黄土丘陵区旱作枣园覆盖耕作土壤水热耦合效应与调控

The planting area of dryland jujube developed rapidly in loess hilly region since since the Grain for Green projet was implemented in 1999. However, because of drought and water shortage coupled with barren soil and popular application of traditional clean tillage method in the jujube orchard, the capacity of soil water storage, evaporation restraint, and anti-erosion are very poor. Moreover, the economic and ecological benefits of the jujube orchard are low. In this study, based on dryland jujube orchard production and actual resources of soil and water, the dynamic characteristics of soil water and heat under the condition of mulching and cultivation technology was investigated by the method of the field site fixed observation and the indoor numerical simulation. The purpose of the study is to illustrate the regulation effect of mulching and cultivation technology on slope soil water and heat, to reveal the mechanism of soil water and heat coupling transport, to quantify the water consumption and water use efficiency of jujube trees, to establish the technology model of cultivation and mulching based on the theory of rainfall resources efficient utilization, and to realize the simultaneous improvement of economic and ecological benefits in the jujube orchard. This study is very significant and has an important application prospect for promoting jujube farmers income and protecting the sustained and healthy development of the Grain for Green projet in loess hilly region.

国家退耕还林（草）工程实施以来，黄土丘陵区旱作红枣面积发展迅猛，但由于干旱缺水与土壤贫瘠，加之现有旱作枣园普遍盛行传统清耕技术，导致坡面土壤蓄水抑蒸保墒抗蚀效果差，经济效益与生态效益低下。本研究立足于黄土丘陵区旱作枣园生产和资源实际，采用野外坡面小区定位观测试验和室内数值模拟相结合研究方法，系统研究旱作枣园不同覆盖耕作技术下坡面土壤水分和温度动态变化特征，阐明不同覆盖耕作技术对坡面土壤水分和温度的调控效果，揭示坡面土壤水热耦合运移机制，探求不同覆盖耕作技术对红枣生长和产量的影响，量化旱作枣园枣树耗水量和水分利用效率，建立基于降水资源高效利用的覆盖耕作技术模式，同步提高旱作枣园经济效益和生态效益。该研究对于促进黄土丘陵区农民增收，保障国家退耕还林（草）工程持续健康发展具有重要借鉴意义和应用前景。

退耕还林（草）工程实施以后，黄土丘陵区经济林发展迅猛，成为区域经济发展的主导产业，了解该区不同土地类型和技术措施下的土壤水热状况是制定合理开发利用方式的重要前提，因此，揭示黄土丘陵区典型土地利用方式的土壤水热特征及其耦合效应，对于实现区域坡地资源的高效持续利用具有重要的理论和实践意义。本研究基于多年连续试验，探明了枣园不同覆盖工程组合措施的集水保墒效益，土壤水分亏缺状况显著降低。阐明了不同枣农复合系统土壤水分和产流产沙调控效应，发现枣树-黄花菜和枣树-油菜复合系统显著减少了地表径流量和产沙量，体现了显著的水土保持效益。揭示了不同坡地利用方式土壤水热变化特征，发现梯田土壤含水量和土壤温度显著（p<0.05）高于坡地，保墒增温效果显著；采用小波分维估计法和近似熵理论揭示了不同坡地利用方式土壤水热的复杂性，发现红枣林土壤水热变化过程较为复杂，而玉米梯田减小了土壤水热变化的复杂程度，有利于保持土壤水分的稳定性，并调节土壤温度；构建了一维垂向土壤水热耦合运移数值模型，模拟值与实测值的决定系数R2为0.8581～0.9901，均方根误差RMSE和平均绝对误差MAE的平均值分别为0.7719%和0.6856%。本研究所得结论可为黄土丘陵区坡地利用结构优化和土地资源高效持续利用提供科学依据。