Abstract
Sustainable production of wood is one of the main services provided by forest systems. Site productivity in the case of forests is often evaluated through the site quality. However, most of the works addressing the site quality have been done at local or regional scale. In this work, we aim to develop site quality models for five dominant species in Spanish forests (Fagus sylvatica, Pinus pinaster atlantica, Quercus pyrenaica, Pinus nigra, Pinus sylvestris) and create site quality maps at a national-scale from these models. First, we develop site quality models using site form (height-diameter relationship) as the reference index and the Spanish National Forest Inventory as dataset. Then, we fit spatial additive models entering physiographic and climatic variables in order to predict the site quality over the whole country. Additionally, we plot site form maps for the five species in order to describe spatial pattern in site quality at a national scale. Altitude and aspect appeared to be fundamental variables in the assessment of site quality. The accuracy of the spatial additive models ranged from 38.2% to 47.9%. The correspondence between the predicted and observed maps of site qualities is clear. Our results provide a tool which could be used by forest managers in land use planning as well as in forest policy decision-making at a national scale. We suggest that this method could be used in other countries and that the maps could be expanded to the European scale to assessing the way in which site quality varies across Europe always considering that the relationships between forest productivity and environmental variables could vary among biogeoclimatic zones.
Highlights
Site quality has long been used in forestry as a proxy of site productivity
We selected five species widely distributed in Spain and which form genuine, monodominant forest according to the European Forest Type (EFT) classification (Barbati et al, 2014, 2007b): Pinus pinaster Ait. ssp atlantica (P. pinaster, hereafter), Fagus sylvatica L., Quercus pyrenaica Willd., Pinus nigra Arn. and Pinus sylvestris L. (Table 1)
Hossfeld II model (H-II) was the model selected for all the EFTs with the exception of P. nigra, for which Bertalanffy-Richards model (B-R) was selected
Summary
Site quality has long been used in forestry as a proxy of site productivity. This variable is of interest for predicting growth and yield of forest stands (Álvarez-González et al, 2005; Clutter et al, 1983; Diéguez-Aranda et al, 2005) and for studies on ecological diversity (Franklin et al, 1989), forest structure (Larson et al, 2008) and forest disturbances (Wei et al, 2003) among others. Site quality has traditionally been expressed as the relationship between dominant height and age (site index) for even aged forests. Site form can be useful to determine the site quality of even-aged stands where the age is unknown, as occurs in the National Forest Inventories (NFIs) of some countries (Tomppo et al, 2010).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
