关中塿土堆垫层厚度空间分布特征及其影响因素

塿土堆垫层是关中农民长期农业生产过程中施用土粪并经耕作熟化形成的,其厚度可以表征塿土肥力水平,也能够反映人为活动对成土过程作用的强弱。开展塿土堆垫层厚度调查及其自然与人为影响因素分析,可为塿土养分保蓄及分类提供科学依据。本文在关中塿土分布区布设5 km×5 km网格样点,调查了273个塿土剖面堆垫层厚度并分析其空间分布特征;同时选取13个影响因子分析堆垫层厚度与自然及人为因素的相关性,并运用随机森林算法对各影响因素进行重要性排序。结果表明:关中地区塿土堆垫层厚度总体范围在14～130 cm,平均厚度为55 cm;其变异系数为34.28%,属中等变异程度;堆垫层厚度在东部的韩城、合阳和澄城(60～80 cm占优)一带及西部的陈仓、岐山和武功(60～70 cm占优)一带相对较高;堆垫层厚度与经纬度呈显著正相关,与坡度、温度和湿度呈显著负相关;堆垫层厚度与人口数量的增加呈正比,与人均耕地面积的减少呈反比;堆垫层厚度的最大值多出现在距离河流9～13 km范围中。本研究所筛选的13个影响因子对塿土堆垫层厚度的综合解释能力为64.36%,其重要性排序结果显示人均耕地面积变化对塿土堆垫层厚度的影响最...

Spatial Distribution Characteristics and Impact Factors of Cumulic Epipedon Thickness in Lou Soil of Guanzhong Region in Shaanxi Province

The cumulic epipedon of Lou soil is formed by dung stacking till slaking. The thickness of cumulic epipedon can reflect the fertility level of Lou soil and the effect of human activities on the soil forming process. The investigation on the thickness of cumulic epipedon and the analysis of its natural and human factors can provide scientific basis for the nutrient-holding capacity and the classification of Lou soil. In this study, grid sampling sites (5 km × 5 km) were designed in the Guanzhong region to investigate the thickness and spatial distribution characteristics of cumulic epipedon using 273 profiles of Lou soil. At the same time, 13 influencing factors were selected to analyze the correlation between the cumulic epipedon thickness and the natural and human factors, with a quantitative analysis of their importance by random forest regression. The thickness of the cumulic epipedon in Guanzhong region ranged from 14 to 130 cm, with an average thickness of 55 cm. Its coefficient of variation was 34.28%, belonging to the medium degree of variation. It was relatively high distributed in Hancheng, Heyang and Chengcheng (60-80 cm dominant) areas in the east and Chencang, Qishan and Wugong (60-70 cm dominant) areas in the west. The thickness of cumulic epipedon had a significant positive correlation with latitude and longitude, and a significant negative correlation with slope, temperature and humidity. The influence of human factors was directly proportional to the increase of population and inversely proportional to the decrease of per capita cultivated land area. The maximum thickness of cumulic epipedon mostly appeared in the range of 9-13 km from the river. The comprehensive interpretation of the 13 influencing factors was 64.36% for the thickness of cumulic epipedon. The results of importance ranking showed that the change of per capita cultivated land area had the most significant effect on the thickness of the cumulic epipedon, followed by the change of population. The thickness of cumulic epipedon in the Guanzhong region was higher in the east and west, and slightly lower in the middle, and the high points were distributed sporadically. The formation and distribution of the cumulic epipedon were more deeply affected by human factors than the "five soil forming factors", especially gradually increased with the development of productivity in the past hundred years.