Site factors as multivariate predictors of the success of natural regeneration in Scots pine forests

Site factors, such as regional climate (temperature, humidity, frost and radiation) and ground conditions (topography, soil and water properties and vegetation) were measured in sample plots in 26 naturally regenerated Scots pine-dominated stands in southern Sweden. The data were employed to develop multivariate prediction models for assessing the suitability of particular sites for natural regeneration with seed trees. The suitability for natural regeneration was estimated as the number of established coniferous stems at normal precommercial thinning age. Cross validated Partial Least Squares (PLS) regression models with different types of independent variables were developed. The models revealed strong climatic correlation with regeneration the main variation in which can be expressed in terms of latitude and altitude, e.g. positive correlations with temperature Sum, length of growing season and humidity, and negative correlation with frost frequency. The best model explained 94% of the variation in number of established stems in the stands. (C) 1998 Elsevier Science B.V.