Effect of thermal conditions and precipitation on growth rate of Scots pine

The aim of the experiment presented in this paper is to assess the relationship between the height and diameter increase rate and the thermal conditions and precipitation during its growth. The experiment was carried out in the Agro- and Hydrometeorology Observatory of the Wrocław University of Environmental and Life Sciences in 2013–2015. The height and diameter measurement was made each time on the same 43 plants, randomly selected at the stage of setting up the experiment in 2012 and specially marked. Plants included in further analyses were divided into 5 classes and the classification criterion was their height in the 3rd year of cultivation. Initially, an analysis of relationships of selected morphological parameters of Scots pine was carried out, i.e. of the heights and diameters against the changing weather conditions, i.e. precipitations and air temperatures. Subsequently, an effect of the thermal conditions and the amount of precipitation on growth of Scots pine was assessed with the use of the two meteorological parameters mentioned above. These parameters were used as their accumulated sums, calculated as of the dates of biometric measurements, made at the end of each month (the last ten days of a month) in the summer half-year period. Multiple regression analysis was applied to evaluate the effect of thermal conditions and precipitation on the growth of Scots pine in both variants and the significance of the relationships under study was examined with the use of an adjusted coefficient of determination R2. The analyses and calculations indicate a close significant relationship between the height of pine trees and their diameter at the base on any measurement date. Analyses of different measurement periods indicated a decrease in significance of the relationships between the height of pine trees and their diameter at the base. A decrease in these relationships is becoming more and more pronounced with the age of the trees. Of the two weather parameters, i.e. total air temperature and total precipitation, the precipitation dominates in the relationship with the trees height and air temperature – with the trees diameter.