Statistical analysis of soil moisture at grassland in the Horqin Sand Land

Abstract

Firstly, based on the observed data of soil moisture (SM) at grassland from May to September in 2009~2012, we analyzed the variation and statistical characteristics of SM from 0 to 150 cm in growing seasons (from May to September) at grassland of Horqin Sand Land by statistical analysis and the test method of normal distribution, and the normality of SM in different soil layer and different month were tested by Skewness, Kurtosis test method. Secondly, based on the SM of obeying normal distribution, we obtained the estimates and the confidence interval of the mean and variance for the normal distribution. The results indicated that: (1) The SM of grassland at the same soil layer and same month passed the hypothesis testing of normal distribution at the significance level of α = 0.1, but the SM of grassland at different months did not pass this hypothesis testing; (2) The value of SM at grassland ranged from 2%∼10%; The standard deviation of SM at grassland was 1∼5; The variation coefficient of SM at grassland was between 0∼1; (3) Influenced by precipitation, SM for grassland was higher in July, and significant different from other months in the growing season (from May to September); The estimates and confidence interval for the mean and variance of SM at grassland in July were significantly different from other months of the growing season; The variation of SM at grassland with month increased firstly and then decreased. (4) SM of grassland was lower at 0∼10 cm and different from other soil layer; With the increasing of soil depth, SM of grassland presented a “adverse S″ type.