A Method for the Development of Dynamic Site Index Models Using Height–Age Data from Temporal Sample Plots

Jarosław Socha,Luiza Tymińska-Czabańska

doi:10.3390/f10070542

Abstract

Knowledge of the potential productivity of forest sites is fundamental for making strategic decisions in forest management. Site productivity is usually evaluated using the site index, and therefore the development of site index models is one of the crucial tasks in forest research and forest management. This research aims to develop an effective method for building top-growth and site index models using data from temporary sample plots (TSP). Exploiting the advantages of the generalised algebraic difference approach (GADA), the proposed method overcomes the limitations of the guide curve method that has been to date used in site index modelling using TSPs data and allows to obtain only a set of anamorphic site index curves. The proposed approach enables the construction of dynamic site index models with polymorphism and variable asymptotes. Such models better reflect local, site-specific height growth trajectories and therefore allow more appropriate site index estimation. We tested the proposed method using data collected from 5105 temporary sample plots in Poland. Our results indicate that growth trend estimates using height–age measurements of TSPs may be valuable data for modelling top height growth. For these reasons, the proposed method can be very useful in forest management.

Highlights

Knowledge of the potential productivity of forest sites is fundamental to making strategic decisions in forest management, including those related to species composition and silvicultural treatments, as well as to determining timber yield [1]
Using the site index calculated for the base age of 50 years as the reference level, we found large congruity between growth curves drawn according to the developed model and the local reference congruity between growth curves drawn according to the developed model and the local reference model for Scots pine for the Second Natural Forest Region
We proposed and tested a new approach for the calibration of top height growth and site index models based on measurement data from temporary sample plots (TSP) located in areas with a wide range of local conditions

Summary

Introduction

Knowledge of the potential productivity of forest sites is fundamental to making strategic decisions in forest management, including those related to species composition and silvicultural treatments, as well as to determining timber yield [1]. Site productivity is usually evaluated using the site index, determined using top height at a predetermined age, referred to as base age [2,3,4,5]. The development of site index models is one of the essential tasks in forest management and forest research. Most site index models developed in the 20th century were fitted using base-age-specific parameter estimation, whose primary defect is the dependence of the parameters on the base age [6,8]. The algebraic difference approach (ADA; [9]) is the precursor to the generalised algebraic difference approach (GADA)

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