| Larix gmelinii forest is the important forest ecosystem of northern coniferous forest,which is mainly distributed in cold and temperate,frozen soil and wetland?swamp?.The strong development of cold and wet environment forms a unique larch ecosystem,which is sensitive to global climate change.CH4 is one of the greenhouse gas,which do the greater contribution to increase of atmosphere temperature.The study of CH4 concentration and its environmental control mechanism is of great significance to the study of global carbon cycle and climate change?50° 49'-50° 51'N,121° 30'-121° 31'E?in the Daxinganling Forest Ecosystem in Inner Mongolia.CH4 concentration and atmospheric humidity,soil respiration and the ambient temperature were measured at the height of 40 cm from the ground by FMA-tatic chamber method in the study area.The diurnal and seasonal changes of CH4 concentration and its influencing mechanism of Larix gmelinii forest were studied.The results show:?1?The CH4 concentration diurnal variation of Larix gmelinii in the growing season from May to October showed a single valley curve,and the CH4 concentration decreased with the increase of temperature.The maximum and minimum values appeared at 1:00 and About 14:00.The diurnal variation of CH4 concentration has lower effects of air humidity.?2?The CH4 concentration seasonal variation showed a tendency to decrease first and then increase.The average CH4 concentration was 1.350mg·m-3 in May,and as temperature goes higher,its value goes down.The lowest mean value appeared in July,was 1.330mg·m-3,and then its value goes higher until November,its value was 1.384mg·m-3.The seasonal variation of CH4 concentration in Larix gmelinii decreased with the increase of air temperature:y=7E-07x3+1E-05x2-0.0018x+1.3583?R2=0.6385,p<0.01,Bi= 0.661,RMsE=13.625?.The seasonal variation of CH4 concentration of Larix gmelinii showed the trend of decreasing first and then increasing with the increase of air humidity.Air humidity10446.43mg·m3 is the critical value of CH4 concentration change.When the air humidity is lower than 10446.43mg·m-3,the CH4 concentration of Larix gmelinii ecosystem is decreasing with the air humidity increased.When the air humidity is higher than 10446.43mg-m",the CH4 concentration is increasing with the air Humidity increased.Its correlation:y=6E-10x2-1E-05x+1.3956?R2=0.6355,p<0.01,Bi=0.409,RMSE=14.139?.?3?Using regression analysis,a binary linear regression model is established:y=b+b1x1+b2X2,x1 is temperature,x2 is humidity.The results show that temperature is the most important environmental factor affecting CH4 concentration.The second factor is humidity.The established binary linear regression model is:y=1.362-0.001x1-6.482E-7x2.The aerobic forest soil showed "sink" of the atmosphere CH4,The variations value range of soil CH4 absorption fluxes were 0.0023?0.0416?g·m-2·s-1,0.0027-0.0466?g·m-2· s-1 and 0.0022?0.0426?g·m-2· s-1 in first,mid to late August during growing season.The corresponding soil CH4 uptake range were 0.032mg/d?0.575mg/d,0.037mg/d?0.644mg/d and 0.030mg/d?0.589mg/d. |
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