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Segmented taper equations with crown ratio and stand density for Dahurian Larch (Larix gmelinii) in Northeastern China

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Journal of Forestry Research 2011年第3期22卷 347-352页

作者： JIANG Li-chun LIU Rui-long College of Forestry Northeast Forestry University 26 Hexing roadHarbin 150040 Heilongjiang Province P.R. China.

Segmented taper equation was selected to model stem profile of Dahurian larch （Larix gmelinii Rupr.）. The data were based on stem analysis of 74 trees from Dailing Forest Bureau in Heilongjiang Province, Northeastern China. Two taper equations with crown ratio and stand basal area were derived from the Max and Burkhart’s （1976） taper equation. Three taper equations were evaluated：（1） the original equation, （2） the original equation with crown ratio, and （3） the original equation with basal area. SAS NLIN and SYSNLIN procedures were used to fit taper equations. Fit statistics and cross-validation were used to evaluate the accuracy and precision of these models. Parameter estimates showed that the original equation with inclusion of crown ratio and basal area variables provided significantly different parameter estimates with lower standard errors. Overall fit statistics indicated that the root mean square error （RMSE） for diameter outside and inside bark decreased respectively by 10% and 7% in the original model with crown ratio and by 12% and 7.2% in the original model with basal area. Cross-validation further confirmed that the original equation with inclusion of crown ratio and basal area variables provided more accurate predictions at the lower section （relative heights, 10%） and upper section （relative heights, 50%） for both outside and inside bark diameters.

关键词： basal area crown ratio Larix gmelinii nonlinear regression taper equations

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Comparison of stem volume estimates from terrestrial point clouds for mature Douglas-fir(Pseudotsuga menziessi(Mirb.)Franco)

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Information Processing in Agriculture 2023年第3期10卷 334-346页

作者： Rong Fang Bogdan M.Strimbu Forest Engineering Resourcesand Management DepartmentOregon State UniversityCorvallisOR 97333 ORUSA

As a complement to traditional estimates of stem dimensions from numerical models,terrestrial light detection and ranging(Lidar)provides direct stem diameter and volume values using cylindrical models constructed from point *** study used two approaches to estimate total stem volume using Lidar and compared them with two empirical equations,one used by the Forest Inventory Analysis in the Pacific Northwest(FIA-PNW)and one based on a taper *** fitted point clouds of 10 Douglas-fir with three sets of cylinder models that are distinguished by their segment length(i.e.0.5 m,1 m,and 2 m),then developed three taper equations based on the point-cloud-based diameter estimated *** estimated the total stem volume of the tree with eight models:six-point cloudbased(*** taper and three cylinders)and two ***,we used simulations to extrapolate the volume estimations of various methods for different diameters at breast height(DBH)*** found that all the point-cloud-based taper equations were similar in their performance(R2¼0:94,RMSE=4.6 cm)and produced mean volume estimates greater than mean estimates of the existing *** cylinder models produced 11–16%greater mean volume estimates than the FIA-PNW estimate,with the 0.5 m segment length producing the greatest values,followed by the 1 m and 2 m segment *** simulated data suggested that the mean volume estimates of a given DBH class are different when using different computation *** revealed a combined effect of the computation methods and the DBH class on the mean volume *** conclude that the point-cloud-based taper equations,after being symmetrically calibrated,would be consistent with the regional stem volume estimates,whereas the cylinder models would be better in estimating individual stem *** constructing Lidar-based cylinder models in future applications,cylinder segment length would need to be adjusted to the length and DBH of the stem

关键词： Lidar Cylinder models Cylinder segment length taper equations Forest inventory and analysis

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