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FOREST RESOURCES WANAGEMENT ›› 2020, Vol. 0 ›› Issue (1): 151-157.doi: 10.13466/j.cnki.lyzygl.2020.01.019

• Technical Application • Previous Articles     Next Articles

Stem Shape Curves Simulation for Larixprincipis-rupprechtii Using Quantile Regressions

Lihua FU1, Jinchao HOU1, He SUN2, Hezhi WANG3, Qiang LIU4, Shun CHENG1()   

  1. 1. Saihanba Mechanized Forestry Farm of Hebei,Chengde,Hebei 068466
    2. World Bank Loan Project Management Center,National Forestry and Grassland Administration,Beijing 100714
    3. Academy of Forest and Grassland Inventory and Planning,National Forestry and Grassland Administration,Beijing 100714
    4. College of Forestry,Agricultural University of Hebei,Baoding,Hebei 071000
  • Received:2019-11-25 Revised:2019-12-16 Online:2020-02-28 Published:2020-05-18
  • Contact: Shun CHENG E-mail:chshaaaa@163.com

Abstract:

Stem shape is an important index to reflect the external shape of stem and it is also an important basis for evaluating the value of trunk.The taper equation is an important quantitative index to describe the quality of tree stem shape.The accuracy of its simulation of stem shape directly determines the estimation of trunk volume and forest volume.In this study,four simple taper equations were used to estimate the stem shape of planted Larixprincipis-rupprechtii and the model fit and validation were assessed byadjusted determination coefficient(Ra2),root mean square error(RMSE),mean error(ME)and absolute mean error(MAE).The optimal model was selected and the taper shape of Larixprincipis-rupprechtii was modelled by using quantile regression technology.Result showed that Kozak equation has the best fitting result(Ra2=0.934, RMSE=1.985cm)and the validation result(ME=0.125cm, MAE=1.212cm)on the stem shape among the four simple taper equations.Thus,the taper shape of Larixprincipis-rupprechtii was established by using quantile regression technology based on Kozak equation.Compared with the basic model,the goodness-of-fit of quantile regression model was improved.When the quantile is set to 0.1,the model has a better fitting effect on the stem shape near the lower and upper part of trunk,when the quantile is set to 0.5,the model has a better fitting effect on the trunk at the middle part of trunk,and when the quantile is set to 0.9,the model has a better fitting effect on the base of trunk.It can be seen that quantile regression technology makes the model more flexible.

Key words: quantile regression, taper curve, Saihanba machinery forest farm, Larixprincipis-rupprechtii

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