JOURNAL OF NATURAL RESOURCES ›› 2016, Vol. 31 ›› Issue (12): 2099-2110.doi: 10.11849/zrzyxb.20160084

• Resource Evaluation • Previous Articles     Next Articles

Spatial Characters of Soil Organic Matter withMulti-sampling Density

CHEN Yang1, QI Yan-bing1, 2, WANG Yin-yin1, HUANG Biao2, LIU Jiao-jiao1, ZHANG Liang-liang1   

  1. 1. College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China;;
    2. Nanjing Institute of Soil Science, CAS, Nanjing 210008, China
  • Received:2016-01-21 Online:2016-12-20 Published:2016-12-20
  • Supported by:

    Special Foundation of National Science and Technology Basic Work Project of China, No. 2014FY110200A08.

Abstract:

The spatial variation of soil properties is a function of spatial scales. The spatial structure of soil properties in special scale can be discovered with single sample density, however, the whole variation could be discovered with multiple sample densities. The study area locates in Zhangjiagang County, which is a part of Yangtze River delta. Soil organic matter (SOM) is one of the important issues in global change research, thus in this paper the top SOM content in fertilized area is studied. Four hundred and thirty one samples were collected as the fundamental data, 11 levels of density or scale were designed with grid centroid sampling method, then classic statistics, semi-variance function, Moran’s I, spatial fractal dimensions and Kriging interpolation were explored to investigate the variation of SOM in spatial structure, randomness and spatial patterns at different sampling densities. The results shows: There is a low influence of sampling density on SOM variation coefficient. The variation coefficients of SOM at 11 sampling densities are among 21.70%-23.12%, which belongs to the moderate variation. With the decrease of the sampling density or the increase of scale unit, the corresponding ratio of nugget/sill falls from 37.52% to 18.70%, fractal dimension falls from 1.838 to 1.714, and the Moran’s I index increases from 0.485 to 0.857, which indicates the components of spatial structure variation is increasing and spatial correlation is gradually enhanced. The content of SOM shows decreasing trend from southwest to northeast. The spatial pattern of SOM content becomes simple with the decrease of sampling density since more and more details in micro-areas are ignored. In general, the model inference accuracy of SOM is reliable and the spatial character is stable when the sampling density is lower than 0.179 sample per km2. In consideration of science and economy, it can be concluded that the density of 0.179 sample per km2 can reflect the spatial randomness and structure of SOM in the study area, and this density can be regarded as the best sampling density. The paper takes sampling densities as cases to reveal the multiple spatial scale characteristics of SOM, and provides a helpful reference for hierarchical analysis of soil properties.

Key words: sampling density, scale, soil organic matter, spatial variability

CLC Number: 

  • S153