National scale variability in forest stand variables among regions of provenances in Spain

Abstract

An in-depth characterization of the forests of 10 dominant species by stand variables at national scale showed, that overall, stands growing in the southernmost regions of Spain display low regeneration. Otherwise, the relationships between stand variables and geographic location are species dependent. Similarly, the degree of inter and interregional variability varies strongly among species. The regions of provenance can potentially be used as units with uniform ecological, phenotypic, and genetic traits to characterize forests. Our objective was to characterize forests through stand variables at national scale for the 10 most widespread dominant tree species in Spain (five Pinaceae and five Fagaceae species) using the regions of provenance as ecologically homogeneous areas. We used the National Forest Inventory as the dataset and multivariate analyses of variance with a bootstrapping and principal coordinates analysis for the statistical evaluation. Overall, the mean diameter of adult trees was negatively related to recruitment variables, and the mean height of adult trees was negatively related to shrub coverage and number of shrub species. The statistical analyses revealed significant differences between regions of provenance for all variables. The regions of provenance where Pinus sylvestris, P. nigra, P. pinea, Quercus suber, and Q. ilex are dominant, displayed a large variability among regions. In contrast, the regions of provenance for P. halepensis, Q. pyrenaica, and Q. faginea displayed a small low inter-regional variability. Forest management as well as climate conditions shaped deeply forests, which lead to differences on stand variables among provenances by species. Stands growing on the southernmost locations, overall, are more prone to the forecasted climate change due to the low rates of regeneration.