Functional diversity of soil microbial communities in boreal and temperate Scots pine forests

Scots pine (Pinus sylvestris L.) is one of the most widespread conifer species in Europe, able to tolerate a wide variety of climatic conditions. The aim of the study was to compare the activity, functional diversity and community-level physiological profiles (CLPPs) of soil microorganisms in Scots pine forests of the boreal and temperate climatic zones. The soil samples were taken from the O and A soil horizons in northern Finland (boreal pine forest, BP) and Poland (dry and mesic temperate pine forest, TDP and TMP, respectively) and measured for water-holding capacity, pH, organic C, dissolved organic C (DOC) and the total contents of N, P, Ca, Mg, K, Na and Mn. The microbial activity (multiple substrate-induced respiration rate) and functional diversification (community-level physiological profiles, CLPPs) were assessed using the MicroResp (TM) system with 22 different C substrates. The BP soils were finer textured and contained more Ca, K, Mg, Mn and Na but less N and P than the soils under the temperate forests. The pH values did not differ between the studied forests. The studied pine forests did not differ in the measured microbial properties in the O horizon. However, in the A horizon, the microorganisms from the BP soil were less active and less functionally diverse than those from the temperate forest soils. The CLPPs of the BP soils differed from those of the temperate forest soils, wherein the largest difference was from the use of carboxylic acids and amino acids. The microorganisms from the BP soils used carboxylic acids more efficiently but were much less efficient in decomposing amino acids than those from the temperate forest soils. These differences were related to the contents of DOC, N and P which are influenced by climate and bedrock properties. Our results indicate that soil microbial properties in the O horizon depend mainly on the vegetation, whereas in deeper layers, they depend to a larger extent on bedrock properties and climatic conditions.