| In this paper,the 70-year-old mixed forest of deciduous broad-leaved mixed forests of Aphananthe aspera and Celtis sinensis and Pinus massoniana and Liquidambar formosana broad-leaved mixed forest in Zijin Mountain,Nanjing,was used as research objects to study the CH4 flux of two types of forest soils.Influenc ing factors of soil CH4 flux in two different types of forest,and through the Pearson correlation coefficient to find out the dominant factors of soil CH4 flux,in order to explain the reasons for the differences in soil CH4 flux variation in two different forest types.The reasons for the variation in soil CH4 fluxes had provided scientific advice for urban forest management and operation.The main results of research were as follows:?1?The CH4 fluxes of the soil in the two kinds of mixed forests showed the sink of atmospheric CH4,and the amount of CH4 absorbed per hectare of soil per year.The deciduous broad-leaved mixed forest was 1.12 kg/hm2,and the coniferous-broad-leaved mixed forest was 3.25 kg/hm2.The coniferous and broad-leaved mixed forest had higher absorption of CH4 than deciduous broad-leaved mixed forest.?2?The CH4 flux in the soils of two different forest types in Zijin Mountain of Nanjing showed a high CH4 flux during the non-growth season,and a high CH4 uptake flux during the growing season.The forest soils from November to March CH4 was emitted into the atmosphere as the source of CH4,and from April to October forest soil absorbed CH4 in the atmosphere,which was the sink of CH4.In April,the soil CH4source was converted into soil CH4 sink,and in November the soil CH4 sink was transformed into soil CH4 source again..?3?Soil temperature had a good correlation with soil CH4 flux,which was the main factor affecting soil CH4 flux.Soil temperature mainly affected the activity of soil microorganisms,and then affected CH4 flux.The average temperature of the two types of forest soil during the growing season was 22.70°C,which was located within the optimum temperature range of 20-30°C for methane oxidizing bacteria.?4?During the growing season of coniferous and broad-leaved mixed forests,the total carbon content was greater than that of deciduous broad-leaved mixed forests.The total carbon provided a carbon source for the soil microorganisms in the soil.The total carbon content increased the metabolism of methane microorganisms,thereby promoting the absorption of soil CH4.The absorption of CH4 flux in coniferous and broad-leaved mixed forest was greater than that in deciduous broad-leaved mixed forest.?5?In the soils of two different forest types,the decrease of total nitrogen content during the growth season was favorable to the absorption of soil CH4 in the two forest types.?6?Coenzyme F420 was not significantly correlated with the linear analysis of soil CH4 fluxes in two different forest types.The increase in coenzyme F42020 during the non-growth season not only did not promote the production of soil CH4,but increased the absorption flux of soil CH4.Related to the inactivation of coenzyme F420.However,the dehydrogenase fluctuated little during the entire observation period and had little relationship with soil CH4 flux.In summary,the soils of deciduous broad-leaved mixed forest and coniferous and broad-leaved mixed forest can be used as the absorption sink of CH4 in the two types of forests.Coniferous and broad-leaved mixed forests took longer and larger to absorb CH4 than deciduous and broad-leaved mixed forests.In order to increase the absorption of CH4 in soil,conifer forest species can be moderately increased in other types of forests during the subsequent forest management and management,and a more complete forest system system can be established. |
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