In Situ Measurements of Organic Carbon in Soil Profiles Using vis-NIR Spectroscopy on the Qinghai–Tibet Plateau

2015 ◽  
Vol 49 (8) ◽  
pp. 4980-4987 ◽  
Author(s):  
Shuo Li ◽  
Zhou Shi ◽  
Songchao Chen ◽  
Wenjun Ji ◽  
Lianqing Zhou ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Nir Spectroscopy ◽  
In Situ Measurements ◽  
Tibet Plateau ◽  
Soil Profiles ◽  
Qinghai Tibet Plateau

scholarly journals Brief Communication: Evaluation and comparisons of permafrost map over Qinghai-Tibet Plateau based on inventory of in-situ evidence

2018 ◽  
Author(s):  
Bin Cao ◽  
Tingjun Zhang ◽  
Qinghai Wu ◽  
Yu Sheng ◽  
Lin Zhao ◽  
...  
Keyword(s):  
Controlling Factors ◽  
In Situ Measurements ◽  
Tibet Plateau ◽  
Permafrost Region ◽  
Improved Method ◽  
Limited Evidence ◽  
Wide Range ◽  
Communication Evaluation ◽  
Qinghai Tibet Plateau

Abstract. Many maps have been produced to estimate permafrost distribution over the Qinghai-Tibet Plateau, however, the evaluation and comparisons of them are poorly understood due to limited evidence. Using a large number data from various sources, we present the inventory of permafrost presence/absence with 1475 sites/plots over the QTP. Based on the in-situ measurements, our evaluation results showed a wide range of map performance with the overall accuracy of about 59–82 %, and the estimated permafrost region (1.42–1.84 × 106 km2) and area (0.76–1.25 × 106 km2) are extremely large. The low agreement in areas near permafrost boundary and fragile landscapes require improved method considering more controlling factors at both medium-large and local scales.

scholarly journals Brief communication: Evaluation and inter-comparisons of Qinghai–Tibet Plateau permafrost maps based on a new inventory of field evidence

2019 ◽  
Vol 13 (2) ◽  
pp. 511-519 ◽  
Author(s):  
Bin Cao ◽  
Tingjun Zhang ◽  
Qingbai Wu ◽  
Yu Sheng ◽  
Lin Zhao ◽  
...  
Keyword(s):  
Kappa Coefficient ◽  
Controlling Factors ◽  
In Situ Measurements ◽  
Tibet Plateau ◽  
Field Evidence ◽  
Wide Range ◽  
Communication Evaluation ◽  
Qinghai Tibet Plateau ◽  
Variable Landscapes

Abstract. Many maps have been produced to estimate permafrost distribution over the Qinghai–Tibet Plateau (QTP), but the errors and biases among them are poorly understood due to limited field evidence. Here we evaluate and inter-compare the results of six different QTP permafrost maps with a new inventory of permafrost presence or absence comprising 1475 field sites compiled from various sources. Based on the in situ measurements, our evaluation results showed a wide range of map performance, with Cohen's kappa coefficient from 0.21 to 0.58 and an overall accuracy between about 55 % and 83 %. The low agreement in areas near the boundary between permafrost and non-permafrost and in spatially highly variable landscapes highlights the need for improved mapping methods that consider more controlling factors at both medium–large and local scales.

The Carbon:²³⁴Thorium ratios of sinking particles in the California Current Ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model

2019 ◽  
Author(s):  
Michael Stukel ◽  
Thomas Kelly
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Transport Model ◽  
California Current ◽  
In Situ Measurements ◽  
Power Law Distribution ◽  
Sinking Particles ◽  
Organic Carbon Concentration

Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon:thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U-234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.

scholarly journals Reduced microbial stability in the active layer is associated with carbon loss under alpine permafrost degradation

2021 ◽  
Vol 118 (25) ◽  
pp. e2025321118
Author(s):  
Ming-Hui Wu ◽  
Sheng-Yun Chen ◽  
Jian-Wei Chen ◽  
Kai Xue ◽  
Shi-Long Chen ◽  
...  
Keyword(s):  
Active Layer ◽  
Tibet Plateau ◽  
Permafrost Degradation ◽  
Soil C ◽  
C Cycling ◽  
Microbial Stability ◽  
The Stability ◽  
Qinghai Tibet Plateau ◽  
Permafrost Regions

Permafrost degradation may induce soil carbon (C) loss, critical for global C cycling, and be mediated by microbes. Despite larger C stored within the active layer of permafrost regions, which are more affected by warming, and the critical roles of Qinghai-Tibet Plateau in C cycling, most previous studies focused on the permafrost layer and in high-latitude areas. We demonstrate in situ that permafrost degradation alters the diversity and potentially decreases the stability of active layer microbial communities. These changes are associated with soil C loss and potentially a positive C feedback. This study provides insights into microbial-mediated mechanisms responsible for C loss within the active layer in degraded permafrost, aiding in the modeling of C emission under future scenarios.

scholarly journals Estimation of Soil Organic Carbon Storage in Palustrine Wetlands, China

2020 ◽  
Vol 17 (13) ◽  
pp. 4646
Author(s):  
Lu Han ◽  
Zhongmei Wan ◽  
Yuedong Guo ◽  
Changchun Song ◽  
Shaofei Jin ◽  
...  
Keyword(s):  
Data Collection ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Measurement Data ◽  
Carbon Stocks ◽  
Tibet Plateau ◽  
Accurate Estimation ◽  
Organic Carbon Content ◽  
Actual Measurement ◽  
Qinghai Tibet Plateau

Wetlands regulate the balance of global organic carbon. Small changes in the carbon stocks of wetland ecosystem play a crucial role in the regional soil carbon cycle. However, an accurate estimation of carbon stocks is still be debated for China’s wetlands ecosystem due to the limitation of data collection and methodology. Here, we investigate the soil organic carbon (SOC) storage in a 1-m depth in China’s palustrine wetlands. A total of 1383 sample data were collected from palustrine wetlands in China. The data sources are divided into three parts, respectively, data collection from published literature, data from books, and actual measurement data of sample points. The results demonstrate that there is considerable SOC storage in China’s palustrine wetlands (9.945 Pg C), primarily abundant in the northeast, northwest arid and semi-arid as well as Qinghai-Tibet Plateau regions. The SOC density in per unit area soil was higher in the wetland area of northeast, southwest and Qinghai-Tibet plateau. Within China terrestrial scale, the temperature and precipitation differences caused by latitude were the main environmental factors affecting the organic carbon content. Furthermore, except for the southeast and south wetland region, SOC content decreased with depth.

scholarly journals Response of soil organic carbon to vegetation degradation along a moisture gradient in a wet meadow on the Qinghai-Tibet Plateau

2018 ◽  
Vol 8 (23) ◽  
pp. 11999-12010 ◽  
Author(s):  
Abdul-Rauf Malimanga Alhassan ◽  
Weiwei Ma ◽  
Guang Li ◽  
Zhirong Jiang ◽  
Jiangqi Wu ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Moisture Gradient ◽  
Tibet Plateau ◽  
Wet Meadow ◽  
Vegetation Degradation ◽  
Qinghai Tibet Plateau
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