硬头黄竹地上生物量分配特征及模型构建

【目的】探究硬头黄竹不同龄级、径级地上生物量分配特征,建立全竹龄和不同竹龄地上单株及各器官生物量模型,准确估算硬头黄竹的林分生物量。【方法】选取了硬头黄竹全径级(1.0~7.0 cm)分布的1、2、3年生硬头黄竹各50株,测定各器官和总生物量。采用11种常用生物量模型,分别对硬头黄竹全竹龄和不同竹龄地上单株和各器官生物量进行拟合,筛选最优生物量拟合方程,并应用模型估算不同龄级、径级林分总生物量。【结果】硬头黄竹地上竹秆、竹枝、竹叶生物量占比分别为84.82%、10.84%、4.34%;不同龄级单位面积林分总生物量差异显著,竹龄为1、2、3 a竹生物量占比分别为31.92%、47.15%、20.93%;4.6~5.5 cm径级各器官和总生物量显著高于其他径级,占林分生物量的62.60%。11种生物量模型均可以较好地模拟硬头黄竹地上单株及各器官生物量;优选出全竹龄硬头黄竹地上单株和各器官生物量模型6个,不同竹龄的硬头黄竹地上单株和各器官生物量模型19个(1 a的6个、2 a的7个、3 a的6个)。【结论】硬头黄竹不同龄级、径级各器官生物量占比均为竹秆>竹枝>竹叶,林分生物量主要集中在2龄级、4.6~5.5 cm径级的竹株。全竹龄和不同竹龄地上单株与各器官生物量拟合模型中幂函数的拟合效果最优,其次是多项式函数和指数函数;地上单株与竹秆生物量模型拟合效果受胸径、株高的影响较大,竹枝、竹叶生物量模型拟合效果与胸径关系更密切。全竹龄硬头黄竹地上单株和竹秆生物量模型拟合效果均优于不同竹龄的模型,不同竹龄硬头黄竹地上竹枝、竹叶生物量模型拟合效果均优于全竹龄模型的。

Aboveground biomass allocation patterns and model construction of Bambusa rigida

【Objective】We built biometric models to improve the estimation accuracy of aboveground biomass and its allocation patterns in Bambusa rigida for different ages,diameter classes and organs.【Method】After selecting B.rigida bamboo pure forests with similar topography,elevation,aspect and slope as the study case,the age and DBH of standing bamboo were investigated.A total of 150 B.rigida individuals(1 a,2 a,3 a)with full-diameter classes(1.0-7.0 cm)were selected,and the biomass of different organs and the total biomass were measured.Eleven types of biomass models were applied to model aboveground biomass for individual bamboos and for different organs of different ages of B.rigida.Taking DBH and height of bamboos,and their combined forms(D,D2,DH and D2H)as independent variables,the R software was used to run the biomass models.The coefficient of determination(R2),root mean square error(RMSE)and mean absolute error(MAE)were used to evaluate the models.Finally,the biomass models with the best statistical performances were selected to estimate the total biomass of different ages and diameter classes.【Result】The biomass of the culm,branch and leaves of B.rigida made up 84.82%,10.84%and 4.34%of the total individual bamboo biomass,respectively.Bamboos with a diameter class of 4.6-5.5 cm made up 62.60%of the stand biomass.All 11 types of biomass models can simulate the aboveground biomass of individual bamboo and organs.A total of 176 fitting equations were obtained,with R2 ranging from 0.480 to 0.975,the RMSE ranging from 0.027-0.769 kg,and the MAE ranging from 0.021-0.589 kg.Six models of the aboveground biomass of individual bamboos and organs of all age classes were selected,and 19 models of aboveground biomass of individual bamboos and organs of different age classes were selected(6 of 1 a,7 of 2 a,6 of 3 a).【Conclusion】The proportion of biomass of different organs in different ages and diameter classes of B.rigida was in the order of culm>branch>leaf.With the increase in age,the proportion of bamboo stalk biomass decreased significantly,while the proportion of bamboo branch biomass increased significantly.In contrast,the proportion of bamboo stalk biomass generally increased,while the proportion of bamboo branches and leaf biomass generally decreased with increasing diameters.The stand biomass was dominated by the age class of 2 a or the diameter class of 4.6-5.5 cm.The fitting effect of the power function was the best,followed by the polynomial function and exponential function.The aboveground biomass of individual bamboos and culms was greatly affected by DBH and plant height,and the biomass of branches and leaves was more closely related to DBH.The model performances of the aboveground biomass models of individual bamboos and culms,regardless of age class,were better than those of different age classes,and the model performances of the aboveground biomass models of branch and leaf,regardless of age class,were better than those of different age classes.In this study,a large number of B.rigida were selected by refining age classes and diameter classes,and the biomass allocation patterns of B.rigida were studied in different diameter classes and age classes.Additionally,various mathematical models were used to construct and select the optimal models.Estimating stand biomass and further obtaining its stock and allocation patterns is important for refining biomass estimation and guiding production and management of bamboo forests.