Hyperspectral features of soil organic matter content in South Xinjiang.

The organic matter content in soil is a mainly index of nutrient fertility in soil and an important factor of spectral characteristics of soil.In this paper,spectral characteristics of meadow soil,anthropogenic-alluvial soil,saline soil,aeolian sandy soil,paddy soil rice soil and alluvial soil in southern Xinjiang and their relationship with soil organic matter were studied through field sampling and lab physical and chemical analysis and spectrum tests,and the pre-and-post changes,ratio and difference of spectral reflectance ratio after removing soil organic matter were compared by transform in different forms of soil spectral through differential technology and regression analysis.The results showed that the spectrum reflectance increasing significantly either over all wavebands or ultraviolet,visible,near-infrared bands after the soils were cleared organic matter in soil and the greatest change appeared in band 360-380 nm,the secondary change appeared in band 380-760 nm of the average spectrum reflectance,and the spectrum reflectance of anthropogenic-alluvial soil and swamp soil were some different,the changes in the spectrum reflectance of anthropogenic-alluvial soil was larger significantly than swamp soil after the soils were cleared organic matter either over all wavebands or in band 380-760 nm,760-1 072 nm,but lower in band 360-380 nm.The correlation on spectrum reflectance with organic matter content in soil has some difference through mathematical transformation(reciprocal,logarithm,differential) by minus operation and ratio operation.The band 600.51nm and 539.21nm were characteristic bands of the reciprocal,logarithm and 1-order differential respective on spectrum reflectance with organic matter content in soil.Before mathematical transformation,the spectrum reflectance with organic matter content in soil was negative correlation;after reciprocal transformation and logarithmic transformation,the correlation was changed to positive or negative respective and the correlation coefficient increase in wave band 360-520 nm and decrease in wave band 520-1 072 nm respective,but the change range of reciprocal transformation was larger than logarithmic transformation;after 1-order differential transformation,the correlation was not single positive or negative and the correlation coefficient has large fluctuation,no regularity and increase only in some individual wave band.Regression analysis of spectrum reflectance with organic matter content in soil was done and the results showed that spectral reflectance and its 1-order differential transformation can predict organic matter content in soil and the precision is 72.3% in wave band 600.51nm used spectral reflectance and 87.0% in wave band 539.21 nm used 1-order differential transformation of spectral reflectance.The conclusion was suggested spectrum reflectance with organic matter content in soil has better correlation either over all wavebands or ultraviolet,visible,near-infrared bands and the spectral reflectance and its 1-order differential transformation can predict organic matter content in soil of different types in southern Xinjiang.