基于微根管法的亚热带常绿阔叶林细根直径分布、空间变异与取样数量估计

摘要

By using the minirhizotrons method, 96 minirhizotrons were installed in a subtropical ever-green broad-leaved forest located at Sanming, Fujian province. We studied the spatial heterogeneity of fine root morphological characteristics and their changes with fine root diameter. We also estimated the sample sizes required for accurately determining various fine root variables. The results showed that:1) The fine roots observed by minirhizotrons were small in diameter, 88% of the root number was≤0. 5 mm in diameter, the roots with diameter >1 mm only accounted for 3%; 2 ) The distribution characteristics of fine root length and volume along with the change in root diameter were different:for roots with diameter≤1 mm, its length accounted for 95% of total root length, and its volume accounts for only 50% of the total root volume;3 ) The Shapiro-Wilk test showed that root variables ( fine root length density and fine root volume density) in different soil depth did not conform normal distribution, with positive skew;4 ) The statistical simulation analysis of Monte Carlo indicated that under the condi-tion with 95%confidence leve1 and 80% estimated precisions, the sampling number of fine root length density was 79;but under the similar measured condition the required sample sizes of fine root volume density were far more greater than the sampling number (96) in our study. Traditional minirhizotrons method could only observe roots with small diameter, when it was used to estimate root parameters, it was easy to cause inaccurate estimate as a result of less sampling number. In the future study, the ob-served range of minirhizotrons should be amplified or Rhizotrons should be applied.%采用微根管法,在福建省三明米槠天然常绿阔叶林内布设96根微根管,分析细根形态特征随细根直径的变化及其空间变异,并估计细根变量所需的取样数量。结果表明：1)微根管法观测的细根直径较小,88%的根数量其直径≤0．5 mm,>1 mm的根数量仅占3%；2)细根的根长和体积随根直径分布的特点不一致：≤1 mm的根其根长占总根长的95%,而体积只占总根体积的50%；3) Shapiro-Wilk检验表明,细根根长密度和根体积密度在不同土层均是非正态分布,且均呈右偏分布；4)蒙特卡罗统计模拟分析表明：在95%置信水平、80%估计精度要求下,微根管法测定细根根长密度时需要的取样量达79个；而测定类似条件下细根体积密度所要求的取样量则远超出本研究的最大采样量(96个)。传统的微根管法仅能观测到直径较小的根,在估计细根参数时易因取样体积不足导致估计不准确,在今后的研究中,应扩大微根管的观测范围或采用根窗法。