采用地统计学方法对水曲柳人工纯林表层根量的估计

The estimate of root biomass in upper soil layer of Fraxinus mandshurica plantation by geostatistics method

采用地统计学的变异函数分析方法定量研究了水曲柳纯林表层根量的空间异质性特征,利用地统计学的克里格内插法结合定积分,对水曲柳纯林表层(0～10 cm)各类型根量进行了估测。结果表明:1)水曲柳细根(<2 mm)、粗根(≥2 mm)、活根和土壤总根变异函数曲线的理论模型符合球状模型,其它植物活根符合指数模型,水曲柳及其它植物死根符合线性模型。水曲柳及其它植物死根的空间变异主要是由随机性因素引起;水曲柳细根、粗根、活根、其它植物活根和土壤总根的空间变异主要是由结构性因素引起,且空间自相关程度均属中等(空间结构比在2 5 %和75 %之间)。水曲柳粗根的空间变异尺度为13.2 m,水曲柳细根、水曲柳活根、土壤总根和其它植物活根的空间变异尺度均大于33.9m。根据理论模型的拟合参数估计,水曲柳细根、水曲柳活根和土壤总根的空间变异尺度为6 1m,其它植物活根为183m。(2 )平均值成对二样本t检验结果表明,变异函数分析结果基础上的克里格内插法适用于水曲柳样地各空间位置处各类型根量的估计。利用此估计值,拟合其与位置坐标值之间的多元回归关系均为二元十次余弦级数多项式。利用此多项式,通过定积分的方法(积分区间为整块样地的大小) ,估计出水曲柳纯林表层根量为1.5 92 6 t/ hm2 ,水曲柳细根为0 .6 86 5 t/

Semivariance analysis of Geostatistics was employed in the quantitative study of the spatial heterogeneity of root biomass in upper layer of soil under 14-year-old Fraxinus mandshurica plantation stand. The method used for the estimation of the root biomass was kriging interpolation of Geostatistics and definite integral. The results showed that (1) the semivariograms of fine root(<2mm), coarse root (≥2mm) and living root of Fraxinus mandshurica and total root biomass were best described by spherical model, while that of living root of other plant species, and the dead root of Fraxinus mandshurica and other plant species, submited exponential model and linear model, respectively. The spatial variability of dead root of Fraxinus mandshurica and other plant species was primarily the result from random factors, while that of fine root, coarse root and living root of Fraxinus mandshurica, living root of other plant species, and total root was mainly caused by structural factors. The spatial heterogeneity degree of those indices induced by structural factor was moderate (with spatial structural ratio between 25% and 75%). The scale of spatial heterogeneity in coarse root of Fraxinus mandshurica was 13.2 m. That of fine root and living root of Fraxinus mandshurica, total root and living root of other plant species was greater than 33.9 m. Estimation from the parameter of theoretical models indicated that the scale of spatial heterogeneity in fine root and living root of Fraxinus mandshurica, as well as total root was 61m, and that of living root of other plant species was 183 m. (2) The t-test of pair samples showed that the kriging interpolation, based on the results of semivariance analysis, could be used to estimate the root biomass on every location in Fraxinus mandshurica plantation stand. The relationship between those estimated root biomass and the values of its corresponding coordinates was best fitted by bivariate order 10 cosine series polynomial. Based on the result of definite integral to those polynomials (integral range was limited to plot size), the total root biomass of the stand was 1.5926 t/hm^2; the fine root biomass, the coarse root biomass, and the living root of Fraxinus mandshurica was 0.6865, 0.1913, 0.9105 t/hm^2, respectively; the dead root of Fraxinus mandshurica and other plant species was 0.3303 t/hm^2, the living root of other plant species was 0.2127 t/hm^2. Using the kriging interpolation method of Geostatistics, combined with multiple regression and definite integral, provide a new optimal alternative for the estimation of root biomass in Fraxinus mandshurica plantation stand.