Spatial Distribution Characteristics And Influencing Factors Of Organic Matter In Black Soil Region Of Songnen Plain

The Songnen Plain black soil region is an important commercial grain production base in China,with complex and changeable terrain.In recent years,affected by unreasonable production methods,the soil organic matter content has been declining,and the black soil layer is seriously degraded.It is urgent to protect the black soil resources and master the spatial distribution of the research region organic matter and its influencing factors are the basis for protecting black soil resources.Therefore,it is particularly important to explore the spatial variability and influencing factors of soil organic matter in this region.The results of this study can provide data support for the development of precision agriculture,modern agriculture and soil nutrient management in this region.In view of this,the three scale nesting regions in the black soil region of the Songnen Plain were taken as the research objects.The spatial distribution characteristics and variation law of soil organic matter in 0?20 cm and 20?40 cm soil layers were investigated using the combination of classical statistics,geostatistics and multiple fractal methods.The joint multifractal method was used to analyze the correlation of spatial variability of soil organic matter in 0?20 cm and 20?40 cm soil layers.The effect of elevation,slope,aspect,land use pattern,soil type,multi-year average annual temperature and multi-year average annual rainfall on the soil organic matter content of 0?20 cm and 20?40 cm soil layers were determined by analysis of variance and correlation coefficient method.?1?Classical statistical analysis showed that the average values of soil organic matter in different soil layers at three scales were 43.10 g·kg^-1,43.31 g·kg^-1,57.53 g·kg^-1,52.97 g·kg^-1,57.98 g·kg^-1and 51.83 g·kg^-1,all belong to the first level,and the coefficients of difference were 0.207,0.281,0.443,0.474,0.448 and 0.488,which were all moderate variations.At the same scale,the variation of soil organic matter in 20?40 cm soil layers was greater than that in 0?20 cm soil layers,and the variation degree of soil organic matter in different soil layers increased with the increase of scale.?2?Geostatistical analysis showed that the coefficient of determination R² of the semi-variance function model of different soil layers under isotropy increased with the increase of scale,and the range was also positively correlated with the scale.The soil organic matter in the small scale 0?20 cm soil layer and the large scale 20?40 cm soil layer showed strong spatial correlation,and the rest showed moderate spatial correlation.The anisotropic mesoscale and large scale 0?20 cm soil layer and 20?40 cm soil layer had strong spatial variability in the north-south direction and northeast-southwest direction.The spatial variation in the direction and the southeast-northwest direction is relatively small.The direction of spatial variability of soil organic matter in small scale 0?20 cm soil layers and 20?40 cm soil layers was not consistent.The mesoscale and large scale 0?20 cm soil layer and 20?40 cm soil layer soil organic matter decreased gradually from northeast to southwest,and the small scale 0?20 cm soil layer soil organic matter content gradually increased from northwest to southeast direction Decreased,the soil organic matter content of the 20?40 cm soil layer gradually decreased from northeast to southwest.?3?Multifractal analysis showed that the soil organic matter in the 0?20 cm soil layer and 20?40 cm soil layer under the three scales had multifractal char acteristics.The shapes of the multifractal spectrum of soil organic matter under mesoscale and large scale in 0?20 cm soil layer and 20?40 cm soil layer were left hook shape,and its spatial variability was derived from its low value information.The spatial variability of soil organic matter in 0?20 cm soil layer comes from its low value information,and the spatial variability of soil organic matter in 20?40 cm soil layer comes from its high value information.The spatial variability of soil organic matter in the 20?40cm soil layer at three scales was higher than that in the 0?20 cm soil layer.Joint multifractal showed that the correlation coefficients of the singular indexes corresponding to the soil organic matter content in the soil layers of 0?20 cm and 20?40 cm at the three scales were 0.6872,0.9428,and 0.8801,respectively,which had a high correlation.?4?The content of soil organic matter in the 0?20 cm and 20?40 cm soil layers of the black soil region of the Songnen Plain was mainly affected by elevation,soil type,land use type,and average temperature for many years.However,soil organic matter content was not significantly affected by slope,aspect,and average rainfall over many years.The content of soil organic matter in different layers of soil increased with the elevation and the decrease of the average temperature for many years.The order of the organic matter content of the two soil layers under differ ent soil types was:swamp soil>peat soil>dark brown soil>meadow soil>black soil>chernozem soil>paddy soil.The order of soil organic matter in the 0?20 cm soil layer under different land use types was:unused land>forest land>grassland>cultivated land>urban,and the order of the soil organic matter content in the 20?40 cm soil layer was:unused land>forest land>grassland>city>cultivated land.