Effects Of Land Use/Land Cover Change On Forest Biomass Carbon Dynamics In Himalayan Forests Of Pakistan

Himalayan forests of Pakistan are housing a rich floral and faunal diversity.The study area has three forest types i.e.Sub-tropical broadleaved forest(STBLF),subtropical chipine forest(SCPF)and moist temperate forest(MTF).They have more than 1700 species of flowering,more than 50 species of grasses 53 species of ferns.The subtropical broad-leaved forests usually found at elevation of 500m-1200m,are rich in tree species,shrubs and thorny vegetation,while the subtropical chirpine forest are located at range from 1000m-2500m which is dominated by Pinus roxburghii.The Moist Temperate forest in Pakistan ranges at altitude from 1500m-3000m,naturally regenerated forest having mature tall growing conifer species and new regeneration of almost all age classes like Pinus Wallichiana,Cedrus deodara,Abies pindrow,Picea smithiana etc.(1)The recent expansion of human activities resulting from illegal and uncontrolled harvesting,agricultural activities and urbanization has caused Land use/Land Cover Change(LULCC),which is a cause for concern.By using Remote sensing(RS)data,Geographic Information System(GIS)modeling we examined LULCC.In our study area Land use and land cover changes showed forest land changed from 40,936.77 hectares to 36709.23 hectares,agricultural land 4220.46 hectares to 10374.64 hectares,barren mountains 14,407.29 hectares to 9456.56 hectares and built-up area from 1,497.60 hectares to 5395.12 hectares in the studied period(1998-2028).The average annual biomass and carbon loss was 38.45 Gg ha-1y-1 and 26.02 GgC ha-1 yr-1.The Forest inventory results showed that biomass was 426.94± 81.56 Mg ha-1,268.22± 81.56 Mg ha-1 and 123.36 ± 81.56 Mg ha-1 in moist temperate,subtropical chirpine and subtropical broad-leaved forests respectively.Meanwhile,carbon was respectively 257.92± 40.187 Mg C ha-1,179.5±40.187 MgC ha-1 and 116.54± 40.187 MgC ha-1 in moist temperate,subtropical chirpine and subtropical broad-leaved forest.(2)Due to high temperatures and dry summer conditions in the study area forest fires are of a regular occurrence.These fires emit carbon dioxide and other greenhouse gases into the atmosphere which retroact on the climate and ecological systems.We also studied the carbon dioxide emission estimates from forest fires and risk zones in subtropical and temperate forests of Pakistan.CO2 emission was calculated using known burned area,combustion factor(CF)and burning efficiency(Ef),of our study area following the guidelines of IPCC for CO2 emission calculation.Fire risk zones assessment was performed.Results showed that average dry organic matter in the study area is 13837(±5774.64 std.dev.)g.m 2,while average annual carbon dioxide emission to be 7280(±5369 std.dev.)Gg CO2 and 56.6%average annual rate of CO2 emission increase.Additionally,over 56%of the area or 9.33%(extreme risk zone)and 45.20%(high risk zone)is threatened by fire.(3)To know the trend of Land use change(LULCC)particularly the conversion of forest to other land uses and the scale of forest carbon shifts in the protected area i.e.Margallah Hills National Park(MHNP)which is present in our study area,we selected the year 1990,2000,2010,2017.Our results showed that during the period from 1990 to 2017,the area under dense forest decreased by 11.14%;(0.41%yr-1),while the area under open forests increased by 4.28%(0.15%yr-1).Similarly,agricultural land and settlements increased by 53.17%(1.96%yr-1)and 67.78%(2.51%yr-1)respectively,during the same period.The conversion of forests into other land uses resulted in the reduction of carbon value.In 1990,carbon loss is estimated at 5531.5 MgC yr-1(7.22%)of the total carbon pool.Overall,land use change released 154 GgC(5.70 GgC yr-1).The main driving forces of the of LULCC and Biomass carbon loss are urbanization due to population pressure,Deforestation and illegal encroachment in the forest Land and forest fire.