Quantifying carbon budgets of conifer Mediterranean forest ecosystems, Turkey

Aboveground biomass, aboveground litterfall, and leaf litter decomposition of five indigenous tree stands (pure stands of Pinus brutia, Pinus nigra, Cedrus libani, Juniperus excelsa, and a mixed stand of Abies cilicica, P. nigra, and C. libani) were measured in an eastern Mediterranean evergreen needleleaf forest of Turkey. Measurements were converted to regional scale estimates of carbon (C) stocks and fluxes of forest ecosystems, based on general non-site-specific allometric relationships. Mean C stock of the conifer forests was estimated as 97.8 +/- 79 Mg C ha(-1) consisting of 83.0 +/- 67 Mg C ha(-1) in the aboveground and 14.8 +/- 12 Mg C ha(-1) in the belowground biomass. The forest stands had mean soil organic carbon (SOC) and nitrogen (SON) stocks of 172.0 +/- 25.7 Mg C ha(-1) and 9.2 +/- 1.2 Mg N ha(-1), respectively. Mean total monthly litterfall was 376.2 +/- 191.3 kg C ha(-1), ranging from 641 +/- 385 kg C ha(-1) for Pinus brutia to 286 +/- 82 kg C ha(-1) for Cedrus libani. Decomposition rate constants (k) for pine needles were 0.0016 for Cedrus libani, 0.0009 for Pinus nigra, 0.0006 for the mixed stand, and 0.0005 day(-1) for Pinus brutia and Juniperus excelsa. Estimation of components of the C budgets revealed that the forest ecosystems were net C sinks, with a mean sequestration rate of 2.0 +/- 1.1 Mg C ha(-1) yr(-1) ranging from 3.2 +/- 2 Mg C ha(-1) for Pinus brutia to 1.6 +/- 0.6 Mg C ha(-1) for Cedrus libani. Mean net ecosystem productivity (NEP) resulted in sequestration of 98.4 +/- 54.1 Gg CO2 yr(-1) from the atmosphere when extrapolated for the entire study area of 134.2 km2 (Gg = 10(9) g). The quantitative C data from the study revealed the significance of the conifer Mediterranean forests as C sinks.