Taper Function for Pinus nigra in Central Italy: Is a More Complex Computational System Required?
Open Access
- 5 April 2020
- Vol. 11 (4), 405
- https://doi.org/10.3390/f11040405
Abstract
Stem tapers are mathematical functions modelling the relative decrease of diameter (rD) as the relative height (rH) increase in trees and can be successfully used in precision forest harvesting. In this paper, the diameters of the stem at various height of 202 Pinus nigra trees were fully measured by means of an optical relascope (CRITERION RD 1000) by adopting a two-steps non-destructive strategy. Data were modelled with four equations including a linear model, two polynomial functions (second and third order) and the Generalised Additive Model. Predictions were also compared with the output from the TapeR R package, an object-oriented tool implementing the β-Spline functions and widely used in the literature and scientific research. Overall, the high quality of the database was detected as the most important driver for modelling with algorithms almost equivalent each other. The use of a non-destructive sampling method allowed the full measurement of all the trees necessary to build a mathematical function properly. The results clearly highlight the ability of all the tested models to reach a high statistical significance with an adjusted-R squared higher than 0.9. A very low mean relative absolute error was also calculated with a cross validation procedure and small standard deviation were associated. Substantial differences were detected with the TapeR prediction. Indeed, the use of mixed models improved the data handling with outputs not affected by autocorrelation which is one of the main issues when measuring trees profile. The profile data violate one of the basic assumptions of modelling: the independence of sampled units (i.e., autocorrelation of measured values across the stem of a tree). Consequently, the use of simple parametric equations can only be a temporary resource before more complex built-in apps are able to allow basic users to exploit more powerful modelling techniques.Keywords
Funding Information
- European Commission (LIFE13 BIO/IT/000282)
This publication has 35 references indexed in Scilit:
- Natural forest expansion into suburban countryside: Gained ground for a green infrastructure?Urban Forestry & Urban Greening, 2013
- Selecting pseudo‐absences for species distribution models: how, where and how many?Methods in Ecology and Evolution, 2012
- Addressing climate change in the forest vegetation simulator to assess impacts on landscape forest dynamicsForest Ecology and Management, 2010
- Forest management and carbon sequestration in wood productsEuropean Journal of Forest Research, 2009
- A comparison of four process-based models and a statistical regression model to predict growth of Eucalyptus globulus plantationsEcological Modelling, 2009
- Problems of using pines in Tuber melanosporum culture: soils and truffle harvest associated with Pinus nigra and P. sylvestrisAgroforestry Systems, 2007
- Comparison of modelled and monitored deposition fluxes of sulphur and nitrogen to ICP-forest sites in EuropeBiogeosciences (online), 2006
- Structure and growth of a small group selection forest of calabrian pine in Southern Italy: A hypothesis for continuous cover forestry based on traditional silvicultureForest Ecology and Management, 2006
- The significance of different indices for stand structure and diversity in forestsForest Ecology and Management, 2001
- Timber quality after thinning from above and below in stands of Pinus sylvestrisScandinavian Journal of Forest Research, 1996