 16.7% and 7.3% of HCO3‐, respectively. Pure carbonate rock weathering played a negligible role in DIC production. These results were compatible with δ13C‐DIC source approximation results. Silicate weathering increased from initial thaw to thawed period, reflecting the active layer thaw and subsequent hydrology change impacts. Silicate weathering consumed 1.25×1010 mol of CO2 annually, while evaporite dissolution may produce CO2 and neutralize this CO2 sink. This study provides new understanding of the riverine DIC export processes of the YRSR. As permafrost degrades, the quantity, sources, and sinks of riverine DIC may also change spatiotemporally.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Impact of land use changes on soil carbon, nitrogen and phosphorus and water pollution in an arid region of northwest China (2006)
    Wiley
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    Publication Date: 2006-01-18
    Print ISSN: 0266-0032
    Electronic ISSN: 1475-2743
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley on behalf of British Society of Soil Science.
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  • 9
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    Impact of land use changes on soil carbon, nitrogen and phosphorus and water pollution in an arid region of northwest China (2004)
    Wiley
    Details
    Publication Date: 2004-03-01
    Print ISSN: 0266-0032
    Electronic ISSN: 1475-2743
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley on behalf of British Society of Soil Science.
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