宁夏农牧交错带土地利用变化对土壤质量的影响

Effects of land use changes on soil quality in agro-pastoral transitional zone in Ningxia, Northern China

在宁夏盐池县分别选取农田、弃耕地、天然草地、人工柠条林地和杨树林地5种土地利用类型作为研究样地,测定土壤理化性质指标,采用土壤质量综合技术指标,阐明中国北方典型农牧交错带土地利用变化对土壤质量的影响规律。结果表明:(1)土壤粗砂粒表现为弃耕地和天然草地显著高于农田、人工柠条林地和杨树林地(P<0.05),土壤细砂粒表现为杨树林地显著高于农田、弃耕地、天然草地和人工柠条林地(P<0.05),土壤极细砂粒和土壤黏粉粒均表现为农田和人工柠条林地显著高于弃耕地、天然草地和杨树林地(P<0.05)。土壤含水量、土壤pH值和土壤电导率表现为农田显著高于弃耕地、天然草地、人工柠条林地和杨树林地(P<0.05)。土壤有机碳含量表现为弃耕地和柠条林地显著高于农田、天然草地和杨树林地(P<0.05)。土壤全氮含量表现为农田显著高于弃耕地、天然草地、柠条林地和杨树林地(P<0.05)。(2)不同土地利用类型的土壤质量指标之间存在显著相关性(P<0.05)。其中,杨树林地各评价指标之间的相关系数最高,天然草地次之,农田、柠条林地较低,而弃耕地最低。(3)土壤质量综合得分大小顺序为:农田>弃耕地>0>草地>柠条林地>杨树林地。研究表明,对水浇农田实行保护性耕作和精细管理,并且农田弃耕后自然恢复成草地,有利于宁夏农牧交错带沙地土壤质量改善,但天然草地和人工林建设样地土壤质量较差。

In Yanchi County of Ningxia,five land use types including farmland,abandoned farmland,natural grassland,and afforested Caragana shrubland and poplar agroforestry land were selected as study sites.Soil physical and chemical properties were determined,and comprehensive technical indexes regarding soil quality were calculated in order to probe into the effects of land use changes on soil quality in agro-pastoral transitional zone in Ningxia,northern China.All the results are as follows.(1)Soil coarse sand was found to be significantly(P<0.05)greater in abandoned farmland and natural grassland compared with farmland,afforested Caragana shrubland and poplar agroforestry land;soil fine sand was found to be significantly(P<0.05)greater in afforested poplar agroforestry land compared with farmland,abandoned farmland,natural grassland and afforested Caragana shrubland;both of soil very fine sand and soil clay and silt were found to be significantly(P<0.05)greater in farmland and afforested Caragana shrubland compared with abandoned farmland,natural grassland and afforested poplar agroforestry land.Soil moisture content,soil pH and soil electrical conductivity were found to be significantly(P<0.05)greater in farmland compared with abandoned farmland,natural grassland,afforested Caragana shrubland and poplar agroforestry land.Soil organic carbon was found to be significantly(P<0.05)greater in abandoned farmland and afforested Caragana shrubland compared with farmland,natural grassland and afforested poplar agroforestry land.Soil total nitrogen was found to be significantly(P<0.05)greater in farmland compared with abandoned farmland,natural grassland,afforested Caragana shrubland and afforested poplar agroforestry land.(2)There was a significant(P<0.05)correlation between the above-mentioned soil quality indexes under land use types.The correlation coefficient between the evaluation indexes was found to follow the order of afforested poplar agroforestry land>natural grassland>farmland and afforested Caragana shrubland>abandoned farmland.(3)The soil quality comprehensive index followed the order of farmland>abandoned farmland>0>natural grassland>afforested Caragana shrubland>afforested poplar agroforestry land.It was concluded that the protective cultivation and intensive management on farmland,and the abandonment of cultivated farmland could facilitate the maintenance of soil quality,whereas the sandy natural grassland and afforested plantation could result in low soil quality in agro-pastoral transitional zone in Ningxia,Northern China.