大气CO2浓度升高和施氮对棉田土壤理化性质及微生物区系的影响

针对耕地非农转化过程中产生的一系列社会问题,采用参与性农户调查方法,对西部欠发达地区西宁市郊区5个样本村190户农户进行了随机入户调查。根据城市开发进程、到市区距离和种植类型等条件,将调查样本村分为近郊城区化农村、近郊农村和远郊农村,就农户对耕地非农转换的基本认知及耕地非农转换的经济、社会和环境价值感知进行分析。结果表明:耕地征用后农户能理性感知和判别耕地非农转换价值,并普遍认为失去耕地后生活费用增加、生活保障降低、收入来源和就业机会少;感知主要受耕地数量、区位条件、耕地开发阶段等因素的影响;处于不同区位条件的农户对耕地非农转换的价值感知存在差异性,城区化农户已逐渐适应城市生活,近郊农户的非农转换经济和社会感知压力最大,远郊农民也感知经济和生活保障压力,但更希望能通过打工增加收入。

Influence of elevated CO2 and nitrogen supply on cotton field soil properties and microbial flora

To illuminate influence of elevated CO₂ and nitrogen supply on cotton field properties and microbial flora in the plot experiment, this study investigated organic carbon, total nitrogen, bicarbonate ion, pH, total salt and soil bacteria, soil fungi, soil actinomycetes under ambient CO₂(360 μmol·mol^-1) and elevated CO₂ (540 and 720 μmol·mol^-1) at 4 nitrogen levels (0, 150, 300 and 400 kgN/hm²). The results showed that, organic carbon, total nitrogen and pH at a soil depth of 0-40 cm tended to decrease elevated CO₂(720 μmol·mol^-1) at different nitrogen levels, but less effects on soil bicarbonate ion and total salt were found. Both bacteria population at a soil depth of 0-40 cm and actinomycetes population at 0-20 cm were enlarged, but fungi population at 20-40 cm soil depth tended to decrease under elevated CO₂ concentration (540 and 720 μmol·mol^-1) at different nitrogen levels.