Growth and Yield Models for Balsa Wood Plantations in the Coastal Lowlands of Ecuador

Abstract

Balsa trees are native to neotropical forests and frequently grow on fallow, degraded land. Balsa can be used for economic and ecological rehabilitation of farmland with the aim of restoring native forest ecosystems. Although Ecuador is the world’s largest producer of balsa, there is a lack of knowledge about production indicators for management of balsa stands in the country. The aim of this study was to develop growth and yield models (i.e., site index (SI) curves and stem volume models) for balsa plantations in the coastal lowlands of Ecuador. Balsa trees growing in 2161 plots in seven provinces were sampled. Here we present the first growth and yield models for the native, although underutilized, balsa tree. Three curve models were fitted to determine SI for balsa stands, differentiating five site quality classes. Eight volume models were compared to identify the best fit model for balsa stands. The mean annual increment was used to assess balsa production. The generalized algebraic difference approach (GADA) equation yielded one of the best results for the height–age and diameter–age models. The Newnham model was the best volume model for balsa in this comparative study. The maximum annual increment (i.e., for the best stand index) was reached in the second year of plantation. The fitted models can be used to support management decisions regarding balsa plantations. However, the models are preliminary and must be validated with independent samples. Nevertheless, the very fast development of the native balsa tree is particularly promising and should attract more attention from forest owners and politicians.

Improving the Modeling of the Height–Diameter Relationship of Tree Species with High Growth Variability: Robust Regression Analysis of Ochroma pyramidale (Balsa-Tree)

“…According to the site-index results for O. pyramidale evaluated in Approach 1, the Chapman-Richards model was the most representative for h dom predicted, although it showed a slight tendency to underestimate at the lowest heights and overestimate at the highest (Figure 4a). Because it is a non-linear biological model with three parameters, it is very flexible and can properly represent the growth of an allometric variable like h dom over time [5,39,41].…”

“…Since the site-index curves from Figure 4b do not include all observations, our site-index classification, pertaining to intervals upper-class I and lower-class III, may have been 'kept open'-as described by Cañadas-López et al [5].…”

“…The effects of site-index on height-diameter relationship were only assessed for the fit data-set; namely, site-index was only used to assess model fit and not validation. precipitation, average annual temperature around 25 • C and average annual air humidity of about 85%, with slightly uneven topography and soils composed mainly of silt and clay and pH around 6.5-7.0 [5,27].…”

Stem volume equation for constructing local volume table of Pinus merkusii Jungh et de Vriese in Tana Toraja community forest

“…Selection of the best model is carried out by calculating the value of the coefficient of determination (R 2 ), coefficient of determination adjust (R 2 adj. ), t-test, root means square error (RMSE), mean deviation (MD), and mean absolute deviation (MAD) (Xia et al, 2013;Gonzalez-Benecke et al, 2014;Lee et al, 2017;Cañadas-López et al, 2019;Hernández et al, 2019;Maltamo et al, 2019;Saarinen et al, 2019;Brūmelis et al, 2020;Marzulli et al, 2020;Socha et al, 2020). This value is calculated as follows, using equations 10 to 15:…”

Research on the feasibility of polyethylene terephthalate foam used in wind turbine blades

“…The core material properties concerned with wind turbines are tensile, compression, shear, and peel. The sandwich core materials should meet the following characteristics: (1) mechanical properties should meet the requirements of wind turbine blade design parameters; (2) small specific gravity; (3) fantastic temperature resistance; (4) excellent chemical corrosion resistance; (5) outstanding compatibility with infusion resin; (6) low cost; and (7) environmentally friendly. 5 Wind turbine blades are made of sandwich composite structures in which the core materials are combined with glass fiber and resin.…”