不同CO_(2)浓度和施氮水平对麦田CO_(2)净通量的影响

Effect of different elevated CO_(2) concentrations and nitrogen application on net CO_(2) fluxes in wheat field

为研究不同CO_(2)浓度和施氮量对麦田CO_(2)净通量的影响,利用开顶式气室(OTC)组成的CO_(2)浓度自动调控平台模拟CO_(2)浓度升高环境.以冬小麦为试验材料,设置CK(对照,环境大气CO_(2)浓度)、C_(1)(CO_(2)浓度比CK增加120μmol·mol^(-1))和C_(2)(CO_(2)浓度比CK增加200μmol·mol^(-1))3个CO_(2)浓度水平;施氮量设置常规施氮量(N_(1),25 g·m^(-2))和低氮(N_(2),15 g·m^(-2))2个水平.采用静态箱-高精度气体分析仪观测麦田CO_(2)净通量.结果表明:各处理的麦田CO_(2)净通量变化特征一致,均呈先增大后减小的趋势,在拔节期和抽穗期达到峰值.N_(1)处理下,在整个生育期,CK、C_(1)和C_(2)处理的CO_(2)累积量分别为-105.8±12.6、-123.1±11.5和-120.2±4.1 kg·hm^(-2).N_(2)处理下,在整个生育期,CK、C_(1)和C_(2)处理的CO_(2)累积量分别为-82.3±9.2、-95.4±7.6和-96.7±2.8 kg·hm^(-2);拔节期C_(2)处理的CO_(2)累积量比CK显著增加了31.8%(P=0.024).C_(1)处理下,拔节期N_(1)处理的CO_(2)累积量显著高于N_(2)处理55.0%(P=0.009);C_(2)处理下,N_(1)处理的整个生育期CO_(2)累积量显著高于N_(2)处理23.6%(P=0.010).各处理CO_(2)净通量跟土壤湿度的相关关系均达到显著;N_(1)处理下,C_(1)和C_(2)处理的CO_(2)净通量跟光合有效辐射的相关关系达到显著,N_(2)处理下,CK和C_(1)处理的CO_(2)净通量跟光合有效辐射的相关关系达到显著;N_(1)处理下,C_(1)处理的CO_(2)净通量跟空气温度的相关关系达到显著,其余处理未达到显著.本研究表明:在小麦的拔节期和抽穗期,相比于CO_(2)浓度升高,施氮量对麦田CO_(2)净通量的影响更为显著;CO_(2)浓度升高与施氮量对麦田CO_(2)净通量的影响没有显著的交互作用.

To investigate the effect of different CO_(2) concentrations and nitrogen application on net CO_(2) fluxes in wheat field,an automatic CO_(2) concentration control platform consisting of open-top chamber(OTC)was used to simulate an elevated CO_(2) concentration environment.Three CO_(2) concentration levels were set:CK(ambient atmospheric CO_(2) concentration),C_(1)(CO_(2) concentration increased by 120μmol·mol^(-1) compared with CK)and C_(2)(CO_(2) concentration increased by 200μmol·mol^(-1) compared with CK);two nitrogen fertilizer treatments were set at regular nitrogen fertilizer(N_(1),25 g·m^(-2))and low nitrogen fertilizer(N_(2),15 g·m^(-2)).The net CO_(2) fluxes in the wheat field were observed using a static chamber-high precision gas analyzer.The results showed a consistent trend of net CO_(2) fluxes in wheat field under all treatments:increased until peaked at the jointing and heading stages,and then decreased.Under the N_(1) treatment,the CO_(2) accumulation under CK,C_(1) and C_(2) treatments were-105.8±12.6,-123.1±11.5 and^(-1)20.2±4.1 kg·hm^(-2),respectively.Under the N_(2) treatment,the CO_(2) accumulation under CK,C_(1) and C_(2) treatments were-82.3±9.2,-95.4±7.6 and-96.7±2.8 kg·hm^(-2),respectively;the CO_(2) accumulation of C_(2) treatment at jointing stage was significantly higher than that of CK by 31.8%(P=0.024).Under the C_(1) treatment,the CO_(2) accumulation of N_(1) treatment was significantly higher than that of N_(2) treatment by 55.0%(P=0.009)at the jointing stage.Under the C_(2) treatment,the CO_(2) accumulation of N_(1) treatment was significantly higher than that of N_(2) treatment by 23.6%(P=0.010)during the whole growth stage.The correlation between net CO_(2) fluxes and soil moisture reached significance under all treatments.Under the N_(1) treatment,the correlation between net CO_(2) fluxes and photosynthetic effective radiation under C_(1) and C_(2) treatments was significant,and under the N_(2) treatment,the correlation between net CO_(2) fluxes and photosynthetic effective radiation under CK and C_(1) treatment was significant.Under the N_(1) treatment,the correlation between net CO_(2) fluxes and air temperature was significant only under C_(1) treatment.This study showed that the effect of nitrogen application on the net CO_(2) fluxes in wheat field was more significant than that of elevated CO_(2) concentration at the jointing and heading stages of wheat,and there was no significant interaction between the elevated CO_(2) concentration and nitrogen application on the net CO_(2) fluxes in wheat field.