Scots Pine Seedlings Growth Under Different Ca/Mn Soil Ratios

Low Ca/Mn ratios in soils are considered one of the causes of forest decline in the northern hemisphere, in particular, Scots pine forest decline. Nevertheless, there are little data on the growth and development of forest trees, especially Scots pine, under different soil concentrations of calcium and manganese. Therefore, the present study aims to estimate Scots pine seedlings' height growth under different Ca/Mn soil ratios. For this purpose, we measured the height of 8-month-old Scots pine seedlings that grew on two adjacent plots, whose soils had different origins and, therefore, differed significantly in their properties. Some of these soil properties, namely exchangeable and hydrolytic acidity, the sum of absorbed bases, the content of humus, alkali-hydrolyzable nitrogen, exchangeable potassium and calcium, mobile sulfur and phosphorus, mobile compounds of copper, zinc, cobalt, cadmium, lead, and manganese, were determined by various methods. Pairwise comparison of values of listed above properties of soils from these experimental plots revealed that these soils differed significantly in manganese and calcium content and acid-basic properties. Therefore, as the ratio of molal concentrations of exchangeable calcium to manganese mobile compounds (Ca/Mn ratio) in the soil is a parameter that combines those soil properties that differed significantly between the two plots, we used the one-way ANOVA to verify the association between Ca/Mn ratio and Scots pine seedlings' height growth rate. As a result, this analysis revealed a statistically significant difference (p < 0.05) in mean height between Scots pine seedlings that grew under relatively low (45.28/1) and relatively high Ca/Mn ratio (195.12/1) in soil. Nevertheless, although the mean height of Scots pine seedlings that grew at the ratio of 45.28/1 was approximately 1.6 times lower than seedlings that grew at the ratio of 195.12/1, the optimum value of the Ca/Mn ratio in the soil for Scots pine remains unknown. In addition, the hypothesis that untested soil properties have also caused the differences in the mean height of seedlings was not rejected. Thus, the impact of the Ca/Mn ratio together with the potential impact of untested soil properties on the growth and development of Scots pine and the optimum value of this ratio for this species needs to be investigated in further studies.