Effects of stand parameters on conifer regeneration success in pine shelterwood stands in Estonia

Shelterwood method is indispensable in many forests where common clearcuts are excluded due to nature conservation, recreational use, or need for special management. We evaluated the impacts of light conditions, site fertility, cutting intensity, and soil scarification on the natural conifer regeneration density and height growth in Scots pine (Pinus sylvestris L.) stands managed by shelterwood cutting. The aim of the study was to reveal functionally important site parameters in the shelterwood system that affects conifer regeneration most strongly in hemiboreal forest. In general, the number of shelter trees decreased conifer regeneration height increment and success index (density x mean height/time since initial cutting). After the first cut, the optimal amount of first storey shelter trees was around 200 trees ha(-1), or half of the basal area of the normal stand. Soil scarification increased and higher proportion of deciduous regeneration decreased density-related parameters (density and success index) of conifer regeneration. The positive effect of scarification was pronounced on poor soils, where density increase was fivefold. The conifer regeneration characteristics were not affected by soil properties, except soil phosphorus, which was positively correlated with seedlings' height growth. Site fertility increased height increment and success index after the second cut, when regenerated trees are larger. Although shelterwood cutting is commonly applied in less productive forest types in boreal and hemiboreal pine forests, this regeneration method can be just as successful also in fertile sites.