垦殖对伊犁河谷湿地土壤可溶性有机氮含量的影响

Effects of reclamation on soil soluble organic nitrogen contents in wetlands of the Ili River Valley

【目的】研究垦殖对伊犁河谷湿地土壤可溶性有机氮(SON)的影响,为该区湿地的开发保护和氮素调控提供科学依据。【方法】以伊犁河谷的芦苇湿地及其垦殖而成的稻田为研究对象,分层采集0~100 cm的土壤样品,分析垦殖对垂直方向上土壤SON含量的影响,并探求SON与土壤理化性质和其他氮组分之间的关系。【结果】在0~100 cm土壤深度内,芦苇湿地和稻田土壤的SON含量占土壤可溶性总氮(TSN)含量的58.9%~74.1%,表明SON是该区域土壤可溶性氮素的主要组成部分;土壤SON含量在垦殖后降低了16.7%~40.5%,在≥20~60cm土层表现为显著降低,表明垦殖对土壤可溶性有机氮的影响不仅限于表层土壤,这缘于湿地和稻田土壤的高含水率使得土壤SON在垂直方向上的移动性较强;湿地土壤的有机碳和全氮在垦殖后大幅减少,其中垦殖前的含量分别是垦殖后的2.9~5.9倍和2.0~6.0倍。总体上讲,土壤碳氮比、微生物量氮、铵态氮和硝态氮在开垦前后的变化不大,只有0~20 cm土层的微生物量氮和硝态氮在垦殖后显著降低(P<0.05);土壤SON与土壤有机碳和全氮表现出显著的相关性,说明垦殖后土壤有机质水平的降低是SON含量下降的主要原因。【结论】土壤SON是伊犁河谷湿地土壤可溶性氮素的主要形态,但其含量在湿地垦殖为稻田后表现出减少的趋势。

[ Objective] To investigate the effect of reclamation on soil soluble organic nitrogen （SON） contents in wetland of the Ili River Valley, which could provide basis for the exploitation, protection and nitrogen regulation of wetlands in this area. [ Method] Soil samples of 0-100 cm were collected at different depths from a reed （Phragmites australis （Cav.） Trin. ex Steud. ） wetland and a paddy field which converted from this wetland to study the effect of reclamation on profile distribution of soil SON content, and to analyze the relationships between soil SON and physicochemical prop- erties/other nitrogen fractions. [ Result ] Soil SON contents of reed wetland and paddy field accounted for 58.9%-74.1% of soil total soluble nitrogen （TSN） contents in the 0-100 cm soil layers, indicating that SON was the main component of soil soluble nitrogen in the study area. Soil SON contents decreased by 16.7%-40.5% after reclamations and the decreases were significant in the ≥20-60 cm soil layers. These results indicated that the effect of reclamation on soil SON content was not limited to topsoil, possibly due to that the high soil water contents of wetland and paddy field promoted the mobility of soil SON. Soil organic carbon content and total nitrogen content decreased considerably after reclamation, and the contents before reclamation were 2.9-5.9 times and 2.0-6.0 times higher than those after reclamation, respec tively. In general, the ratio of carbon to nitrogen, microbial biomass nitrogen, ammonium nitrogen and nitrate nitrogen showed little response to the reclamation, only the contents of microbial biomass nitrogen and nitrate nitrogen in the 0-20 cm soil layer was significantly （P〈0.05） decreased by reclamation. The significant （P〈0.01） correlations between soil SON and organic carbon/total nitrogen suggested that the decreas of soil organic matter content after reclamation was the main reason for the decreased soil SON contents. [ Conclusion] Soil SON is the major part of soil soluble nitrogen in the Ill River Valley, but its content showed a decreasing tendency after reclaiming into paddy field.