Developing a dynamic growth model for maritime pine in Asturias (NW Spain): comparison with nearby regions

Abstract

Abstract• Key message A dynamic growth model was developed for maritime pine in Asturias. During the evaluation process, a stand volume ratio function proved the best of two alternative methods for estimating merchantable volume. Comparison of the developed model with existing models for nearby regions showed that a single • Context Maritime pine is one of the most important tree species in NW Spain. There was no existing dynamic growth model for this species in Asturias.• Aims To develop a dynamic growth model for maritime pine in Asturias, by evaluating two different methods of estimating volume (a disaggregation system and a stand volume ratio function), and to compare the developed model with existing models for Galicia and northern Portugal are the goals of this study.• Methods The dynamic model is based on the state-space approach, in which three state variables characterize the stand at any point in time: dominant height, number of stems per hectare and stand basal area. The transition function for the first variable was developed on the basis of stem analysis data in a previous study, while the corresponding functions for the last two variables were simultaneously fitted with data obtained from successive measurements of permanent plots. An appendix outlining the implementation of a stand growth simulator in the R environment is included to facilitate model use and evaluation.• Results When the whole model was used to project the stand conditions, the stand volume ratio function performed best, yielding a root mean square error of 22.4 m 3 ha −1 and a critical error of 18.4 %. Comparison with models developed for other regions revealed both similarities and differences, some of which may be attributed to an unequal distribution of the available data in age and site quality classes.• Conclusion The proposed dynamic growth model provided accurate results, and comparison with other region-specific models showed that a single dynamic model may suffice for the whole of the NW Iberian Peninsula.

Use of depth-first search and direct search methods to optimize even-aged stand management: a case study involving maritime pine in Asturias (northwest Spain)

“…A detailed explanation of the data and methods used to develop this model can be found in Arias-Rodil et al (2015). The model is based on three state variables (dominant height, H, calculated as the average height of the 100 thickest trees per hectare; number of stems per hectare, N; and stand basal area, G), which can be projected with the corresponding transition functions (eqs.…”

“…(4), which yields 16 different initial stands. The values of S and N were established according to the observed ranges for maritime pine in Asturias (Álvarez-Álvarez et al 2011;Arias-Rodil et al 2015).…”

“…Such a difference would be important for forest practitioners when implementing stand-level optimization. In a previous study, Arias-Rodil et al (2015) also compared these two alternative methods in total volume estimation and found the stand volume ratio function to be slightly more accurate. We therefore used the stand volume ratio function for the remaining optimization procedures.…”

“…The dynamic growth model used in this study (Arias-Rodil et al 2015) was developed on the basis of data obtained in stands younger than 65 years. Projections beyond this range were reasonable (Arias-Rodil et al 2015), and the model was therefore used for stand-level optimization.…”

“…However, this does not guarantee maximum profitability, as maximizing the production of pulpwood may be preferred if the price is not too low. To provide an objective evaluation of management schedules (usually defined by a set of partial cuttings -thinnings-and the rotation length, e.g., Miina 1996;Pukkala et al 2014a), Arias-Rodil et al (2015) have recently developed a dynamic stand growth model for maritime pine in Asturias. This model provides useful information for the decision making process (Pasalodos-Tato and Pukkala 2007;Pasalodos-Tato et al 2009).…”