Stable carbon isotopes as indicators for permafrost carbon vulnerability in upper reach of Heihe River basin, northwestern China

Mu, Cuicui; Zhang, Tingjun; Wu, Qingbai; Zhang, Tingjun; Cao, Bin; Wang, Qingfeng; Peng, Xiaoqing; Cheng, Guodong

doi:10.1016/j.quaint.2013.12.001

Cited by 35 publications

(20 citation statements)

References 33 publications

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“…According to the global database of soil types [ Eswaran et al ., ], the SOC and TN stocks in this area were comparable to the lowest values of Aridisols. In grasslands of the permafrost regions, where SOC were well preserved, the C:N ratios were usually higher than 17 [ Mu et al ., , ]. This could be explained if the production rate is higher than the decomposition rate, resulting in higher C:N ratios [ Post et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Environmental controls on soil organic carbon and nitrogen stocks in the high‐altitude arid western Qinghai‐Tibetan Plateau permafrost region

Zhao

Han

et al. 2016

JGR Biogeosciences

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While permafrost in the circum‐Artic has great influence on soil organic carbon (SOC) and total nitrogen (TN) stocks, this might not be the case in low‐latitude arid permafrost regions. We test this hypothesis in the western Qinghai‐Tibetan Plateau (QTP) permafrost region. Fifty‐nine soil profiles were analyzed to examine the SOC and TN distribution and the controlling factors in western QTP, which is a desert steppe ecoregion. Mean stocks of SOC (5.29 kg m−2) and TN (0.56 kg m−2) for the top 200 cm in this area were lower than those of the east QTP and circum‐Arctic regions. The SOC and TN stocks under vegetative cover with permafrost conditions were significantly higher than those of desert conditions. The SOC and TN stocks for the layers of different depths were related to the content of clay, silt, and moisture. Although the active layer thickness (ALT) had a significant negative correlation to soil moisture, the ALT explained little or no variance in the SOC and TN stocks. The results showed that in the vast permafrost regions of the western QTP, the SOC and TN stocks are very low, and the main controlling factors for the SOC and TN are soil texture, moisture, and vegetation type. The SOC pool in this area may not be as vulnerable to degradation associated with climate warming and thus not emit greenhouse gases at the same rate as other permafrost regions. The different response of the SOC in this region should be considered in carbon cycling models.

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Section: Discussionmentioning

confidence: 99%

Environmental controls on soil organic carbon and nitrogen stocks in the high‐altitude arid western Qinghai‐Tibetan Plateau permafrost region

Zhao

Han

et al. 2016

JGR Biogeosciences

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“…The region has an arid alpine climate with mean annual precipitation of 433 mm, mean annual potential evaporation of 1080 mm, and mean annual air temperature of −0.79°C, ranging from a monthly mean of 8.8°C in July to −11.8°C in February (data from 2012 to 2015). Soil organic carbon content ranges from 38.1 to 122.0 g kg −1 in the upper 50 cm [ Mu et al, ]. The permafrost temperature at a depth of 19 m is approximately −0.8°C, as measured from a borehole drilled in 2011.…”

Section: Methodsmentioning

confidence: 99%

Permafrost collapse shifts alpine tundra to a carbon source but reduces N₂O and CH₄ release on the northern Qinghai‐Tibetan Plateau

Abbott

Zhao

et al. 2017

Geophysical Research Letters

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Important unknowns remain about how abrupt permafrost collapse (thermokarst) affects carbon balance and greenhouse gas flux, limiting our ability to predict the magnitude and timing of the permafrost carbon feedback. We measured monthly, growing‐season fluxes of CO2, CH4, and N2O at a large thermokarst feature in alpine tundra on the northern Qinghai‐Tibetan Plateau (QTP). Thermokarst formation disrupted plant growth and soil hydrology, shifting the ecosystem from a growing‐season carbon sink to a weak source but decreasing feature level CH4 and N2O flux. Temperature‐corrected ecosystem respiration from decomposing permafrost soil was 2.7 to 9.5‐fold higher than in similar features from Arctic and Boreal regions, suggesting that warmer and dryer conditions on the northern QTP could accelerate carbon decomposition following permafrost collapse. N2O flux was similar to the highest values reported for Arctic ecosystems and was 60% higher from exposed mineral soil on the feature floor, confirming Arctic observations of coupled nitrification and denitrification in collapsed soils. Q10 values for respiration were typically over 4, suggesting high‐temperature sensitivity of thawed carbon. Taken together, these results suggest that QTP permafrost carbon in alpine tundra is highly vulnerable to mineralization following thaw, and that N2O production could be an important noncarbon permafrost climate feedback. Permafrost collapse altered soil hydrology, shifting the ecosystem from a carbon sink to carbon source but decreasing CH4 and N2O flux. Little to no vegetation recovery after stabilization suggests potentially large net carbon losses. High N2O flux compared to Arctic and Boreal systems suggests noncarbon permafrost climate feedback.

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“…Total water content was determined by drying the soil at 105 ∘ C for 8 hours and measuring the weight of the sample before and after drying. Every fifth sample was divided into half for quality assurance and quality control (Mu et al, 2014). The pH values of the soil suspensions (1:5 soil:water ratio) were measured with a pH meter.…”

Section: Soil Sampling and Analysismentioning

confidence: 99%

Sensitivity of soil organic matter decomposition to temperature at different depths in permafrost regions on the northern Qinghai‐Tibet Plateau

Zhang

Cao

et al. 2016

European J Soil Science

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The temperature sensitivity coefficient (Q10) of soil organic matter decomposition is an important variable for global climate models. Permafrost regions contain large organic carbon pools. A deep core was taken in permafrost from the northern Qinghai‐Tibet Plateau (QTP) and exposed to increases in temperature below and above 0°C. The production of CO2 was related to the soil organic carbon (SOC) contents and stable carbon isotopes. Smaller values of δ13C‐SOC and δ13C‐CO2 showed that the release of CO2 was primarily from soil with large SOC contents. The sensitivities of soil organic matter (SOM) decomposition to temperature near to the permafrost table and in some permafrost layers were larger than those in other layers. In some layers, a temperature increase below 0°C had a greater effect on the decomposition of SOM than one above 0°C. The values of Q10 in active layers varied from 2.7 to 23.0, with a mean of 8.8. The values of Q10 were larger in the deeper layers; they varied from 1.6 to 49.4, with a mean of 20.8. This is because the degradation of permafrost is usually associated with an increase in temperature even when the soil is in a frozen state. Our results suggest that the large values of Q10 at depth under frozen conditions merit more consideration of the response of SOC to climate warming in future research. Highlights The sensitivity to temperature coefficient, Q10, is an important property for global climate models. The values of Q10 for soil organic matter decomposition were also large in deep layers. A temperature increase below 0°C has large effects on Q10. The large values of Q10 at depth under frozen conditions merit more consideration.

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Stable carbon isotopes as indicators for permafrost carbon vulnerability in upper reach of Heihe River basin, northwestern China

Cited by 35 publications

References 33 publications

Environmental controls on soil organic carbon and nitrogen stocks in the high‐altitude arid western Qinghai‐Tibetan Plateau permafrost region

Environmental controls on soil organic carbon and nitrogen stocks in the high‐altitude arid western Qinghai‐Tibetan Plateau permafrost region

Permafrost collapse shifts alpine tundra to a carbon source but reduces N₂O and CH₄ release on the northern Qinghai‐Tibetan Plateau

Sensitivity of soil organic matter decomposition to temperature at different depths in permafrost regions on the northern Qinghai‐Tibet Plateau

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Stable carbon isotopes as indicators for permafrost carbon vulnerability in upper reach of Heihe River basin, northwestern China

Cited by 35 publications

References 33 publications

Environmental controls on soil organic carbon and nitrogen stocks in the high‐altitude arid western Qinghai‐Tibetan Plateau permafrost region

Environmental controls on soil organic carbon and nitrogen stocks in the high‐altitude arid western Qinghai‐Tibetan Plateau permafrost region

Permafrost collapse shifts alpine tundra to a carbon source but reduces N2O and CH4 release on the northern Qinghai‐Tibetan Plateau

Sensitivity of soil organic matter decomposition to temperature at different depths in permafrost regions on the northern Qinghai‐Tibet Plateau

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Permafrost collapse shifts alpine tundra to a carbon source but reduces N₂O and CH₄ release on the northern Qinghai‐Tibetan Plateau