基于频谱分析用针刺仪测定树木年龄的算法

Tree Age Estimation Algorithm Based on Spectrum Analysis by Resistograph

[目的]研究离散谱分析在针刺仪抗钻阻力序列中的应用,为活立木年龄的微损测定提供方法。[方法]以山西省羊圈沟林场落叶松为对象,使用针刺仪在同一水平位置不同方向钻入落叶松,获取323组抗钻阻力值序列作为研究样本,并在针刺位置5 cm内截取104个圆盘作为参考样本。选择恰当的窗口,将抗钻阻力值序列去趋势后,进行离散谱分解,寻找代表年度变化的谐波,将其周期数的一半作为树木年龄估计值。并将频谱分析算法估计的树木年龄以及针刺仪自带软件DECOM自动判定年龄分别与相应的圆盘年轮数进行成对数据t检验。[结果]根据活立木的胸径大小来选择窗口参数Wid,将频谱分析算法应用于323组活立木的抗钻阻力序列,该算法估计树木年龄与实测年龄非常接近。频谱分析算法估计年龄的最小相对误差为0,最大相对误差为27.98%,平均相对误差为-0.35%。经过成对数据t检验得到t值为0.85,说明该算法估计树木年龄均值与真实年龄均值之间无显著差异。而针刺仪自带DECOM软件自动分析估计年龄结果相对误差较大,最小相对误差为-7.69%,最大相对误差达到-84.78%,平均相对误差达到-40.49%,与实际年龄进行成对数据t检验得到t值为20.25,差异显著。[结论]频谱分析应用于针刺仪抗钻阻力值序列来估计树木年龄,能够比较准确地估计落叶松年龄,提高了针刺仪测定活立木年龄的精度,为活立木年龄的微损测定提供了一种有效途径。

[Objective] To study the application of discrete spectrum analysis in the Resistograph drill resistance sequence, and provide a method and basis for estimating the age of standing trees. [Method] Taking Larix principisrupprechtii in Yangjuangou Forest Farm of Shanxi Province as the research object, 323 sets of drilling resistance series obtained by Resistograph drilling L. principis-rupprechtii in the same horizontal position and different directions was used as the research sample, and 104 stem discs were taken within 5 cm of the drilling position as reference samples. After detrending the Resistograph drill resistance sequence, the discrete spectrum decomposition was carried out to find the harmonic representing the annual change, and half of its period duration was taken as the tree age estimation. The results estimated by spectrum analysis algorithm, or auto-recognized by DECOM software were analyzed with the corresponding number of disc rings using paired data test. [Result] According to DBH size of living trees, the window parameters were selected, and the spectrum analysis algorithm was applied to the drilling resistance series of 323 groups of living trees, the algorithm estimating tree age closed to the actual age. The relative error distribution of the algorithm was mostly between-10% and 10%, the minimum relative error was 0, the maximum relative error was 27.98%, and the average relative error was-0.35%. Through paired data t-test, it was found that tvalue was 0.85, indicating that there was no significant difference between the mean age estimated by the algorithm and the true mean age of trees. The relative error of the automatic analysis by DECOM software was large, mostly concentrated between-20% and-60%. The minimum relative error, the maximum relative error and the average relative error were-7.69%,-84.78% and-40.49%. Through paired data t-test, it was found that t-value was 20.25, indicating that there was significant difference between the mean age estimated by DECOM software and the mean tree age of trees. [Conclusion] The method of applying spectrum analysis to the drilling resistance data sequence can accurately estimate the age of L. principis-rupprechtii, improve the accuracy of measuring the standing age by Resistograph, which provides an effective way for micro-damage measurement of standing tree age.