红壤坡地柑桔园长期试验下水沙动态变化特征分析

以红壤清耕柑桔园坡地为对象,研究其长期定位试验下2001—2015年径流和泥沙流失量的动态变化过程以及坡面水沙与降雨关系的变异特征。结果表明:幼树期是红壤清耕柑桔园水土保持防治的关键期,该时期的土壤侵蚀程度达到极强烈,而盛果期侵蚀强度可降低到区域土壤容许流失量以下。柑桔树从幼树期、初果期到盛果期,坡面年径流量和土壤侵蚀模数均呈显著幂函数下降趋势,在盛果期趋于稳定。果树坡面水沙与降雨的关系均在第4年发生了突变,而裸露坡面水沙与降雨关系没有发生突变。柑桔园各年的减沙效益均大于减水效益,减流、减沙效益均随着时间表现出先快速增加后维持相对稳定的指数函数关系,这表明免耕果树的减流、减沙效益具有很大的时间变异性,不仅可通过减水来减沙,而且可通过改变水沙关系来减沙。研究结果将为果园水土保持措施效益评估提供依据,为水土保持措施的合理配置提供参考。

Dynamic Characteristics of Soil and Water Loss Under Long-term Experiment in Citrus Orchard on Red Soil Slope

The citrus orchard slope and bare control slope were used as the research objects, the long-term dynamic processes of runoff and sediment yield and the variation of the relationship between runoff and sediment were studied based on the observation data from 2001 to 2015. The results showed that the annual runoff and soil erosion modulus of citrus trees slope decreased significantly from sapling stage, early fruit stage to full fruit stage, and tended to be stable in the full fruit stage. Sapling period was the key period of soil and water conservation in red soil orchard. The soil erosion intensity could be very strong in this period, while the soil erosion intensity could be reduced to below the allowable loss of soil in the full fruit period. The relationships between the runoff and the sediment and rainfall dramatically changed in the fourth year, while the relationships between the runoff and the sediment and rainfall of the bare slope maintained. The benefit of sediment reduction in citrus orchards was greater than that of runoff reducing in each year, and the benefits of runoff and sediment reduction increased rapidly and remained relatively stable over time, showing an exponential function. It meant that the benefits of runoff reduction and sediment reduction of fruit trees were very time variable, reduced sediment by reducing runoff as well as reduced sediment by changing the relationship between runoff and sediment. The results would provide a basis for evaluating the benefits of soil and water conservation measures in orchards, and provide a reference for the rational allocation of soil and water conservation measures.