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Scientia Silvae Sinicae ›› 2023, Vol. 59 ›› Issue (10): 50-56.doi: 10.11707/j.1001-7488.LYKX20220076

• Research papers • Previous Articles     Next Articles

A New Activation Function Based on Richards Equation for Tree Height-Diameter Deep Neural Network Model of Abies nephrolepis

Qigang Xu1,2,3,Xiangdong Lei1,3,*,Yu Zheng2,Xingguo Hu4,Yuancai Lei1,3,xiao He1,3   

  1. 1. Institute of Forest Resource Information Techniques, Chinese Academy of Forestry Beijing 100091
    2. East China Academy of Inventory and Planning, National Forestry and Grassland Administration Hangzhou 310000
    3. Key Laboratory of Forest Management and Growth Modelling, National Forestry and Grassland Administration Beijing 100091
    4. Wangqing Forestry Bureau of Jilin Province Wangqing 133200
  • Received:2022-02-14 Online:2023-10-25 Published:2023-11-01
  • Contact: Xiangdong Lei

Abstract:

Objective: An activation function based on theoretical growth equation (Richards formula) is proposed to solve the problem that the output of neural network algorithm does not accord with biological laws in forest growth modeling, in order to provide a new idea and method for the application of neural network in forest growth modeling. Method: Using the stem analysis data of 96 Abies nephrolepis trees in Wangqing Forestry Bureau of Jilin Province, the traditional nonlinear regression model, the deep neural network tree height-DBH model based on ordinary activation function and the new deep neural network tree height DBH model based on Richards activation function were established respectively. Result: Compared with the traditional nonlinear regression model, R2 of the deep neural network model increased by 0.175%, root mean squared error (RMSE) and mean absolute error (MAE) decreased by 2.282% and 4.011%, respectively. Compared with the deep neural network model of ordinary activation function, the new model has obvious tree height asymptote, which is more fitted with the biological law. Conclusion: A neural network activation function based on Richards formula is proposed, which has the following advantages: 1) There must be a maximum value for the output. 2) The output must be greater than 1.3 with a reasonable ANN structure. 3) The new method can take the parameters fitted by the traditional regression method as the input of the neural network model, so that the neural network training can obtain a priori knowledge.

Key words: deep neural network, activation function, theoretical growth equation, height-diameter model

CLC Number: