Institute of Desertification Studies, Chinese Academy of Forestry, 100091 Beijing, China.
Institute of Desertification Studies, Chinese Academy of Forestry, 100091 Beijing, China.
Sci Total Environ. 2020 Nov 1;741:140141. doi: 10.1016/j.scitotenv.2020.140141. Epub 2020 Jun 17.
Hummocks (thúfur, pounus) are peculiar landforms usually formed by repeated freeze-thaw processes and differential frost heave, and are common in frost soil regions, especially in the Qinghai-Tibet Plateau. However, little is known about the response of δC in soil organic carbon (δC) to soil and climate properties in hummocks. The β value indicates the decomposition rate of soil organic carbon (SOC) in soil, and was obtained from the slope of the regression between the log10-transformed SOC concentration and δC in soil depth profiles. In this study, we investigated δC and SOC contents along a soil profile (0-60 cm), together with edaphic and climatic properties, both in hummocks and control plots (alpine grasslands) on the northeastern Qinghai-Tibet Plateau. Then, the variations in δC and β values, and the main factors affecting them, were analyzed. The results show that δC increases with soil depth, while SOC decreases both in the hummocks and control plots. However, β values in the hummocks were significantly (P < 0.05) higher than in the control plots while δC showed no difference between hummock and control. Redundancy analysis showed that altitude is the main control factor for δC and β in the hummocks. Climate type was the main factor affecting δC in the control plots, while mean annual precipitation and soil fractal dimension were the main factors controlling β. Overall, climate, rather than soil, is the key factor that affects the carbon turnover rate in the hummock in the northeastern QTP. The findings of this study will expand our understanding of the soil carbon cycle and δC changes, especially in the case of hummocks.
土丘（thúfur，pounus）是一种特殊的地貌，通常是由反复的冻融过程和差异冻胀形成的，在寒漠土地区很常见，尤其是在青藏高原。然而，人们对土丘中土壤有机碳（δC）对土壤和气候特性的响应知之甚少。β值表示土壤有机碳（SOC）在土壤中的分解速率，是通过土壤深度剖面中 SOC 浓度和 δC 的对数变换之间的回归斜率获得的。本研究在青藏高原东北部，对土丘和对照样地（高山草原）的土壤剖面（0-60cm）中 δC 和 SOC 含量以及土壤和气候特性进行了调查。然后，分析了 δC 和 β 值的变化及其主要影响因素。结果表明，δC 随土壤深度的增加而增加，而 SOC 在土丘和对照样地中都减少。然而，土丘中的 β 值显著（P<0.05）高于对照样地，而 δC 则在土丘和对照样地之间没有差异。冗余分析表明，海拔是土丘中 δC 和 β 的主要控制因素。气候类型是对照样地中 δC 的主要影响因素，而年平均降水量和土壤分形维数是控制 β 的主要因素。总体而言，气候而不是土壤是影响青藏高原东北部土丘中碳周转速率的关键因素。本研究的结果将扩展我们对土壤碳循环和 δC 变化的理解，特别是在土丘的情况下。
