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Scientia Silvae Sinicae ›› 2013, Vol. 49 ›› Issue (8): 65-74.doi: 10.11707/j.1001-7488.20130810

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Individual Crown Diameter Prediction for Cunninghamia lanceolata Forests Based on Mixed Effects Models

Fu Liyong1, Sun Hua1,2   

  1. 1. Research Institute of Forest Resources Information Techniques, CAF Beijing 100091;
    2. Research Center of Forestry Remote Sensing and Information Engineering, Central South University of Forestry and Technology Changsha 410004
  • Received:2012-11-08 Revised:2013-03-23 Online:2013-08-25 Published:2013-08-17

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Abstract:

An individual crown diameter model was developed based on a data set consisting of 2 461 Cunninghamia lanceolata from 103 plots located in Huangfengqiao state-owned forest farm in Hunan Province. Because of the problem of high correlation among observations taken from the same sample plot located in different levels of site index, the random effects of site index and sample plots to crown diameter were considered, namely, developing nested two levels nonlinear mixed effects canopy model. Base model that used to develop mixed model was selected from 12 commonly used models in forest. In addition to diameter at breast height, the effects of other 12 stand or trees factors to crown diameter were considered. The best random effects combination for formal parameters was determined by indexes of AIC (akaike information criterion) and logarithm likelihood. Three residual variance models of Exponential function, power function and constant plus function were used to decline the heteroskedasticity. Mixed effects model and traditional regression model were compared and evaluated finally. Results showed that crown diameter-diameter model of logistic formal had a better fit effect and was selected as base model; diameter at breast height, under branch height, height and dominant height of plot were significant factors in crown diameter model; power function had a better ability to decline the heteroskedasticity; comparing to site index, the nested effects of site index and plot played more important role in crown diameter model; the prediction efficiency of the nested two level of model (15) was higher than site index level and population average level, and obviously improved comparing with model (13). This article was mainly emphasize method research, it can be used similar method that proposed in this study to built canopy with model for other tree species.

Key words: Cunninghamia lanceolata, individual crown diameter model, nested two level nonlinear mixed effects model, heteroskedasticity

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