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

Document Type: Research Paper

Authors

1 Zanjan University, Zanjan, Iran

2 Agricultural and Natural Resources Research and Education center of Guilan, AREO, Rasht, Iran

Abstract

Afforestation, as a tool to mitigate carbon emission is constrained by available land area
in several countries, but Iran has the potential of plantation. In doing so, differences in soil
stocks between tree species could give an indication of the effects of future management
changes. Hence, a better understanding of tree species traits on soil properties is required to
predict how changes in ecosystems occur with tree species composition. This study
investigated the effect of selected tree species on soil properties, carbon sequestration
potential of tree species across soil profiles (0-200 cm) and evaluated the tree species
effects on labile soil organic carbon pools to introduce a unique soil quality indicator. The
study site was Shalman Research Station in the Hyrcanian forests, northern Iran. Our results
showed significant alterations in soil properties by tree species with the greatest changes in
the top soil layer. The greatest cation exchange capacity (CEC) difference (Δ 4.17) was
found 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 carbon
concentration 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 of
total 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 organic
carbon, respectively. Consequently, the Cmin in the range of 10.11-14.04% and microbial
biomass carbon in the range of 1.05-1.66% shared the highest and lowest proportion of soil
organic carbon across 0-200 cm depth, respectively. We concluded that broadleaf trees had
great potential for carbon sequestration across soil depth and among them; alder had high
effect on soil properties and soil organic matter.

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