摘要
Accurately quantifying SOC （soil organic carbon） store in soils is considered fundamental to global climate change modeling, notably in soil forest ecosystems in relation to land cover/use change, forest fires and sustainable land management practices. Lebanese soils were described as relatively poor in organic matter content. This work used Landsat and IRS （Indian Remote Sensing） to classify land cover and land use, field survey to map the soil cover and assess carbon stock in the Lebanese soil and forest ecosystems and link the frequency of forest fires with the soil nature and land cover land use to assess the resulting risk of SOC loss from the soil pool. SOC density and stock was assessed using information from 450 soil profiles and the average OC content in a given soil type was calculated involving organic matter content in the soil, bulk density, soil thickness and the content of coarse fragments to produce the national SOC stock map. A total of 11 soil types （major classes） represented the mapping units describing the higher soil component or major classes were identified in Lebanon. The higher standard deviation observed in Luvisols reflects soil diversity, history and different management. Comparing the results of surface soil layer with the overall SOC density and stock in Lebanese soils showed a good correlation （0.98） between the OC stock within the upper soil layer and in the 100 cm depth, indicating the absolute role of the upper, biologically most active soil layer in the organic matter accumulation and carbon sequestration. Observation over a pilot area in the High Meten showed the calcareous soil group consists of Luvisols with associated Cambisols. Soil units representing the transition between the two soil groups are markedly affected by erosion-deposition processes. Pine occupies the largest area of forest （3,600 ha） followed by oak （1,800 ha） and mixed forest （1,200 ha）, representing 24.9%, 12.5 % and 8.2% of forest cover respectively. The analysis of SOC density in the soil of the pilot area showed relatively higher average organic matter accumulation rate in the soil under forest stands compared to shrubs and agricultural lands both at the soil surface （33.5 ton/ha） versus （30 ton/ha） and in the entire soil profile （99 ton/ha） versus （91 ton/ha） respectively. The burned area on these soil types reached 700 and 1,500 ha in 2003 while in the first soil group it did not exceed 50 ha.
