Taper Function for Pinus nigra in Central Italy: Is a More Complex Computational System Required?

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.

Analysis of Taper Functions for Larix olgensis Using Mixed Models and TLS

“…Another innovation of this study is that TLS was entirely used to obtain the diameters, and TH was used to establish a taper equation mixed model, which was obtained without cutting down trees. The RD1000 was also adopted for non-destructive tree measurement, as it had the largest mutation when the relative height was 0.64-0.8, similar to the results of our previous study (RH75) [37]. Sun et al [32] used a modified Schumacher equation to fit the Populus L. taper equation of the TLS, which yielded a fitting R 2 = 0.96, which is similar to that of the basic model in our study but lower than that of the mixed model (R 2 = 0.98).…”

Effect of Thinning on Forest Scenic Beauty in a Black Pine Forest in Central Italy

“…stands in Italy cover an area of 236,467 ha, corresponding to 2.5% of the total forest area. In Tuscany, the area covered by black pine forests is 20,500 ha with an average stand age of approximately 60 years [56,57].…”

Forest Stand Management and Biomass Growth

“…The contribution to the Special Issue comprises 19 articles by authors involved in university, research institutions, and agencies, from nine countries from Asia, Europe, and America. The articles deal with agroforestry [1], natural forests [2][3][4][5][6][7][8][9][10][11][12], and forest plantations [13][14][15][16][17][18][19].…”

“…Hook. [4,16], Pinus sylvestris L. [10,15], Pinus taeda L. [14], Pinus nigra J.F.Arnold [18], Pinus rigida Mill. and the understory Quercus variabilis Blume, Quercus acutissima Carruth., Quercus mongolica Fisch.…”

“…Tree growth dynamics and environmental factors explored along the Italian latitudinal gradient are illustrated in [11] for a 5-year monitoring time in beech forests. The article [18] on the taper function for Pinus nigra from Central Italy can be conveniently used to develop estimation procedures of stem profile for assortment evaluation useful in the wood products supply chain. The study [19] demonstrates the important contribution of naturally regenerated understory tree biomass to total biomass in pine plantations and explains that the biomass growth characteristics of understory vegetation can vary greatly with dominant species; therefore, care should be taken when adopting allometric equations developed elsewhere and for larger trees.…”