Site index estimation in Scots pine (Pinus sylvestris L.) stands in the High Ebro Basin (northern Spain) using soil attributes

Site index curves and an edaphic discriminant rule for Scots pine stands in the High Ebro Basin (northern Spain) are presented to estimate site index under different silvicultural situations. High-grading practices strongly m odify the forestry structure by the means of bias in the dominant height an d stand density. In order to achieve the silvicultural and site variability of Scots pine stands in the studied area, 75 plots from the National Fores t Inventory of Spain (NFI) were selected. In these plots 46 dominant trees were cut down and 104 trees were bored at stump and at breast height (1.3 m ). In each plot a soil sample from the first 10 cm of soil was taken and si gns of dimensional cutting were recorded. Site index curves and the edaphic discriminant rule were developed. The site index curve model used is an ex tension of the Richards model. The site factors selected in the discriminan t rule represent the most important edaphic parameters for forest productiv ity (texture and the assimilability of the nutrients). Site quality of the studied stands was medium-low as compared with other site index curves for Scots pine around the world. The edaphic discriminant rule presented is use ful for estimating site index classes in stands exposed to dimensional cutt ing and in young stands of Scots pine in the the High Ebro Basin (northern Spain). Site index curves were fitted to allow an estimate of the site inde x of undisturbed and stands which were not high-graded.