Abstract
Afforestation of grasslands is increased in Fandoghloo region of northwestern Iran, which has been used for grazing. Carbon
(C) stocking of pure and mixed Pinus nigra, Cedeus libani and Picea abies afforested stands (20 years-old) in Ardabil, Iran
was assessed. C stocking of tree biomass and litter were defined based on plot-scale measurements. Soil organic carbon (SOC)
stocking was determined using soil cores at three depths 0-15, 15-30 and 30-50 cm. An increase in the total ecosystem carbon
stock after the afforestation was recorded. The highest total C stocking was estimated to be 55.57 Mg ha-1
for the mixed P.
nigra – C. libani and it was 25.006 Mg ha-1
in the degraded rangeland. The aboveground biomass C varied from 2.4 Mg ha-1
in the degraded rangeland to 19.28, 15.1, 6.17, 4.55, and 3.87 Mg ha-1
in the P. nigra-C. libani, P.nigra, P. abies- P.nigra, C.
libani and P. abies stands, respectively. The amount of litter carbon stock ranged from 0.53 Mg ha-1
in the degraded rangeland
to 3.51, 3.06, 2.03, 1.55, 1.41 Mg ha-1
in the P. abies - P. nigra, P. nigra - C. libani, P. nigra, C. libani and P. abies stands,
respectively. The soil carbon stock increased from 21.41 to 30.11, 28.58, 28.41, 27.45 and 25.43 Mg ha-1
in the C. libani, P.
nigra, P. nigra - C. libani, P. abies - P.nigra and P. abies stands, respectively. Significant interactions were observed between
stand and soil depth on carbon stock after afforestation with coniferous species in grassland. According to the results, the major
ecosystem C pool is attributed to aboveground biomass. The total ecosystem C difference between the degraded rangeland and
mixed P. nigra - C. libani stand was 30.56 Mg ha-1
. The highest SOC accumulation was observed in the surface layer of the
C. libani (34.95 Mg ha-1
), but the accumulation rate is species dependent. The results highlighted the importance of coniferous
afforestation on degraded grassland that will most presumably improve the amount of carbon stock and therefore, decrease the
negative impacts of increasing CO2 concentrations. As a matter of fact, the selection of appropriate species and plantation will
be considered in the next afforestation projects.
