This study was conducted in a fire-prone region in the Greater Xing'an Mountains,the primary forested area of northeastern China.We measured soil respiration and the affecting soil factors,i.e.,soil microbial biomass and soil moisture,within an experimental plot of Larix gmelinii Rupr.A low-intensity,prescribed fire was applied as the treatment.Traditional descriptive statistics and geostatistics were used to analyze the spatial heterogeneity of soil respiration and the response of respiration to fire disturbance.Coefficients of variation(CVs) for pre-fire and post-fire soil respiration were 23.4 and 32.0 %,respectively.CVs for post-fire soil respiration increased significantly,with a moderate variation of all CVs.Soil respiration pre-fire was significantly correlated with soil microbial biomass carbon,biomass nitrogen,and soil moisture(W);post-fire soil respiration was not correlated with these factors.From the geostatistical analyses,the C_0+C(sill) for post-fire soil respiration increased significantly,indicating that the post-fire spatial heterogeneity of soil respiration increased significantly.The nugget effect(nc) of soil respiration and the affecting factors pre-fire and post-fire disturbance were in the range of 12.5–50 %,with strong spatial autocorrelation.Fire disturbance changed the components of spatial heterogeneity,and the proportion of functional heterogeneity increased significantly post-fire.The ranges(a) for pre-fire and post-fire soil respiration were 81.0 and 68.2 m,respectively.The homogeneity of the distribution of post-fire soil respiration decreased and the spatial heterogeneity increased,thus the range for postfire soil respiration decreased significantly.The fractal dimension(D) for soil respiration increased post-fire,the spatial heterogeneity of soil respiration affected by random components increased,indicating that the change in spatial heterogeneity of post-fire soil respiration should be considered within the scale of the forest stand.Following Kriging interpolation,the increase
森林火灾是森林生态系统中重要的干扰,对碳循环和碳平衡具有影响。林火作为大兴安岭森林生态系统中主要的干扰因子,直接影响区域的净初级生产力NPP(net primary productivity)。林火的发生使NPP迅速下降,改变了区域碳平衡。以多时相遥感数据为基础,利用CASA(Carngie-Ames-stanford-Approach)模型估算大兴安岭北部地区未过火区和过火区植被NPP变化。结果表明:1987年6月,未过火区植被NPP为145 g C m-2,轻度过火区为74 g C m-2,中度过火区为58 g C m-2,重度过火区植被NPP为38 g C m-2,火干扰后NPP分别降低了49%、60%、73%;1999年8月,火干扰12 a后,过火区NPP是未过火区NPP的96%以上,NPP恢复迅速,基本达到未过火区水平。2009年8月,火干扰22 a后,过火区NPP是未过火区93%以上,与火干扰12 a时相比,下降3%。虽然NPP增速下降,但是NPP总量增加,生产力也与未过火区基本处于同水平。
