No significant changes in topsoil carbon in the grasslands of northern China between the 1980s and 2000s.

Journal: The Science of the total environment
Published Date: Dec 27, 2017

Abstract

The grasslands of northern China store a large amount of soil organic carbon (SOC), and the small changes in SOC stock could significantly affect the regional C cycle. However, recent estimates of SOC changes in this region are highly controversial. In this study, we examined the changes in the SOC density (SOCD) in the upper 30cm of the grasslands of northern China between the 1980s and 2000s, using an improved approach that integrates field-based measurements into machine learning algorithms (artificial neural network (ANN) and random forest (RF)). The RF-generated SOCD averaged 5.55kgCm in the 1980s and 5.53kgCm in the 2000s, and the change ranged from -0.17 to 0.22kgCm at the 95% confidence level, suggesting that the overall SOCD did not vary significantly during the study period. However, the change in SOCD exhibited large regional variability; the topsoil of the Inner Mongolian grasslands experienced significant C loss (4.86 vs. 4.33kgCm), while that of the Xinjiang grasslands exhibited an accumulation of C (5.55 vs. 6.46kgCm). Furthermore, the topsoil C in the Tibetan alpine grasslands remained relatively stable (6.12 vs. 6.06kgCm). A comparison of the different grassland types indicated that SOCD significantly decreased in typical steppe, whereas it increased in mountain meadow, and remained stable in the other grasslands (alpine meadow, alpine steppe, mountain steppe and desert steppe). Climate change could partly explain the changes in the SOCD of the different grassland types. Increases in precipitation could lead to SOC accumulation in temperate grasslands and SOC loss in alpine grasslands, while climate warming is likely to cause SOC loss in temperate grasslands. Overall, our study suggests that the grasslands of northern China remained a neutral SOC sink between the 1980s and 2000s.

Authors

  • Shangshi Liu
    State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China.
  • Yuanhe Yang
    State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
  • Haihua Shen
    State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China.
  • Huifeng Hu
    State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
  • Xia Zhao
    Stony Brook University, Stony Brook, NY.
  • He Li
    National Soybean Processing Industry Technology Innovation Center, Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology and Business University Beijing 100048 China lihe@btbu.edu.cn liuxinqi@btbu.edu.cn.
  • Taoyu Liu
    State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China.
  • Jingyun Fang
    State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China; Department of Ecology, Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China. Electronic address: jyfang@urban.pku.edu.cn.

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