【作者】 苏永中； 苏培玺；

【Author】 SU Yongzhong;SU Peixi;Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences;

【机构】 中国科学院寒区旱区环境与工程研究所；

【摘要】 退耕还林还草是防止水土流失、改善生态环境的一项重大举措。黑河流域中游边缘绿洲带土壤风蚀严重,生态环境脆弱,是中国北方沙尘暴的发生源地之一。该区域农田土壤为灌耕风沙土和灰棕漠土,结构松散,肥力低下,保水性能差,农作物生产依赖于高量的化肥和灌溉用水投入,资源利用效率低,退耕还草是合理利用水土资源、改善区域环境的适宜选择。对农田风蚀的观测表明,在春季大风天气,苜蓿地风蚀输沙量仅为春耕裸露农田的O.4%;退耕5年的苜蓿地较相邻农田土壤有机碳含量明显提高,表层（0²0 cm）土壤碳的固存率平均为0.47 mg·ha^-1·a^-1,表明中国北方大面积实施的退耕还林还草可以显著贡献于大气CO₂的固存;退耕苜蓿地较小麦和玉米地,分别减少灌溉量940 m³·ha^-1和4800 m³·h^-1,有明显的节水效应。更多还原

【Abstract】 Converting marginal farmland to forest or pasture is an important strategy to control the losses of soil and water resources and to improve regional environments.The marginal region of the oases in the middle reaches of Heihe River basin is a fragile ecoregion,where the farmlands have been suffering from serious soil erosion by wind and became one of the main source region of dust storm in northwest China.Agricultural soils are characterized by loose soil structure with high sand content and very low organic matter and nutrient level.Converting crops to perennial grass（alfalfa） is a rational alternative of land use pattern in this region.The observation of soil erosion by wind in the windy spring season during sandstorm events indicated that the sand transport rate in the 0—20 cm height in alfalfa field was only 0.4%of that in the spring-ploughed bare cropland.Soil organic carbon content increased significantly in the alfalfa field in comparison with the adjacent croplands.The carbon sequestration rate was,on average,0.47 mg·ha^-1·a^-1 following the converting crops to alfalfa,suggesting that the large-scale conversion of marginal croplands to perennial alfalfa in northwest China may contribute significantly to the sequestration of atmospheric CO₂.In comparison with spring wheat and corn,the assumption of irrigated water for alfalfa reduced by 940 m³·ha^-1 and 4800 m³·ha^-1,respectively,suggesting there is evident water-saving effect更多还原