耕地土壤有机质与全氮空间变异性对粒度的响应研究

Spatial Variability Response of Farmland Soil Organic Matter and Total Nitrogen to Sampling Grain Size

为有效揭示土壤空间变异性的尺度效应,为土壤采样设计提供科学依据,以黄土台塬区耕地土壤有机质(SOM)和全氮(STN)为例,利用空间自相关、半方差函数及分形维数分析了不同采样粒度条件下土壤属性的空间结构变化规律。结果表明,研究区耕地SOM和STN的平均质量比分别为14.79 g/kg和0.78 g/kg;随采样粒度增大,SOM变异系数基本未变,STN则表现总体增加;其空间自相关性减弱,由随机因素所引起的空间变异性逐渐增强,导致结构变异比重趋于减小;SOM和STN空间异质性随粒度的变化并非简单线性关系,而表现出先增后减的倒U型变化。耕地SOM和STN的空间分布呈北高南低,SOM含量总体中等偏下,而STN含量较低,耕作时应适当增加氮素补充。

To effectively reveal scale effect of soil attributes and provide information for sampling design, the spatial variability response rules of soil organic matter and total nitrogen to sampling grain size were identified by spatial autocorrelation, semi-variogram and fractal dimension in Loess Plateau, China. The results showed that the average content of SOM and STN were 14.79 g/kg and 0.78 g/kg, respectively. With the sampling grain size increasing, the coefficient of variation of SOM had basically not changed, but that of STN showed a gradually elevated trend. In addition, the spatial autocorrelation of SOM and STN was weakened and their spatial variability from random factors became much stronger. Meanwhile, the relationship between spatial variability and sampling grain size was not linear, but a reverse ＂U＂ type changing trend. The spatial distribution of SOM and STN concentration exhibited higher in the north and lower in the south of study area. SOM content was at the mid-low level, but STN content was under the normal level which led to much more nitrogen needed in the future.