Soil properties, labile pools of soil organic carbon and their variations under broadleaf and coniferous plantation in Hyrcanian forest, northern Iran

Afforestation, as a tool to mitigate carbon emission is constrained by available land areain several countries, but Iran has the potential of plantation. In doing so, differences in soilstocks between tree species could give an indication of the effects of future managementchanges. Hence, a better understanding of tree species traits on soil properties is required topredict how changes in ecosystems occur with tree species composition. This studyinvestigated the effect of selected tree species on soil properties, carbon sequestrationpotential of tree species across soil profiles (0-200 cm) and evaluated the tree specieseffects on labile soil organic carbon pools to introduce a unique soil quality indicator. Thestudy site was Shalman Research Station in the Hyrcanian forests, northern Iran. Our resultsshowed significant alterations in soil properties by tree species with the greatest changes inthe top soil layer. The greatest cation exchange capacity (CEC) difference (Δ 4.17) wasfound between A. glutinosa and J. polycarpos in 0-20 cm. The greatest differences (Δ 2.58)in mean weight diameter (MWD) of soil layers were found in the top soil layer between A.glutinosa and T. distichum. All species produced also a higher N and organic carbonconcentration in the top soil layer (0-20 cm) in the following order: A. glutinosa > Q.castaneifolia > P. caspica > J. polycarpos > T. distichum > P. taeda. The varied amount oftotal soil organic carbon stocks was greater under Alder (A. glutinosa) and Oak (Q.castaneifolia) than other tree species with 206.24 and 195.26 (Mg.ha-1), respectively; and P.taeda had the lowest amount (136.94 Mg ha-1) across the soil profile. For all labile pools,A. glutinosa and T. distichum had the highest and the lowest percent of labile organiccarbon, respectively. Consequently, the Cmin in the range of 10.11-14.04% and microbialbiomass carbon in the range of 1.05-1.66% shared the highest and lowest proportion of soilorganic carbon across 0-200 cm depth, respectively. We concluded that broadleaf trees hadgreat potential for carbon sequestration across soil depth and among them; alder had higheffect on soil properties and soil organic matter.