Scale effects of spatial variations in SOM and STN in semi-arid regions: A case study of Yan'an
WANG Peng1(), ZHAO Jun1(), LIU Tuo1, ZHOU Yi-Fan2, WEI Jin-Ping1, WANG Lei1
1. Xi'an Center of China Geological Survey Northwest China Center for Geoscience Innovation,Xi'an 710054,China 2. Xi'an Institute of Prespecting and Mapping,Xi'an 710059,China
Taking high-density sampling data as a dataset, the sampling spatial distribution scenarios on different scales were simulated through resampling analysis. Spatial analysis methods, such as Moran's I index, semi-variance function value, and fractal dimension FD, were used to explore the scale effects of spatial variations in soil organic matter (SOM) and soil total nitrogen (STN) and to analyze the conversion of influencing factors between different scales. The results are as follows. With an increase in scale, the spatial agglomeration decreased, and the spatial variation of SOM and STN in general increased first and then tended to be stable. By contrast, the random variation decreased gradually and the structural variation increased first and then decreased as the scales increased. The spatial variation generated on small scales consisted of a large proportion of random variation and a small proportion of structural variation, while the opposite is true on large scales. Different influencing factors had different distinguishing degrees for the spatial variations in SOM and STN. Their distinguishing degrees were in the order of height<factors such as soil type, vegetation index, annual average temperature, and humidity<precipitation. The influencing factors of the spatial variations in SOM and STN had scale effects. Specifically, with an increase in scale, the random variation caused by small-scale factors decreased gradually, while the structural variation caused by large-scale factors increased first and then weakened until the large-scale factors were transformed into relatively small-scale factors. The coordination mechanism of the effects of each factor on the SOM and STN contents was quite different between different scales, causing the random and structural variations to fluctuate between different scales. As a result, the spatial variations showed the law of decreasing first and then tending to stabilize.
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WANG Peng, ZHAO Jun, LIU Tuo, ZHOU Yi-Fan, WEI Jin-Ping, WANG Lei. Scale effects of spatial variations in SOM and STN in semi-arid regions: A case study of Yan'an. Geophysical and Geochemical Exploration, 2022, 46(4): 1011-1020.
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