Development and renewal-conditions of dune pine forests second growth in the lichen and cowberry site type in Southwest Estonia

Edela-Eesti luitemetsade järelkasvu arengust ning uuenemistingimustest sambliku ja pohla kasvukohatüübis On the southwestern coast of Estonia dune pine forest covers approximately 3000 hectares. This area includes coastal pine forests. The dune pine forest natural renewal in Southwest Estonia is the object of research. The natural regeneration of Scots pine (Pinus sylvestris L.) at the cowberry site type and at the lichen site type are observed. The necessary observations were made and primary data were collected in 1999-2006 from 28 sample plots, wherefrom 16 were situated at the lichen and 12 at the cowberry site type. The aim of the present study was to find out how old stand and forest site type influences the growth of second growth (height, height increment, age and number of trees per unit area) and its morphological parameters (length of needles and shoots and their dry mass). Development and renewal-conditions of dune pine forests second growth in the lichen and cowberry site type in Southwest Estonia Ecological dependences of Scots pine second growth in Southwest Estonian coastal pine forests in most common Vaccinium vitis-idaea and Cladina site types were explained. In these 120-190 year old coastal stands, the structure of stand upper layer and formation factors, appearance and condition of second growth and its dependence on old stand density were investigated. During the past decades these stands have been tried to renew by gradual thinning, which in some part has given some positive results. At this moment, in Vaccinium vitis-idaea pine forests, there is growing on an average 2661 and in Cladina pine forests 2556 second growth's pine, which height is from some centimetres to 10 meters and more than 85% of these trees are totally viable. Investigation results revealed, that there is a number of various factors, that influence formation and growth of Scots pine natural regeneration, wherefrom the most important is old stand's density, which reveals itself by light conditions and root competition. From investigation results may conclude: • In the Cladina site type, density in the range 0,45-0,88 affects second growth's increment of height on an average (r = -0,76). In the Vaccinium vitis-idaea site type density affects second growth's increment of height mildly (r = -0,45). Increment of height of natural regeneration increases when old stand's density decreases. • In the Cladina site type, density influences Scots pine second growth's morphological parameters of shoots and needles significantly more than in the Vaccinium vitis-idaea site type. Poorer growth and less productive soil conditions of Cladina site type compared to Vaccinium vitis-idaea site type appeared in smaller increment of height of second growth trees, in smaller length and dry mass of shoots and needles, but in greater density of needles. The conclusion drawn from different comparisons was that narrow clear-cuts have great influence on the natural regeneration's growth and number at the Cladina site type. When we sought connections between the old stand density, taking into consideration also narrow clear-cut sample areas with second growth's number of trees, height and increment of height, the connections were significantly stronger. In these areas the number of trees and second growth's increment of height were considerably higher than in the sample plots, which were under old stand's shelter (14, 15 and 27). Clear-cut strips up to 30 m in width with no old forest's direct shelter and root competition to second growth create favourable site conditions for natural regeneration. Earlier attention has been drawn to the favourable effect of clear-cut strips on the natural regeneration of heath pine forests. Pine forests with 25 m clear-cut strips have naturally regenerated well in Sagadi and Märjamaa forest districts (Etverk, 2000).