Study On Soil CH₄?CO₂ Flux Of Chinese Fir Plantation In Different Ages

The increase of atmospheric greenhouse gas concentration is the main cause of global warming,among which CO2 and CH4 are the main contributors to the greenhouse effect,with a total contribution rate of over 80%.Compared with other ecosystems such as farmland,forest systems are an important part of the impact of global greenhouse gas emissions.Among them,forest land can reduce soil CO2 emissions and increase soil's ability to absorb CH4.Therefore,the characteristics of greenhouse gas(CO2,CH4)fluxes in forest soils were studied for the characteristics of Chinese fir forest in the central and southern regions,so as to obtain the source characteristics of greenhouse gas fluxes in plantation forest ecosystems.Control measures have great significance.In this paper,the Chinese fir forests of different ages in subtropical hilly areas were studied,and the changes of soil CH4 and CO2 fluxes and their influencing factors were studied.On this basis,the total amount of greenhouse gas emissions was also studied,and the global warming potential(GWP)evaluation analysis was carried out,and the following main conclusions were obtained:The soil CH4 flux of Chinese fir forest is the sink of atmospheric methane.The soil CH4 absorption flux is the highest in autumn,the lowest in winter,and the similar in spring and summer.The change of CH4 flux in different forest age was influenced by the season,of which the CH4 flux of the old forest(83a)changed the most.The change of CH4 flux in Chinese fir forest soil decreased first and then increased with the growth of forest age.The soil surface temperature had significant effects on the CH4 flux of the soils of other ages of Chinese fir except the young forest(3a),which had a significant effect on the soil CH4 flux in the old forest(83a).When the surface soil temperature was between 10-20?,the soil CH4 absorption flux of different forest ages reached the maximum.Both high temperature and low temperature will reduce the soil's absorption of CH4 flux.The temperature of soil 5cm underground had significant effects on the CH4 fluxes of different ages of Chinese fir forest soil.When the temperature is less than 15?,the soil CH4 uptake of different ages of Chinese fir forest increased with the increase of temperature.When the temperature was higher than 20?,the soil CH4 uptake of different ages of Chinese fir forest decreased with the increase of temperature.When the temperature is lower than 5?,the CH4 flux of some soils showed the discharge flux,and the soil performance of the old forest(83a)Chinese fir forest was the most obvious.Soil surface temperature and soil 5cm underground temperature have significant and above effects on soil CO2 flux in different forest ages.The CO2 fluxes in the soils of Chinese fir forests with different ages were all discharged.With the increase of temperature,the CO2 emission flux of the soils of Chinese fir forests increased.The effects of surface temperature on soil CO2 emission fluxes of different ages of Chinese fir forest land were ranked from large to small,followed by old forest(83a)>near mature forest(21a)>middle age forest(lla)>young forest(3a)>mature forest(32a).The sensitivity of soil CO2 emission fluxes to temperature of soil 5 cm underground in different ages was from strong to weak,followed by near mature forest(21a)>old forest(83a)>middle age forest(11a)>mature forest(32a)>young forest(3 a).The soil CO2 flux of Chinese fir plantation is the source of atmospheric carbon dioxide.The soil CO2 flux in summer fir forest land is the highest,and the CO2 flux is the lowest in winter.The soil CO2 fluxes in different forest ages increased with the increase of forest age and generally increased and then decreased.The CH4 absorption effect is best in mature forest(32a)and old forest(83a).The net emission flux of CH4 generally showed a trend of decreasing first and then rising.The annual CO2 emission flux of different Chinese fir forests is basically rising before the near mature forest(21a).After near-maturing forests(21a),the annual emissions are basically declining.Before the mature forest of Chinese fir(21a),the global warming potential(GWP)of Chinese fir forest increased.After the mature forest of Chinese fir forest(32a),the global warming potential(GWP)of Chinese fir forest soil decreased.