Question: What is the spatial relationship between remaining trees and the establishment and development of recruited saplings?
Location: The Pinus sylvestris forest Pinar de Valsaín, in the Sistema mountain range (central Spain).
Methods: Three 0.5 ha plots have been analysed. The saplings were located in a 2 m × 2 m grid, characterizing their spatial pattern through a nested ANOVA. The spatial pattern of stems was analysed using the L(d) function. To analyse the spatial relationship between stems belonging to different cohorts, the intertype Lrs(d) function was used. Finally a new function Krx(d) is presented as a method to analyse the relationship between the spatial distribution of stems and the sapling density (a sampled continuous variable).
Results: The mother trees show cluster pattern at scales of ca. 12 m - 22 m, leading to a spatial pattern at 14 m - 16 m for the saplings during the regeneration period. At the beginning of the shelter phase, saplings less than 1.30 m in height show spatial repulsion from the old crop at distances above 10 m, whereas taller saplings show repulsion at shorter distances, due to the suppression of sapling development near the mother trees. At the end of the regeneration period, saplings < 1.30 m appear under the last remaining mother tree canopies.
Conclusions: In the stands analysed, located at the southern limit of Pinus sylvestris distribution, this species behaves as half-shade tolerant. This study shows that the Krx(d) function might be widely applied to analyse the relationship between patterns that occur at different scales or between a point pattern and a continuous variable, being a useful tool for analysing some forest processes.