Dynamic changes of nitrogen in precipitation in lower reach of Liaohe River Plain
下辽河平原降雨中氮素的动态变化

To understand the effects of nitrogen(N) in precipitation on agroecosystems,the precipitation samples at the Shenyang Ecological Station located in lower reach of Liaohe River Plain were collected from 2004 to 2006,and their N forms and amounts were measured.The results showed that the N amount in precipitation had an obvious seasonal change,being the highest in summer due to the higher concentrations of NH4 -N in precipitation and atmosphere.The proportions of dissolved organic nitrogen(DON) and NO3--N to total nitrogen(TN) in precipitation were all about 24%,and the annual N flux imported to the agroecosystems by wet deposition was more abundant in recent three years than 20 years ago.The N amount in precipitation in 2005 was increased by one time,compared with that in 1985.On average,the N import from precipitation in 2004-2006 accounted for 28.3% of the applied fertilizer N,suggesting that the N input from precipitation had greater effects on agroecosystem.