Density and population structure of the natural regeneration of Scots pine (Pinus sylvestris L.) in the High Ebro Basin (Northern Spain)

Abstract

This paper presents the analysis of 11 natural regenerated stands in native Scots pine forests located in the High Ebro Basin (Northern Spain). The natural regeneration showed a continuous age distribution, early height differentiation and a high stability in the height position of seedlings. Total density and main crop (trees selected for future commercial harvest) density models were developed to study the relationship between natural regeneration and site variables. Soil sand content was an important ecological factor distinguishing two groups of plots. Hardwood and Ericaceae species competition were the main factors that explained total density but only in soils with low sand content. Intensive herbivore grazing was proposed to produce a strong reduction of viable seedlings. Thus, vegetation-control treatments and limitation of cattle grazing in regeneration areas are highly recommended in the native Scots pine forests of the High Ebro Basin.