基于不同浓度变量的温带落叶阔叶林CO2储存通量的误差分析

利用帽儿山温带落叶阔叶林通量塔8层CO₂/H₂O浓度廓线的测定数据，比较分析了基于不同浓度变量\密度(ρ_c)、摩尔分数(c_c)和混合比(χ_c)\]计算CO₂储存通量(F_s)的误差.结果表明： 通量观测的控制体积内部干空气储存量不为常数，其波动可引起CO₂分子进出控制体积，即干空气储存通量调整项(F_sd)的变化.在夜间以及昼夜转换期，F_sd相对于涡动通量而言较大，忽略F_sd将为森林与大气之间净CO₂交换量的计算带来误差.大气水热过程对F_s计算引起的误差包括3方面：空气温度变化引起的误差最大，比大气压强(P)的影响高1个数量级；水蒸气的影响在温暖湿润的夏季大于P的影响，但在寒冷干燥的冬季则相反; P的效应在全年均较低.基于ρ_c、c_c和χ_c计算F_s分别平均高估CO₂有效储存通量(F_{s_E})8.5%、0.6%和0.1%.在通量计算过程中，建议选择对大气水热过程守恒的χ_c计算F_s.

Effects of short-term planting of three transgenic Bt rice lines on soil microbial biomass and soil nematode assemblage

Using the measurement data from an 8-level vertical profile of CO₂/H₂O in a temperate deciduous broadleaved forest at the Maoershan Forest Ecosystem Research Station, Northeast China, this paper quantified the errors of CO₂ storage flux (F_s) calculated with three scalar variables, i.e., CO₂ density (ρ_c), molar fraction (c_c), and molar mixing ratio relative to dry air (χ_c). The dry air storage in the control volume of flux measurement was not a constant, and thus, the fluctuation of the dry air storage could cause the CO₂molecules transporting out of or into the control volume, i.e., the variation of the dry air storage adjustment term (F_sd). During nighttime and day-night transition periods, the relative magnitude of F_sd to eddy flux was larger, and ignoring the F_sd could introduce errors in calculating the net CO₂ exchange between the forest ecosystem and the atmosphere. Three error sources in the F_s calculation could be introduced from the atmospheric hydrothermal processes, i.e., 1) air temperature fluctuation, which could cause the largest error, with one order of magnitude larger than that caused by atmospheric pressure (P), 2) water vapor, its effect being larger than that of P in warm and moist summer but smaller in cold and dry winter, and 3) P, whose effect was generally smaller throughout the year. In estimating the effective CO₂ storage (F_{s_E}), the F_s value calculated with ρ_c, c_c, and χ_c was overestimated averagely by 8.5%, 0.6%, and 0.1%, respectively. It was suggested that in the calculation of F_s, adopting the χ_c conservative to atmospheric hydrothermal processes could be more appropriate to minimize the potential errors.