Diurnal change of soil carbon flux of island forests:A case study in Beichangshan Island

By employing the LI-8100 CO2 flux automatic monitoring system (LI-COR Inc.,Lincoln,NE,USA),this paper measured the diurnal changes of the soil carbon flux in the artificial plantations on the Beichangshan Island of Shandong Province.The diurnal changes of soil carbon flux and its environmental factors such as temperature and water were analyzed.The results indicated that soil carbon flux appeared single diurnal pattern,with the peaks presented at about 14:30 and the lowest presented at about 06:00.The diurnal average of soil carbon flux ranged from 1.835 mol/(m2s) to 14.475 mol/(m2s).Significant relationships were found between soil respiration rate and soil temperature (10 cm),which could be best described by exponential equations (R2=0.492-0.702, P0.05).The Q10 value was based on the exponential correlations,which represented the sensitivity of soil respiration to temperature. Its values of Robinia pseudoacacia in May, Pinus thunbergii in May, Robinia pseudoacacia in Aug, Pinus thunbergii in Aug were 1.448,1.301,3.254,3.445,respectively.There were exponential correlations (R2=0.689,P0.05),quadratic correlations (R2=0.819,P0.05) and linear correlations(R2=0.363-0.601,P0.05)between respiration rate and soil moisture (0~10 cm).Owing to the soil moisture condition,the soil moisture in May had more influence on soil carbon flux than that in August.On the whole,the important regulative factors to soil carbon flux were soil temperature (10 cm)and soil moisture (0~10 cm),and its combined effect could account for more than 73.1% of the soil carbon flux changes on the Beichangshan Island(R2=0.73-0.91,P0.05).