Comparison of community structure and soil characteristics in different aged Pinus sylvestris plantations and a natural pine forest

Abstract

The objective was to determine the change in ecosystem characteristics in terms of time passed after replanting with Pinus sylvestris, and to compare this with a natural forest. Five P. sylvestris stands of each age group: 2–3, 10–12, 40 and 80 years old, were selected and other five in the natural pine forest in Lillo (León, NW Spain) were sampled. The dimensions of the pines (height, perimeter and mean crown diameter), their density (estimated from middle distance), characteristics of the understory (cover and richness of both herbaceous and woody species) and soil (pH, organic matter, total nitrogen and available nutrient content) were studied at each stand. No differences were observed in the dimensions of the pines in the 40- and 80-year-old stands, although the crown diameter and mean trunk perimeter were larger in the natural forest. The coefficient of variation of these variables was significantly larger in the natural forest, indicating greater variability in the age of the pine trees and making more heterogeneous conditions. Spatial distribution of the pines presented an aggregated pattern at most stands in the natural pine forest, whilst it was random in the 40- and 80-year-old plantations and uniform in the most recent ones. There was no clear trend in terms of age in the understory characteristics, with the 10-year-old plantation differing the most due to its lower herb and higher woody species cover. With regards the soil, the natural forest has a lower pH and higher organic matter and phosphorus content, whilst the 2–3- and 10–12-year-old plantations were generally associated with a higher K content. The CCA carried out for global comparison of all the results showed separation between the two most recently planted groups and the mature ones, more similar to the natural forest. The complex gradient represented by the first two axes of the CCA presented a significant correlation with the characteristics of the trees and some of the understory, like herb richness and total species richness.