陇东黄土高原农田土壤湿度演变对气候变化的响应

以甘肃省庆阳市西峰区为例,利用近50a气象观测资料和近20a的土壤湿度观测资料,分析全球气候变暖背景下陇东主要气象要素及土壤湿度的变化特征,研究了气候变化对土壤湿度的影响。50a来陇东气温呈波动上升趋势,降水量呈波动减少趋势。1991—2010年陇东各层土壤湿度总体上均呈现出下降趋势,春季是土壤湿度减少最明显的季节,夏季土壤湿度变化趋势与春季具有类似规律,但变化率明显低于春季。秋季浅层土壤湿度呈下降趋势,深层呈上升趋势。就表层土壤湿度而言,各季土壤湿度与该季气温均为负相关,与降水量呈正相关。而对较深层土壤而言,土壤湿度与气温、降水的相关关系因季节而异。潜在蒸散量对土壤湿度的影响月份和年际变化均呈现出反位相的特点,基本呈同步变化趋势。通过对农田土壤水分演变特征及其影响因素进行分析,为进一步理解土壤水分的演变,合理利用气候资源,调整农业生态布局,积极应对气候变化提供决策方面的参考。

Responses of Soil Moisture Evolution in Cropland to Climate

In a case study of Xifeng City on the Longdong Loess Plateau,climate change trends and its effects on soil moisture,as well as the evolution of soil moisture were analyzed based on the 50-year climate data and the 20-year observation data of soil moisture.Results show that temperature increased and rainfall decreased in the recent 50 years.From 1991 to 2010,soil moisture in Longdong presented a downward trend on the whole.In spring,soil moisture decreased more severely and in summer,soil moisture had a similar trend,but the rate of change was significantly lower than that in spring.In fall,soil moisture in shallow soil layer showed a downward trend,while the deep soil presented a rise trend.For topsoil,soil moisture in each season was negatively correlated with temperature and positively correlated with precipitation.For deeper soil layer,the correlations of soil moisture with temperature and precipitation depended on season.The effects of potential evapotranspiration on soil moisture were characterized by an antiphase monthly and annually,and the basic trends were synchronized.The analyses of soil moisture evolution and its influence factors may provide some references to the decision making for understanding soil moisture evolution,rationally using climatic resources,adjusting agricultural and ecological patterns and positively coping with climate change.