Spatial Variability of Soil Moisture at Different Scales in Sandy Loam in Northern Henan Province北大核心CSCD

Objective]Soil moisture plays an important role in ecosystem function and hydrological processes. This paper investigated the hieratical distribution of soil moisture at different scales over a maize field.Method] The studied site was a 50 m×50 m plot at the Experiment Station of Chinese Academy of Agricultural Sciences in Xinxiang, Henan province. We measured soil moisture in 0~100 cm soil from 36 locations at 10 m×10 m and 2 m×2 m scale, respectively.Result]Geostatistical analysis revealed that the soil moisture was normally distributed and its confidence level at every scale was higher than that of logarithmic normal distribution. The value of the confidence level decreased as the sampling scale increased, and the difference between average soil moisture content at fine scale and moderate scale was smaller than the difference between moderate scale and large scale. In general, the confidence interval, standard deviation and coefficient of variation of the soil moisture increased with sampling scale. At large scale, the semi-variance function increased with lag distance, while at small and moderate scale, the variation function appeared to be independent of the lag distance. To achieve the same confidence level and accuracy in estimating soil moisture, the number of samples needed to be taken from the field increased with sampling scale. We also found that in estimating soil moisture, the number of samples needed to be taken depended on the required accuracy more than on the confidence level.Conclusion]The probabilistic distribution and statistical characteristics of soil moisture in the field was scale-dependent. In estimating soil moisture, the number of sampled taken from the field needs to consider the scales to which the measured data will be applied. © The Author(s) 2019.