Changes in soil carbon sequestration along an altitudinal gradient in Salahodinkola Forest, Nowshahr

Understanding soil carbon fractions in relation to global warming is important for improving soil carbon management in natural forest ecosystems. Therefore, in this study we measured the contents of soil total organic carbon (SOC) in soil upper layers (0–20 cm) along a natural altitudinal transect (100–1400 m a.s.l.) in northern slope of Salaheddinkola forests, Nowshahr. Accordingly, vegetation data based on Braun-Blanquet method with some environmental properties were recorded in totally 77 plot with an area 400 m2 including seven classes of altitudinal gradient. Four ecosystem units were distinguished by using combined results of clustering (based on environmental data) and TWINSPAN (based on floristic data) as numerical classification analysis. Results analysis of variance showed that the amount of soil carbon sequestration had significant difference (0/05> P) in the four ecosystem units and third unit, which represents beech-hornbeam forests, to be allocated the largest amount of carbon sequestration (73/57 ton/ha), Because of the establishment of this unit in higher elevations and then high density of beech. Results of stepwise regression showed that nitrogen percentage, sand percentage and altitude were the most important factors affecting soil organic carbon content. Totally, the results of this study reiterate that the variability of soil carbon sequestration does not show a regular pattern along the altitudinal gradient and ecosystem units by exhibiting a proper distinction of environmental changes in habitat can be priority used in soil carbon stock variations study.