Environ Exp Biol (2017) 15: 275–282

Tree regeneration in noble broadleaved tree stands at their northern limit: implications for conservation management

Abstract

In Latvia, the noble broad-leaved tree species woodland with pedunculate oak (Quercus robur L.), small-leaved lime (Tilia cordata Mill.), Norway maple (Acer platanoides L.), wych elm (Ulmus glabra Huds.), white elm (Ulmus laevis Pall.) and common ash (Fraxinus excelsior L.) has decreased to about 1% due to the historical legacy of wood extraction and conversion of fertile soil to agricultural land-use. The aim of the current study was to determine the tree age structure in the canopy and size structure in the shrub layer of broad-leaved tree stands to determine past changes and to predict future trends in tree species composition in the context of potential management methods. In 50 randomly selected broad-leaved tree stands, plots of size 0.1 ha were established. In the plots, diameter at breast height was measured for all trees with diameter >10 cm and cores were removed from all of these trees. All other stems were counted by species in height classes ≤ 1 m, 1.1 to 5 m, 5 to 10 m. The stands were classified into 10 groups based on canopy composition in age classes. Norway spruce [Picea abies (L.) H. Karst.] was common in various tree layers of in many of the groups, and it is recommended that it should be removed during stand tending. Q. robur regeneration should be promoted in specific cases where abundant in the < 1 m layer and where large gaps can be created. T. cordata is commonly present in several tree layers and its growth could be promoted by thinning of P. abies where present. Abundant Q. robur regeneration is sometimes found in Scots pine (Pinus sylvestris L.) stands.