Charaeteristies Of CO₂Flux In A Phylloetachys Edulis Ecosystems

With its remarkable advantages of rapid growth, high yield, wide application and goodeconomic returns, Phyllostachys edulis has been one of the most extensively distributed baboo inChina,especially in South China. In this paper,open path eddy covariance system and automatedobserving systems of gradient weather were used to determine the characteristics of CO₂flux and itsresponse mechanism to environmental factors in a ecosystem of Phyllostachys edulis stands in Anjifrom December2010to November2011. At the same time,the carbon absorption capacity of systemwas estimated. The study contributed to the research of carbon cycle of Phyllostachys edulis and theunderstanding of carbon sink of forests in China especially the bamboo forest.The results showed that:1.CO₂flux had obvious diurnal and yearly variations. First of all,the average diurnal variationwas basically the same in each month and the value of CO₂flux was negative in the daytime as well aspositive in other times. The variability of CO₂flux was large,which showed that the maximum ofnegative value was about-0.303to-0.495mg·m^-2·s^-1from November to June except March andApril,about-0.521to-0.596mg·m^-2·s^-1in the other months. Secondly,diurnal cumulative value of CO₂flux floated between^-14.9to11.2mg·m^-2·d^-1, mean as-3.7±3.49g mg·m^-2·d^-1, diurnal cumulative valueof CO₂flux was negative at most of days in the year, The days about86.3%of a year were negativewith diurnal cumulative value of CO₂flux.2.The seasonal variation of GEE was basically consistent with NEE. The monthly NEE wereall negative,and the maximum is July(-99.3gC·m^-2·mon^-1)while the minimum is January(-24.9gC·m^-2·mon^-1).Differently,the monthly RE varied as a"single peak"curve in the year and came tominimum in February (63.3671gC·m^-2·mon^-1)whereas reached its maximum in July(92.15gC·m^-2·mon^-1).3.CO₂flux was mainly affected by photosynthetic active radiation(PAR)in the daytime andfitted the Michaelis-Menten model well.With the increase of PAR,the carbon sink was increased,Usedthe NEE in the daytime fitted the Michaelis-Menten model month by month,we got the correlationcoefficient between0.333and0.606. The response of CO₂flux to PAR was different at differentseasons,the second half year of2011got higher αand Nes than first half year. At nighttime,therespiration of ecosystem had correlation with soil temperature and soil water content(SWC).Night-timeCO₂flux showed an exponential relationship with soil temperature and SWC at5cm depth, amix-model with temperature and water is better fitted than model with only water or temperature. In themonth scale,the respiration of ecosystem was related to SWC as a quadratic parabola opening upward.4.NEE,RE and GEE were effected by air temperature,VPD and SWC obviously on month scale.On month scale,GEE has strong relationship with temperature and VPD, RE with air temperatureshowed significant linear correlation while NEE and air temperature related as a quadratic curve. The total amount of NEE, RE, GEE were respecti vely-6.02t C-m^-2a^-1,9.32t C-m^-2a^-1,-15.95t C-m^-2a^-1.