氮添加对沙质草地微生物呼吸与根系呼吸的影响

Effects of nitrogen addition on microbial respiration and root respiration in a sandy grassland

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CO_2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Q_(10)值,也提高了二者对土壤水分变化的敏感程度.

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）. Mi- crobial 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.