大气CO_(2)浓度缓增对冬小麦土壤呼吸的影响

Effects of gradual increase of atmospheric CO_(2) concentration on soil respiration of winter wheat field

为研究大气CO_(2)浓度缓增对冬小麦(Triticum aestivum)土壤呼吸的影响,基于开顶式气室组成的CO_(2)浓度自动调控平台,在2017—2019年开展了两季冬小麦CO_(2)浓度缓增试验.每季试验在背景大气CO_(2)浓度基础上(CK,对照),均设置了CO_(2)浓度缓增处理(C_(80)和C_(120),即从2016年起逐年增加40μmol·mol^(-1),至2017—2018年和2018—2019年冬小麦生长季CO_(2)浓度分别为CK+80μmol·mol^(-1)和CK+120μmol·mol^(-1)).采用静态暗箱-气相色谱法测定土壤呼吸速率.结果表明:CO_(2)浓度缓增没有显著改变土壤呼吸的季节变化规律,但是会显著影响冬小麦旺盛生长期的土壤呼吸速率.在2018—2019年冬小麦抽穗-扬花期,C_(120)处理使土壤呼吸速率显著增加50.2%(P=0.008),且使得生长季土壤碳排放显著增加25.9%(P=0.044),而在2017—2018年冬小麦生长季,与CK相比,C_(80)处理对土壤呼吸没有显著影响.土壤呼吸与土壤温度呈指数正相关,与CK相比,CO_(2)浓度缓增降低了土壤呼吸对温度的敏感性.研究表明,CO_(2)浓度缓增120μmol·mol^(-1)增加了冬小麦生长季土壤碳排放.

To examine the effects of gradual increase of atmospheric CO_(2) concentration on soil respiration of winter wheat(Triticum aestivum)field,a gradually increased CO_(2) concentration experiment was conducted with automatic control system of CO_(2) in open top chambers(OTCs)during 2017-2019 growing seasons.In this study,a gradual increase of atmospheric CO_(2) concentration(C_(80) and C_(120),an increase of 40μmol·mol^(-1) year by year from 2016)was set up based on the ambient atmospheric CO_(2) concentration(CK).The soil respiration rate(R_(s))was measured by static chamber-gas chromatograph method.The results showed that gradually increased CO_(2) did not alter the seasonal patterns of soil respiration,but had significant effect on R_(s) during winter wheat bloom-growth period.In 2018-2019 growing season,compared to CK,C_(120) treatment significantly increased R_(s) by 50.2%(P=0.008)at the heading-flowering stage,and significantly increased cumulative amount of CO_(2) emissions(CAC)by 25.9%(P=0.044)during the wheat growing season;while in 2017-2018 growing season,compared to CK,C 80 treatment had no significant effect on R s.A positive exponential relationship was found between soil respiration rate and soil temperature.Compared to CK,gradually increased CO_(2) concentration reduced the temperature sensitivity coefficient of soil respiration(Q_(10) values).In summary,a gradual increase of atmospheric CO_(2) concentration of 120μmol·mol^(-1) increased CAC during the growing season of winter wheat.