Biomass growth simulations in a natural mixed forest stand under different thinning intensities by 3-PG process-based model

摘要

This work intends to check the efficiency of the 3-PG model (Physiological Principles in Predicting Growth) (Landsberg and Waring in For Ecol Manag 95:209-228, 1997) in the simulation of biomass growth for a natural Mediterranean maritime pine forest with two canopy layers comprising different species (Pinus pinaster Ait. subsp. mesogeensis and Quercus ilex L. subsp. ballota) in the Cuenca Mountains, Spain, that had previously been subject to thinning. We assigned a dominant (P. pinaster Ait.) and a subdominant (Quercus ilex L.) component, individually parameterised. The competition between dominant and subdominant layers was simulated with specific modifications to the input solar radiation, precipitation, evapotranspiration and available soil water without any structural change to the model. Data from three study sites were used: control (C, no thinning over 30 years), treatment 1 (T1, light thinning, with thinning operations carried out in January 2004) and treatment 2 (T2, moderate thinning, with thinning operations carried out in January 2002). The data were divided into two sets: (1) A model data set from C site was used to parameterise 3-PG, and (2) an independent testing data set from the T1 and T2 sites was used to test growth predictions made by 3-PG. We report successful outcome its parameterisation, obtaining accurate predictions compared to the long-term field measurements acquired from thinned stands. Results show that the current implementation of the 3-PG slightly over- and underestimated biomass components for both pine and oak after thinning. However, values for the coefficient of efficiency (EC) were very high for both species (0.85-0.99). According to the results, the 3-PG may provide a feasible tool for estimating biomass growth and guiding forest management in natural Mediterranean maritime pine forest stands.