Spatial interactions between Scots pine (Pinus sylvestris L.), common oak (Quercus robur L.) and silver birch (Betula pendula Roth.) as investigated in stratified stands in mesotrophic site conditions

Two stratified stands have been examined in the sample plots comprising an area of 2.04 ha. The age of the older-generation trees ranged from 115 to 135 years, and the younger-generation trees from 20 to 60 years. As has been shown by spatial analyses, young pines tend to concentrate in the vicinity of old individuals, and birches tend to fill gaps. Oaks have different spatial patterns in each of the stands. In one, oaks frequently grow close to old pines and birches, avoid gaps and emerge more frequently in the vicinity of larger trees; in the other, oaks occur at random and tend to avoid the neighbourhood of old pines. The following conclusions have been made: (i) pine, after successful regeneration, is able to maintain or even increase its partition in the species composition of stands in the subsequent development stages; (ii) pine is less sensitive to the competition of the upper story than birch and oak; (iii) the upper story controls competitive interactions between pine and birch; (iv) competition between forest floor vegetation and seedlings may play a key role in the frequently observed transition of mixed oak-pine forests into the forest dominated by oak. (C) 2004 Elsevier B.V. All rights reserved.