衡南县油茶林立地质量评价研究

Site quality evaluation of Camellia oleifera forest in Hengnan County

【目的】对湖南省衡南县各立地条件下油茶(Camellia oleifera)林的立地质量进行评价,以确定油茶的最适生长环境。【方法】以2017年湖南省衡南县国家森林资源二类调查数据中365个油茶林小班的海拔、坡度、坡向、坡位、土壤类型、土层厚度6个立地因子为依据,采用主成分分析法提取出主要立地因子并划分立地类型;以冠幅为自变量,选择6个基础模型间接预估油茶果的单株产量,并将其作为油茶林立地质量的评价指标,对衡南县油茶林各立地类型进行质量评价及立地质量等级划分。【结果】主成分分析表明,对油茶林生长影响最大的立地因子为海拔、坡向和土层厚度,将其分别作为油茶林三级立地分类因子,可将衡南县油茶林划分为3个立地类型小区、15个立地类型组和36个立地类型。6个间接预估油茶果单株产量的基础模型中,Logistic模型拟合的确定系数(R2=0.868)和预估精度(P=98.57%)最高,均方根误差(RMSE=0.219)和残差平方和(SSE=1.974)最小,故将其作为油茶果产量预估的最佳模型,以其预估结果进行立地质量评价。立地质量评价结果显示,立地质量等级Ⅰ为油茶种植最适宜区,其面积占比0.83%,平均单株产量为3.50 kg;立地质量等级Ⅱ为油茶种植适宜区,其面积占比57.46%,平均单株产量为3.07 kg;立地质量等级Ⅲ为油茶种植较适宜区,其面积占比39.75%,平均单株产量为2.95 kg;立地质量等级Ⅳ为油茶种植不适宜区,其面积占比1.96%,平均单株产量为2.64 kg。【结论】衡南县大部分地区适宜油茶生长,油菜种植适宜区及以上的面积占比高达58.29%,应作为衡南县油茶种植的重点区域。

【Objective】The site quality of Camellia oleifera forest under different site conditions in Hengnan,Hunan was evaluated to determine its optimum growth environment.【Method】Based on six site factors of altitude,slope,aspect,slope position,soil type and soil layer thickness of 365 C.oleifera forest subcompartments in the forest management inventory in 2017,the principal component analysis method was used to extract main site factors and divide site types.Using crown width as the independent variable,six basic models were selected to indirectly estimate yield of C.oleifera,which were used for evaluation of site quality and division of grade classes.【Result】According to principal component analysis,altitude,aspect and soil layer thickness were the most important site factors affecting growth of C.oleifera forest.Using them,C.oleifera forest in Hengnan were divided into 3 site type plots,15 site type groups and 36 site types.Among the six basic models for indirect prediction of yield per plant,the Logistic model fitting had the highest coefficient of determination(R2=0.868)and precision of prediction(P=98.57%)and the smallest root mean square error(RMSE=0.219)and sum of residual squares(SSE=1.974).Thus,it was the best model for predicting yield of C.oleifera.The evaluation results showed that the site quality gradeⅠwas the most suitable for C.oleifera planting,accounting for 0.83%with an average yield of 3.50 kg per plant.The site quality gradeⅡwas suitable for C.oleifera planting,accounting for 57.46%with an average yield of 3.07 kg per plant.The site quality gradeⅢwas less suitable for C.oleifera planting,accounting for 39.75%with an average yield of 2.95 kg per plant.The site quality gradeⅣwas unsuitable for C.oleifera planting,accounting for 1.96%with an average yield of 2.64 kg per plant.【Conclusion】Most areas in Hengnan were suitable for growth of C.oleifera,and the key areas for C.oleifera planting accounted for 58.29%of the total area.