Dynamics of humus forms and soil characteristics along a forest altitudinal gradient in Hyrcanian forest

Altitudinal gradients significantly influence humus form distribution and soil properties in Hyrcanian forests, with distinct mechanisms at play. While soil characteristics such as temperature, pH, calcium carbonate content, nitrogen levels, carbon-to-nitrogen ratio, and microbial biomass nitrogen show strong correlations with altitude, forest floor properties are more shaped by tree species composition. The study, which analyzed 225 humus profiles across altitudes from 0 to 2000 meters in the Alborz Mountains, found that Mull abundance decreases in plain mixed forests compared to mountain pure forests, whereas Amphi forms increase. Mixed beech forests exhibit high frequencies of Oligomull and Leptoamphi, while Eumacroamphi, Eumesoamphi, and Pachyamphi are exclusive to pure beech forests. These patterns impact soil fertility, with higher nitrogen, microbial biomass nitrogen, and pH observed at lower altitudes under mixed forests than in pure forests at higher altitudes.

Bayranvand, M., Akbarinia, M., Salehi Jouzani, G., Gharechahi, J., & Alberti, G. (2021). Dynamics of humus forms and soil characteristics along a forest altitudinal gradient in Hyrcanian forest. iForest - Biogeosciences and Forestry, 14(1), 26–33. https://doi.org/10.3832/ifor3444-013