title: A comparison of two methods for quantifying soil organic carbon of alpine grasslands on the Tibetan Plateau.
abstract: As CO2 concentrations continue to rise and drive global climate change, much effort has been put into estimating soil carbon (C) stocks and dynamics over time. However, the inconsistent methods employed by researchers hamper the comparability of such works, creating a pressing need to standardize the methods for soil organic C (SOC) quantification by the various methods. Here, we collected 712 soil samples from 36 sites of alpine grasslands on the Tibetan Plateau covering different soil depths and vegetation and soil types. We used an elemental analyzer for soil total C (STC) and an inorganic carbon analyzer for soil inorganic C (SIC), and then defined the difference between STC and SIC as SOCCNS. In addition, we employed the modified Walkley-Black (MWB) method, hereafter SOCMWB. Our results showed that there was a strong correlation between SOCCNS and SOCMWB across the data set, given the application of a correction factor of 1.103. Soil depth and soil type significantly influenced on the recovery, defined as the ratio of SOCMWB to SOCCNS, and the recovery was closely associated with soil carbonate content and pH value as well. The differences of recovery between alpine meadow and steppe were largely driven by soil pH. In addition, statistically, a relatively strong correlation between SOCCNS and STC was also found, suggesting that it is feasible to estimate SOCCNS stocks through the STC data across the Tibetan grasslands. Therefore, our results suggest that in order to accurately estimate the absolute SOC stocks and its change in the Tibetan alpine grasslands, adequate correction of the modified WB measurements is essential with correct consideration of the effects of soil types, vegetation, soil pH and soil depth.
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, Qinghai, People's Republic of China.
authors.forename: Litong
authors.initials: L
authors.lastname: Chen
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, Qinghai, People's Republic of China.
authors.forename: Dan F B
authors.initials: DF
authors.lastname: Flynn
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Jing
authors.affiliation: Department of Geosciences, Physical Geography and Soil Science, University of Tuebingen, Tuebingen, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Kühn
authors.affiliation: Department of Geosciences, Physical Geography and Soil Science, University of Tuebingen, Tuebingen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Scholten
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, Qinghai, People's Republic of China; Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, People's Republic of China.
authors.forename: Jin-Sheng
authors.initials: JS
authors.lastname: He
mesh_terms: D002119:Calcium Carbonate / Q000032:analysis* / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D057486:Carbon Cycle; D057231:Climate Change; D065948:Grassland; D012987:Soil / Q000737:chemistry*; D018609:Tibet
chemical_list: D012987:Soil; D002244:Carbon; D002119:Calcium Carbonate