水分对尕海湿地退化演替土壤氮矿化的影响

Effect of water on nitrogen mineralization in degraded succession of GahaiWetland

水分是湿地土壤氮矿化过程的主要调控因子,对于湿地土壤中氮素循环过程具有重要作用。以甘南尕海湿地为研究对象,设置4个退化程度(未退化UD、轻度退化LD、中度退化MD和重度退化HD)和4个田间持水量(20%FC、40%FC、60%FC和80%FC),通过室内49 d的好气培养,测定各处理条件下湿地土壤在0~10 cm土层的土壤氮矿化特征。结果表明:(1)在各水分条件下,随着培养时间的延长,4种退化程度土壤氨化速率、硝化速率和净氮矿化速率均呈先增大后减小的趋势。(2)土壤净氮矿化量均值随水分的增加先增大后减小,60%FC条件下,各退化程度土壤净氮矿化量均值变化范围为34.91~44.94 mg·kg^(-1),较20%FC、40%FC和80%FC分别高出22.31~30.29mg·kg^(-1)、10.91~19.84 mg·kg^(-1)、8.57~19.50 mg·kg^(-1)。(3)土壤净氮矿化量均值和净氮矿化速率均值均随湿地退化程度的增加而减小。适宜水分有利于土壤氮矿化,而水分过高不利于土壤氮矿化;同时,湿地退化降低了土壤氮矿化。

Moisture is the main regulatory factor of nitrogen mineralization processes in wetland soils,where it also plays an important role in nitrogen circulation.Using Gannan Gahai wetland as study area,four degradation gradients(nondegraded,UD;slightly degraded,LD;moderately degraded,MD;and severely degraded,HD),and four field water holding capacity(20%FC,40%FC,60%FC and 80%FC)-were established,and the nitrogen mineralization characteristics of the wetland soil in the 0-10 cm soil layer were measured by aerobic incubation for 49 days.The results showed that(1)under various water conditions,the ammoniation,nitrification,and net nitrogen mineralization rates increased at first,and then decreased with the increase of incubation time.(2)With the increase in water content,the average value of soil net nitrogen mineralization initially increased and then it decreased;at 60%FC,the value in degraded soil was 34.91-44.94 mg·kg^(-1),compared with 20%FC,40%FC,and 80%FC,it was 22.31-30.29 mg·kg^(-1)、10.91-19.84 mg·kg^(-1)、8.57-19.50 mg·kg^(-1),respectively.(3)The mean value of net nitrogen mineralization and its corresponding rate decreased with the increasing level of wetland degradation.An adequate amount of moisture favors soil nitrogen mineralization,while excessive moisture is unfavorable to this process and,at the same time,wetland degradation reduces it.