Soil respiration includes root respiration and microbial respiration. Effects of nitrogen addition on root respiration and microbial respiration may be quite different. We examined the effects of N-addition on the releasing of soil CO2 and the responses of root respiration and microbial respiration in a Keerqin sandy grassland, Northeast China. Results showed that both soil respiration and microbial respiration firstly rose then declined during the growing season (May to October). Microbial respiration was the main contributor of soil respiration, accounting for 82.6%. Contribution rate of root respiration altered with months, peaking in May (49.4%) and August (41.9%), with an average contribution rate of 17.4% during the growing season. Root respiration (with a decrease of 17.7%) was more sensitive to N-addition compared with microbial respiration (with a decrease of 3.9%) at 10 ℃. N-addition increased Q10 values of soil respiration and microbial respiration, and enhanced their sensitivity to soil water content variation.
土壤呼吸可以细化为根系呼吸和微生物呼吸,二者对氮添加的响应有所不同.本文以科尔沁沙质草地为研究对象,探讨氮添加对土壤CO2排放的影响,并细化为微生物呼吸和根系呼吸的响应特征.结果表明: 在观测期(5—10月),土壤呼吸、微生物呼吸月动态均呈先升高后降低的趋势;微生物呼吸是土壤呼吸的主要贡献者,占82.6%;观测期内根系呼吸贡献率随月份而变化,根系呼吸贡献率两个峰值分别出现在5月(占49.4%)和8月(占41.9%),6个月的平均贡献率为17.4%;在10 ℃条件下,根系呼吸较微生物呼吸对氮添加的响应更为敏感,微生物呼吸速率在氮添加后降低了3.9%,而根系呼吸降低了17.7%;氮添加提高了土壤呼吸、微生物呼吸温度敏感性Q10值,也提高了二者对土壤水分变化的敏感程度.
Keywords: Keerqin sandy land; Q 10; R 10; nitrogen fertilizer; soil respiration.