人工降雨条件下不同坡长和覆盖度对氮素流失的影响

用植被覆盖度(20%,45%,60%,90%)和坡长(1,2,3,4,5m)作为可变因素,设定固定雨强2.0mm/min进行室内模拟降雨,研究氮素的流失特征,探索坡长、覆盖度和径流对氮素流失的影响。通过对试验数据的分析,结论为:(1)相同覆盖度,不同坡长全氮(TN)流失量随时间延长而逐渐增加,并且随着坡长的增加,流失量逐渐增大,但径流中总氮的浓度变化差异不明显。硝态氮(NO3--N)和铵态氮(NH4+-N)流失量的变化与TN较为相似,流失浓度随着时间变化主要表现为径流前期浓度较高,随着降雨时间的延长,浓度逐步降低并最终趋于稳定。(2)降雨过程中,径流中的氮流失主要以溶解态的氮为主,并以NO3--N比NH4+-N含量高,但是随着降雨时间的延长,不溶性氮的比例也会有所增加。(3)径流量对各形态氮的流失影响十分明显,植被覆盖度和坡长分别与TN、NO3--N的流失量呈显著负相关和显著正相关。

Effects of Different Slope Length and Vegetation Coverage on Nitrogen Loss in Sloping Land under Artificial Simulated Rainfall

In order to investigate effects of under different slope length(1,2,3,4,5 m) and vegetation coverage(20%,45%,60%,90%) on runoff producing processes and nitrogen loss,a simulated rainfall experiment was conducted.The results showed that:(1)Under the same coverage and different slope length,the loss content of TN,NH+4-N and NO-3-N gradually increased with rainfall duration,with increasing of the slope length,the greater N’s losing quantity of full state,but the concentration of TN in runoff were more steady and changed little.The changing trends of NH+4-N and NO-3-N concentration in runoff were high in early stage,and then reduced with increasing time,and gradually became stable for the final rainfall phase.(2)Dissolved nitrogen was the main form in N loss,while NO-3-N was the main component in dissolved nitrogen,and the content of NO-3-N was significantly higher than NH+4-N,the loss percentage of undissolved nitrogen increased with increasing time in runoff.(3)Runoff volume had significant effects on each forms of nitrogen loss,furthermore,both slope length and vegetation coverage had a positively and negatively correlation with the loss amounts of TN and NO-3-N,respectively.