CH₄ Fluxes And Its Effect Factors For Four Forests In Nanling Area

Methane(CH4)is a potent greenhouse gas that is second only to carbon dioxide(CO2)in the global scale of greenhouse gases.It is important to study the relationship between forest soil and CH4 flux and its influence factors on greenhouse effect,and provide theoretical basis for further effective emission reduction.This study four kinds of typical forest types in the nanling area(mountain dwarf forest,evergreen broad-leaved forest,mixed coniferous and broad-leaved mixed forest needle)as the research object,using static chamber-gas chromatograph technique observation 4 types of forest soil CH4 flux,different types of forest soil CH4 flux dynamics,and to explore the influence factors of soil CH4 fluxes(soil temperature,moisture,soil nutrients,etc.).(1)The four types of forest type CH4 flux are generally expressed as a foreign exchange,and its order is in the order of evergreen broad-lavedforeys>broad-leaved forest>broad-leaved forest.The four types of forest showed a certain pattern of dynamic changes in the month.Four forest types of CH4 absorption ability general representation for:mixed forest>needle broadleaf mixed forest>mountain coppice>evergreen broad-leaved forest,the mixed needle for four forest types of forest types of CH4 absorption ability is strongest.The four types of forest show a certain seasonal pattern of changes,which are present in winter,and different absorption in spring,summer and autumn.Overall,spring winter two season compared with the average soil CH4 flux is higher,the autumn and summer low compared with the average soil CH4 flux,summer and autumn flux floating is bigger.In the spring and summer,the combination of the combination of the combination of the combination of the combination of the combination of the combination of the combination of the combination of the CH4 and the CH4 is strong,the autumn evergreen broadleaf forest CH4 absorbs better,and the winter mountain dwarf forest CH4 absorbs better.(2)CH4 flux in four types has a negative correlation with soil surface and temperature on 10-centimeter soil(P<0.01).Temperature in the soil between 5 and 10 centimeters has a high correlation with CH4 flux,and as temperature increases,sinks of CH4 in four forest types has remarkably strengthened.Annual soil temperatures in four forest types have no evident different and the annual soil temperatures decrease as the following sequence:deciduous broad-leaved mixed forest,broad-leaved evergreen forest,coniferous and broad-leaved mixed forest,mountain coppice.(3)Mountain coppice,ranking the first in moisture content,is disintegrated with other three types(P<0.05).But moisture content of four forest types shows a level-off fluctuation.Apart from the fact that CH4 flux of soil in coniferous and broad-leaved mixed forest has an evident correlation with moisture content(P<0.01),CH4 flux in other three forest types has little correlation with moisture content.In spring and summer,moisture content in Coniferous and broad-leaved mixed forest flies at the peak;autumn and winter fall the bottom.CH4 flux shows different effects on relevant soil nutrient.The following effects of CH4 flux on C:CH4 flux in four forest types has a negative correlation with total organic carbon and carbon of microbial biomass.The correlation between CH4 flux and total organic carbon in soil of broad-leaved evergreen forest shows the most negative(P<0.01);the correlation in mountain coppice and coniferous and broad-leaved mixed forest shows negative(P<0.05).CH4 flux has a weak correlation with carbon of microbial biomass in broad-leaved evergreen forest and deciduous broad-leaved mixed forest.The effect of CH4 flux on N is that in four forest types CH4 flux has a positive correlation with total nitrogen(P<0.01),and so dose it with nitrogen of microbial biomass.CH4 flux in mountain coppice and coniferous and broad-leaved mixed forest has a strong positive correlation with nitrogen of microbial biomass(P<0.05),and broad-leaved evergreen forest and deciduous broad-leaved mixed forest share a weak correlation.The effect of CH4 flux on P is that CH4 flux holds a positive correlation with total phosphorus and available phosphorous.In mountain coppice,CH4 flux has a strong positive correlation with total phosphorus(P<0.05),but the correlation in other three forest types is weak.CH4 flux in broad-leaved evergreen forest has the most evident positive correlation with available phosphorous(P<0.01),mountain coppice and coniferous and broad-leaved mixed forest have a evident positive correlation(P<0.05),but CH4 flux has little correlation with available phosphorus in coniferous and broad-leaved mixed forest and deciduous broad-leaved mixed forest.From the result,CH4 flux in four forest types fluctuated by the coordination of several elements,and soil temperature and total nitrogen are the principle elements causing CH4 flux in Nanling CH4 flux in four forest types has the most negative correlation with soil temperature and total nitrogen.This thesis has laid a theoretical foundation for greenhouse gas emission and reduction of CH4.