冻融交替对高寒草甸N_2O排放速率的影响

Effect of alternative freezing and thawing on nitrous oxide rates in alpine meadow

采用室内培养方法,分析了高寒矮嵩草草甸土壤N_2O排放速率对土壤冻融交替作用的响应特征。结果表明:随着冻结时间增加,-10℃和-5℃冻结土壤N_2O排放速率均明显降低,且前者的降低速率显著高于后者、均低于对照土壤N_2O排放速率;随着冻结土壤的融化,-10℃和-5℃培养土壤N_2O排放速率急剧增加,融化2h出现排放峰值,而后逐渐降低,但均高于对照样地,在冻结21d时,各处理高寒草甸土壤N_2O排放速率达到最低值。随着冻融交替循环次数从1次增加到12次,高寒草甸土壤N_2O排放速率明显增加,从最初的1.23±0.05g/(kg·h)增加到3.34±0.59g/(kg·h)。从第12次到第24次冻融循环时,高寒草甸土壤N_2O排放速率显著下降(P<0.05),降低幅度达到31.7%。土壤冻融过程会显著激发高寒草甸N_2O排放速率,有助于科学估算高寒草甸N_2O排放量。

Alpine meadow was dominated on the Tibetan Plateau.It was revealed as a source of atmosphere N_2O.Seasonal alternatively freezing and thawing process was one of the main climate characteristic on the Tibetan Plateau.The response of N_2O emission flux of alpine Kobresia meadow to alternatively freezing and thawing was studied by laboratory incubation.The result indicated that soil N_2O emission rates decreased gradually under-10℃ and-5℃incubation condition along with the increasing of freezing time.The rate of dropping in the former was significantly higher than the latter,and both fluxes were lower than the control.Along with the increasing of temperature,soil N_2O emission rates increased dramatically under-10 and-5℃incubation,and the fluxes reached at the peak in 2 hours,and then the rates decreased gradually.Meanwhile,the lowest emission rates of all plots were measured after freezing 21 days.In addition,alpine meadow ecosystem N2O emission rates increased significantly from 1.23±0.05 to 3.34±0.59 g/（kg·h）with the increase of freezing and thawing process from 1 to 12.After that the flux decreased dramatically till 24 cycles.Processes of the alternative freezing and thawing could significantly stimulate the emission rates of N2O.This study would contribute to accurate estimation of N2O emission quantity in alpine meadow.