Estimation of soil carbon pools in the forests of Khyber Pakhtunkhwa Province, Pakistan

Forest soils have high carbon densities compared to other land-uses. Soil carbon sequestration is important to reduce CO2 concentrations in the atmosphere. An effective climate change mitigation strategy involves limiting the emissions of greenhouse gases from soils. Khyber Pakhtunkhwa is the most forested province of Pakistan, hosting about one-third of the country's 4.5x10(6) ha forest area. Soil organic carbon in the province's forests was estimated through a field-based study carried out during 2014-17 covering the whole province. Data was collected from 373 sample plots laid out in different forest types using a stratified cluster sampling technique. The total quantity of soil organic carbon was estimated at 59.4x10(6) t with an average of 52.4 +/- 5.3 t/ha. About 69% of the total soil carbon is present in temperate forests. Subtropical broad-leaved and subtropical pine forests constitute 11.4% and 8.8% of the soil carbon stock respectively. Similarly, subalpine and oak forests have respective shares of 5.1% and 5.7% in the soil carbon pool. The lowest carbon stock (0.1%) was found in dry-tropical thorn forests. The highest soil carbon density was found in subalpine forests (69.5 +/- 7.2 t/ha) followed by moist temperate forests (68.5 +/- 6.7 t/ha) and dry temperate forests (60.7 +/- 6.5 t/ha). Oak forests have carbon density of 43.4 +/- 7.1 t/ha. Subtropical pine, subtropical broad-leaved and dry tropical thorn forests have soil carbon densities of 36.3 +/- 3.7, 32.8 +/- 6.2 and 31.5 +/- 3.5 t/ha, respectively. The forests of the Khyber Pakhtunkhwa province have substantial amounts of soil carbon which must be conserved for climate change mitigation and maintenance of sound forest health.