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在长沙市宁乡超大蔬菜基地,以面积为239.5 hm2的蔬菜地为试验区,随机采集了329个土壤耕层(0~20 cm)样品,应用地统计学分析了土壤铵态氮、硝态氮、有效磷的空间变异特征,并应用克里格插值方法绘制了土壤三种有效养分的空间分布图。为了使数据更好地符合正态分布,我们对它们进行了logit转化。通过趋势分析,我们发现铵态氮不存在明显的空间趋势,硝态氮和有效磷存在二阶空间趋势。地统计分析结果表明,数据经logit转化和必要的趋势去除后,铵态氮和硝态氮表现为中等空间自相关性,有效磷表现出较强的空间自相关性。铵态氮的半方差函数图符合Matérn模型,硝态氮和有效磷的半方差函数图符合Stein的Matérn模型。它们的变程分别为144 m、592 m、168 m。研究区铵态氮空间分布破碎化程度较高,硝态氮和有效磷的空间分布具有明显的阶梯状趋势。
A total of 329 soil tillage (0 ~ 20 cm) samples were collected from a vegetable field with an area of 239.5 hm2 in a large vegetable base in Ningxiang City, Changsha City. Geostatistics was used to analyze soil ammonium nitrogen and nitrate state Nitrogen and available phosphorus, and the spatial distribution of three effective nutrients in soil was drawn by using Kriging interpolation method. To make the data better conform to the normal distribution, we logit them. Through the trend analysis, we found that there is no obvious spatial trend of ammonium nitrogen, nitrate nitrogen and available phosphorus there is a second-order spatial trend. Geostatistical analysis showed that after the data was logit transformed and the necessary trend was removed, the ammonium and nitrate nitrogen showed medium spatial autocorrelation, and the available phosphorus showed strong spatial autocorrelation. The semivariogram of ammonium nitrogen conformed to the Matérn model and the semivariogram of nitrate nitrogen and available phosphorus fitted Stein’s Matérn model. Their ranges are 144 m, 592 m, 168 m respectively. The spatial distribution of ammonium nitrogen in the study area is highly fragmented, and the spatial distribution of nitrate nitrogen and available phosphorus shows obvious ladder-like trend.