神农架大九湖泥炭湿地CO_2通量特征及其影响因子

Characteristics of CO_2 Flux and Their Effect Factors in Dajiuhu Peat Wetland of Shennongjia

泥炭地在全球碳循环中起着重要作用,其碳源、碳汇功能的转变已成为研究全球气候变化的热点。为研究湖北省神农架林区大九湖亚高山泥炭湿地碳排放特征及影响因素,采用涡度相关法对大九湖泥炭湿地CO_2通量进行了观测,选取2016年6—8月作为生长季和2015年12月—2016年2月作为非生长季,对比分析泥炭湿地在不同生长季节CO_2通量的变化规律及其影响因子。结果表明,(1)大九湖泥炭湿地生态系统生长季CO_2通量的日变化规律明显,整体呈"U"型曲线,日变化范围为-6.84~6.65μmol·m^(-2)·s^(-1);非生长季CO_2通量变化趋势平缓,在-0.88~5.19μmol·m^(-2)·s^(-1)之间。(2)白天生长季与非生长季的CO2通量与光量子通量密度(PPFD)均符合直角双曲线关系,但生长季PPFD与CO_2通量的拟合效果(R^2=0.427 3,P<0.01)优于非生长季(R^2=0.045 6,P<0.01)。(3)生长季的气温(Ta)与CO_2通量呈二次曲线相关(R^2=0.248 6,P<0.01),CO_2通量随Ta的升高呈先增加后降低;非生长季Ta与CO_2通量(R^2=0.042 8,P<0.01)相关性显著,两者呈负相关,但Ta仅能解释CO_2通量4.28%的变异数据。(4)土壤温度(Ts)和土壤含水量(SWC)对CO_2通量的影响,主要体现在生态系统呼吸上。生长季夜间生态系统呼吸受Ts与SWC的共同影响(R^2=0.199 5,P<0.01),生态系统呼吸的温度敏感性Q10值为1.84;非生长季夜间生态系统呼吸与Ts、SWC的相关性均不显著(P>0.05)。

Peatland ecosystems play an important role in global carbon cycle.Peatlands may act as carbon source or carbon sink.This function transformation of carbon has become one of the topic issues of studies on global climate change.In order to study the characteristics of carbon flux and factors influencing carbon flux in Dajiuhu wetland(in Shennongjia Forestry Administrative District,Hubei province,China),we monitored C〇2flux and environmental factors such as photosynthetic photon flux density(PPFD),air temperature(Ta),soil temperature(Ts)and soil water content(SWC)in a field station in Dajiuhu,and investigated variation patterns of C〇2flux and analyze which environmental factors can affect C〇2flux during the growing season(from June to August of2016)and non-growing season(December2015to February2016).The results showed that:(1)The average diurnal variation of C〇2flux in growing season demonstrated a U-type curve,range from-6.84to6.65^molm"2^"1.In non-growing season,diurnal C〇2flux ranging from-0.88to5.19^molm"2^"1.(2)The relationship between the daytime C〇2flux and photosynthetic photon flux density(PPFD)could be fitted by rectangular hyperbola models in the both growing and non-growing season.However,the fitted curve in the growing season(^2=0.4273,P<0.01)had a better goodness of fitting than that of the non-growing season(R2=0.0456,P<0.01).(3)In the growing season,relationship between C〇2flux and air temperature(Ta)could be described as an aquadratic curve(R2=0.2486,P<0.01),and the C〇2flux first increased and then decreased when Ta increasing.The correlation between C〇2flux and air temperature in non-growing season was significantly negative(R2=0.0428,P<0.01),and the relationship is negative,but only4.28%of the C〇2flux variation could be explained by air temperature.(4)The influence of soil temperature(Ts)and soil water content(SWC)on C〇2flux was mainly reflected in ecosystem respiration.SWC and Ts were the main factors that influenced nighttime ecosystem respiration in growing season,and the temperature sensitivity of the ecosystem respiration Qiq was1.84.Nevertheless,in the non-growing season,the correlation between the nighttime ecosystem respiration and Ts(or SWC)was not significant(P>0.05).