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Chinese Journal of Applied Ecology ›› 2019, Vol. 30 ›› Issue (6): 1927-1935.doi: 10.13287/j.1001-9332.201906.001

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Soil organic carbon dynamics and the prediction of their spatial changes in response to anthropogenically introduced shrub encroachment in desert steppe of the Eastern Ningxia, China.

ZHAO Ya-nan1, DU Yan-yan1, MA Yan-ping1, ZHAO Yan-bing1, ZHOU Yu-rong1, WANG Hong-mei1,2,*   

  1. 1School of Agriculture, Ningxia University, Yinchuan 750021, China;
    2Mini-stry of Education Key Laboratory for Restoration and Reconstruction of Degraded Ecosystem in Northwest China, Yinchuan 750021, China
  • Received:2018-09-05 Online:2019-06-15 Published:2019-06-15
  • Supported by:
    This work was supported by the Ningxia Science-technology Support Plan (the Public-Benefit Plan 2015), the National Natural Science Foundation of China (31860677), and the Ningxia Higher Education Institutions First-class Discipline Construction Project (NXYLXK2017A01)

Abstract: With the 14-year enclosed grassland and the grazed grassland as control, the impacts of anthropogenic shrublands (Caragana korshinskii) with the different planting years (3, 12, 22 a) and planting spaces (2, 8, 40 m) on soil organic carbon (SOC) contents were examined in the desert steppe of Eastern Ningxia, China. We further analyzed the spatial pattern and heterogeneity of SOC in 0-40 cm soil layer of the grassland area with introduced shrubs. The results showed that SOC in C. korshinskii shrublands had an increase trend with increased planting years and decreased spaces. The mean SOC with different planting years and spaces was 42.7% and 32.8% more than that in grazing land, respectively. There was no significant difference of SOC between shrublands and the 14-year enclosed grassland. The increase trend of SOC decreased by 27.0% in 22-year planting shrubland. The SOC content of 0-40 cm soil layer varied from 0.21 g·kg-1 to 26.04 g·kg-1 (with a mean of 3.75 g·kg-1), and the coefficient of SOC variation ranged from 90.9% to 114.7%. The SOC in 0-5 cm and 15-40 cm soil layers fitted the optimal theory formulation of Gaussian model, while that in 5-15 cm soil layer fitted a spherical model. The ranges (A0) of spatial autocorrelation in the 0-5 and 5-15 cm soil layers were smaller (3.11, 3.00 km) than that in 15-40 cm soil layer (10.10 km). The nugget/sill C0/(C0+C) of SOC in 0-5, 5-15 cm soil layer was 0.2% and 16.3%, indicating a strong spatial correlation, while that in 15-40 cm soil layer was 36.9%, with a moderate correlation. The shrub introdution could significantly accelerate the accumulation and fixation of SOC in top 40 cm soil layer in degraded desert steppe, but also intensified the spatial heterogeneity and SOC fragmentation. The SOC content in the anthropogenic shrublands had no significant difference from that in the enclosed desert steppe (14 years). The SOC spatial heterogeneity and the degree of fragmentation were weakened and decreased with the increasing soil layer depth.