Abstract: In order to figure out the effects of surface cover on soil organic nitrogen composition, this paper selected four soil samples with different surface vegetations in Qixingguan district, Bijie city, Guizhou, including dry-farmland (YJ), woodland (LT), grassland (YH), and abondoned-land (CJ). Their indexes of total nitrogen (TN) and acidolysable total N (ATN) composition were detected and analyzed. The results showed that: ① Two factor analysis of variance indicated that vegetation cover had a significant effect on the contents of soil TN and non-acidolysable N (NAN). However, soil depth had a non-significant effect on ATN. The order of TN values was YJ (1.421 g·kg-1)>LT (1.274 g·kg-1)>YH (0.972 g·kg-1)>CJ (0.859 g·kg-1). ② There was a significant correlation between soil TN and NAN in four sample sits, which was related to the lack of accumulated temperature in the study area, leading to the slow humification process, and the original nitrogen-containing substances such as carbohydrates constituting the main components of NAN. Even though the TA distribution of YH was abnormal, the ATN still decreased with the deepening of soil levels, which suggested that the vertical distribution had certain commonness, and there was limited effect by the environment factors such as surface cover. ③ The order of ATN composition was amino acid N (0.322 g·kg-1)> ammonia N (0.214 g·kg-1) >unknown N (0.180 g·kg-1) > amino sugar N (0.117 g·kg-1). Variance analysis sugested that the effect of surface cover on ammonia N was significant; however, the effect of soil depth on all ATN composition was not significant. ④ The mean of amino sugar N in YJ sample site was 0.026 g·kg-1, which was related to the toxic effect of pesticide application on microorganisms, thus reducing the biological supply of sugar nitrogen. The present research revealed the influence of environmental conditions such as surface cover on soil organic nitrogen components, which could provide theoretical reference for improving soil nitrogen study in Northwest Guizhou.

Key words: soil surface cover, soil profile, total nitrogen, organic nitrogen, northwestern district of Guizhou

摘要： 为研究地表覆被对土壤有机氮组分的影响，选择贵州省毕节市七星关区覆被差异明显的旱耕地(YJ)、林灌地(LT)、灌草地(YH)和撂荒地(CJ) 4种样地类型，检测不同覆被等环境条件对土壤全氮和有机氮组分等的影响。结果表明：①双因素方差分析显示，地表覆被对土壤全氮和非酸解氮有显著影响，而土层深度对酸解总氮有影响，但并未达到显著水平。样地土壤剖面全氮的大小排序为YJ (1.421 g·kg-1)>LT (1.274 g·kg-1)>YH (0.972 g·kg-1)>CJ (0.859 g·kg-1)。②各样地土壤全氮含量与非酸解氮含量相关性达显著水平，这与研究区积温不足导致腐殖质化过程缓慢，碳水化合物等原始形态的含氮物质构成非酸解氮的主要成分有关。即使YH剖面全氮分布有异常，但其酸解总氮也随深度加深而下降，这表明其垂直分布具有一定的共性，且受地表覆被等因素影响有限。③酸解各形态氮的大小关系依次为酸解氨基酸态氮(0.322 g·kg-1)>酸解氨态氮(0.214 g·kg-1)>酸解未知态氮 (0.180 g·kg-1)>酸解氨基糖态氮(0.117 g·kg-1)。方差分析显示，土壤酸解氨态氮受地表覆被的影响达到显著水平，而酸解各形态氮受土层深度影响均不显著。④旱耕地酸解氨基糖态氮均值仅为0.026 g·kg-1，这与农药施用对微生物的毒害作用减少了糖态氮的生物补给有关。结果揭示了地表覆被等环境条件对土壤有机氮组分的影响，可为黔西北改善土壤氮素状况提供理论参考。

关键词: 地表覆被, 土壤剖面, 全氮, 有机氮, 黔西北