中文摘要：

用Bremner法测定了长期（16a）定位的不同土地利用方式（水田、旱地和林地）下潮棕壤有机氮各组分的含量。结果表明：在O～60cm土层，3种土壤有机氮均以非酸解性氮为主，且酸解性全氮及酸解各组分氮含量及其占全氮的比例总体上以表层土壤（0～20cm）为最高。0～60cm土层土壤酸解性全氮含量及0～40cm土层土壤酸解各组分氮含量均随土层深度增加而下降，但0～60cm土层土壤酸解性全氮及其各组分氮占全氮比例的剖面分布均无明显规律。相同土层，水田和旱地土壤酸解各组分氮含量及其占全氮比例的规律性相同，即均为未知态氦〉氨态氮〉氨基酸态氮〉氨基糖态氮，而林地土壤酸解各组分氮含量及其占全氮比例则无明显规律。与水田相比，旱地和林地均可显著增加表层土壤酸解性全氮及酸解氨态氮、氨基酸态氮、氨基糖态氮的含量及其占全氮的比例，其中，旱地增加土壤酸解氨态氮的效果最为明显，而林地增加土壤酸解氨基酸态氮和氨基糖态氮的效果最为明显，总体上以水田改为林地后增加土壤易矿化分解的酸解氮的效果最为明显，提高土壤供氮的潜力最大。

英文摘要：

Contents of fractions of organic nitrogen（N） in the soil profiles of fields that had been under different land uses（paddy field,upland and forestland） for 16 years were determined with the Bremner method. Results show that nonacidolysable N was the dominant fraction of organic N in all the three soils （0 -60 cm in depth） , and the contents of acidolysable total N and acidolysable soil organic N fractions and their proportions to total N were,on the whole,the highest in surface soil（0 - 20 cm）. The content of acidolysable total N in 0 - 60 cm soil layer and contents of various acidolysable organic N fractions in 0 - 40 cm soil layer decreased with soil depth,but the proportions of acidolysable total N and various acidolysable organic N fractions to total N in 0 - 60 cm soil layer did not show any obvious regulations. Within the same soil depth,the paddy soil and the upland soil showed a similar regularity in contents of acidolysable total N and acidolysable soil organic N fractions and their proportions to total N,that is, unknown N 〉 ammonia N 〉 amino acid N 〉 amino sugar N,while the forest soil, did not show any obvious regularity in this aspect. Compared with paddy soil,upland soil and forest soil were more likely to increase the contents and their proportions to total N of acidolysable total N, acidolysable ammonia N,amino acid N and amino sugar N in the surface soil layer. In upland soil, the increase in acidolysable ammonia N was more significant,while in forest soil,the increase in acidolysable amino acid N and acidolysable amino sugar N was. As a whole,when paddy field was turned into forest land,the increase in eadily decomposable acidolysable N was the most significant,thus indicating that its potential of increasing soil N supply is the highest.