采伐干扰对华北落叶松细根生物量空间异质性的影响

以华北落叶松天然林为研究对象,选择采伐干扰林分(样地A)和未采伐干扰林分(样地B),利用根钻法分3层(0—10cm,10—20cm,20—30cm)获取各径级细根(≤1mm、1—2mm、2—5mm3级活细根,≤2mm死亡细根)生物量数据。采用地统计学变异函数和经典统计相结合的数据分析方法对采伐干扰造成的细根生物量空间异质性的变化进行定量研究。主要研究结果如下:采伐干扰林分样地A各经级细根生物量均值减少;同一土层相同径级细根生物量样地A与样地B相比差异显著(P<0.05);不同土层的细根生物量异质性具有显著差别(P<0.05)。0—10cm土层,未采伐干扰林分≤1mm细根生物量呈现较明显的空间自相关变异,采伐干扰林分则表现为随机性变异特征,采伐干扰导致≤1mm细根生物量空间分布特征更加复杂(分维数D=1.978);10—20cm土层,采伐干扰林分各径级细根生物量异质性程度明显降低,只有未采伐干扰林分的5.4%—88.9%。20—30cm土层,未采伐干扰林分≤1mm细根生物量在较小尺度范围(<2.9m)表现出明显的空间自相关变异(结构方差比86.1%),受采伐干扰林分各径级细根生物量异质性程度只有未采伐干扰林分的8.9%—45.9%,且呈现随机性变异。各径级细根生物量空间异质性的垂直分异均表现为随土层深度的增加异质性强度明显降低。

Effects of cutting disturbance on spatial heterogeneity of fine root biomass of Larix principis-rupprechtii

This study was conducted in Larix principis-rupprechtii forests,which located in Guandi Mountain,Shanxi Province,China.Two plots(32m×32m) were placed.Plot A was disturbed stand while plot B undisturbed.Basic data of fine root biomass with various diameters were collected from three depths(0—10cm,10—20cm and 20—30cm) of soil layers via root drilling methods.The fine roots were separated into live and dead fine root(≤2mm).The live fine roots were classified into three categories(≤1mm,1—2mm,2—5mm).The spatial heterogeneity of fine root biomass was analyzed based on theory and methodology of spatial pattern analysis in geostatistics.By comparing the fine root biomass at same soil depth in different stand,fine root biomass was higher in undisturbed stand(plot B) with great difference,which also has high spatial heterogeneity.After cutting disturbance,fine root biomass became lower with smaller difference and the spatial heterogeneity intensity of fine root biomass became weaker.In different soil layer,the heterogeneity of fine root biomass changed significantly(P<0.05).Results showed:(1) At 0—10cm soil depth,fine root(≤1mm,1—2mm,2—5mm and ≤2mm dead root) biomass decreased respectively 8.14%,48.29%,47.96% and 74.21%.Most variation of fine root biomass was spatially explained in undisturbed stand.Spatial heterogeneity of fine root biomass performed clearly randomly variation after disturbance.Spatial distribution of fine root(≤1mm)biomass became more complicated in disturbed stand.(2) At 10—20cm soil depth,fine root(1—2mm,2—5mm and ≤2mm dead root) biomass decreased respectively 60.53%,67.56%,67.32%.Fine root biomass showed weaker spatial heterogeneity intensity in disturbed stand,which was only 5.4%—88.9% spatial heterogeneity in undisturbed stand.(3) At 20—30cm soil depth,fine root(1—2mm,2—5mm and ≤2mm dead root) biomass decreased respectively 127.90%,44.22%,355.19%.In both plot A and B,fine biomass of all classes changed significantly(P<0.05).Fine root biomass(≤1mm) remained mainly spatial autocorrelation variation,with structural variance proportion 86.1% at the range of 0.5—2.9m.After cutting disturbance,spatial heterogeneity became weaker and performed clearly randomly variation.Vertical differentiation appeared that spatial heterogeneity of fine root biomass decreased with the increasing of soil depths in two stands.