| Methane(CH4)is the second most important anthropogenic greenhouse gas in the atmosphere.Atmospheric CH4 had raise since the industrial revolution,and reached a new high of 1833 ppb in 2014.This value constitute 254%of its pre-industrial levels.It was estimated that subtropical and tropical forest soils contribute 28%to global CH4 uptake,which was an important sink of atmospheric CH4.The eleven soil samples in this study were collected from nine litchi orchards and Haikou Volcano Park in Hainan Island,China.The present study aimed at determining effects of temperature,soil moisture,and exogenous nitrogen in soils of different types through laboratory incubation.And it was meaningful to take measures to enhance the soil sink of CH4.The major findings are as follows:(1)Humi-Udic Andosols(H1);Haplic-Udic Andosols(H2);Udic-Vitric Andosols(H3);Rhodi-Udic Ferralosols(T1,T2);Hapli-Udic Ferralosols(T3);Acidi-Udic Argosols(L1);Argi-Udic Ferrosols(F1);Hapli-Udic Ferrosols(F2);Ali-Udic Cambosols(Cl)and one litchi soil which type was unknown(B1)could oxidize CH4.Andosols showed the highest oxidizing CH4 abilities range from 87.56-105.58 ng·kg-1·h-1 while others were all in the range of 40.34-68.66 ng·kg-1·h-1.(2)Correlation analysis showed that organic matter content had significant effects(p<0.05)on the CH4 oxidation rates of nine litchi orchard soils,while the total phosphorus had higher significant level(p<0.01).(3)Temperature could significantly affect CH4 oxidation rates of eleven soils in this study(p<0.05).Rhodi-Udic Ferralosols(T1,T2);Hapli-Udic Ferralosols(T3);Acidi-Udic Argosols(L1);Argi-Udic Ferrosols(F1);Hapli-Udic Ferrosols(F2);Ali-Udic Cambosols(C1)and one litchi soil which type was unknown(B1)had the maximun CH4 oxidation rates when cultivated at 30℃ while the optimum temperature of three kinds of Andosols were not found in this study.Soil moisture could also significantly affect CH4 oxidation rates(p<0.05).The CH4 oxidation rates of all kinds of soils increased with increasing soil moisture before reaching the optimum soil moisture and decreased with decreasing soil moisture after reached the optimum soil moisture.The optimum soil moisture for soil CH4 consumption of Andosols was 17%～19%,while litchi orchard soils was 16%～21%.(4)Addition of KNO3 at 100 mg N kg-1 d.w.s.did not result in significant inhibition of CH4 oxidation in Humi-Udic Andosols(H1);Haplic-Udic Andosols(H2)and Udic-Vitric Andosols(H3).and the CH4 oxidation rates reduced by 9.23%,8.96%,10.11%respectively.There were significant difference between the same addition of KNO3 and(NH4)2SO4.at 100 mg N kg-1 d.w.s.(p<0.05).The CH4 oxidation rates of Humi-Udic Andosols(H1);Haplic-Udic Andosols(H2)and Udic-Vitric Andosols(H3)reduced by 32.46%,37.63%,35.86%respectively after adding(NH4)2SO4 at 100 mg N kg-1 d.w.s.As for nine litchi orchard soils,addition of KNO3 at 100 mg N kg-1 d.w.s.only result in significant inhibition of CH4 oxidation in Hapli-Udic Ferralosols(T3);one litchi soil which type was unknown(B1)and two kinds of Rhodi-Udic Ferralosols(T1,T2),and their CH4 oxidation rates reduced by 32.42%,20.87%,29.95%,22.20%respectively.The CH4 oxidation rates of Udic-Vitric Andosols(H3)and Acidi-Udic Argosols(L1)had significant difference between the same addition of KNO3 and(NH4)2SO4,at 100 mg N kg-1 d.w.s.(p<0.05).For all assayed litchi orchard soils,percent inhibition by ammonia increased with increasing concentration of added ammonia,which trend was fit well by linear regression. |
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