西双版纳不同演替阶段热带森林土壤N_2O排放的时间特征

Temporal Characteristics of Soil N_2O Emission of Different Succession Stages in Xishuangbanna Tropical Forests

氧化亚氮(N_2O)是导致全球变暖的一种重要温室气体。探明热带森林土壤N_2O排放动态及调控机制是全球变化及国际气候谈判的一个重要内容。为探明热带森林不同次生演替对土壤N_2O排放通量时间变化的影响,以西双版纳不同演替阶段热带森林[白背桐(Mallotus paniculatus)群落、崖豆藤(Mellettia leptobotrya)群落和高檐蒲桃(Syzygium oblatum)群落]为研究对象,采用静态箱-气相色谱法对土壤N_2O排放通量动态进行定位观测。探究这些变化与土壤温度和水分及理化性质之间的相互关系。结果表明:(1)不同次生演替阶段热带森林土壤N_2O排放通量存在显著差异,其大小顺序为:高檐蒲桃群落(462.4μg·m^(-2)·h^(-1))>崖豆藤群落(378.93μg·m^(-2)·h^(-1))>白背桐群落(310.68μg·m^(-2)·h^(-1));(2)不同次生演替阶段热带森林土壤N_2O排放通量月份变化趋势基本一致,均表现为6月显著高于12月,且各月份间差异显著;(3)土壤易氧化有机碳、水解氮、硝态氮和铵态氮显著影响土壤N_2O排放通量的时间变化,而土壤容重和pH值与土壤N_2O排放通量呈显著负相关。因此,土壤N_2O排放对西双版纳不同演替阶段热带森林群落具有敏感的响应,土壤温度、水分、易氧化有机碳、水解氮、硝态氮及铵态氮是土壤N_2O排放时间变化的主控因素。

Nitrous oxide(N2O)is an important greenhouse gas that causes global warming.Expounding the dynamics of N2O emissions from soil tropical forests and its regulatory mechanism is an important part of global change and international climate negotiations.This study aimed to understand the response of temporal dynamics of soil N2O to secondary succession in the tropical forests.The static chamber-gas chromatograph method was applied to explore the relationship of soil N2O emissions and soil temperature,moisture,and soil physiochemical properties in three secondary succession stages(i.e.,Mallotus paniculatus community,Mellettia leptobotrya community,Syzygium oblatum community)of Xishuangbanna tropical forests.The results were:(1)Soil N2O emissions varied significantly in three succession stages(P<0.05).The order was ranked as S.oblatum community(462.4μg·m^-2·h^-1)>M.acuminatan community(378.93μg·m^-2·h^-1)>M.paniculatus community(310.68μg·m^-2·h^-1).(2)The N2O flux had similarity in monthly variation in three succession stages,with the highest values observed in June,and lower ones in December.And(3)the temporal variation in soil N2O was positively affected by soil easily oxidized organic carbon,hydrolyzable nitrogen,NO3--N and NH4+-N.Whereas,the dynamics of soil N2O emissions were negatively correlated with soil bulk density and pH value.We can conclude that soil N2O emissions can sensitively response to the community succession in Xishuangbanna tropical forests.The variation in soil N2O emissions is attributed to the changes of the soil factors(e.g.,temperature,moisture,easily oxidized carbon,hydrolyzable nitrogen,and nitrate and ammonium nitrogen)in different succession stages of Xishuangbanna tropical forests.