Effect of Different Tree Plantations on the Chemical Properties and Microbial Activity in Galician Forests Soils

Forest soils are crucial carbon sinks, with the soil microbial community playing a key role in the stabilization of organic matter and harboring numerous ecosystems services. These ecosystems can be affected, among other factors, by the different tree species present in the forest canopy. This study is focused on forests soils located in Galicia (on the north-west of Spain). Different soil properties and microbial activity were analyzed in 54 forest plantations, with different plant covers: birch, chestnut, eucalyptus, walnut, pines, oak and shrublands. These forest soils have in general an acid pH and a high organic matter content, but a small amount of phosphorus. These properties are mainly related to the parent material and the overall climatic conditions of this region, namely the high rainfall scores. The soil under eucalyptus and birch plantations were the driest (13% and 14% on average respectively) vs. the moistest with 27% on average under shrublands. The results regarding microbial activity showed that soils under walnuts have the biggest respiration rates whereas the smallest were under eucalyptus but there were no differences regarding the β-glucosidase enzyme activity. These results show that the forest management, specifically, which tree species are cultivated, has an impact on the soil microbial respiration and should be considered when elaborating forestry exploitation plans, especially in the current scenario of climate change where the C amount that healthy forest soils will be able to fix become crucial.