Assessment Of Biomass And Carbon Stock Of Different Stand Ages In Subtropical Chir Pine(Pinus Roxburghii) Forest Of Pakistan

Forest biomass carbon plays a significant role in the global carbon cycle as well as climate change mitigation because of the higher potential of storing carbon than other terrestrial ecosystems.Studies regarding biomass and carbon stock have investigated in various forest ecosystems at the regional and continental scale.However,the quantitative relationship between carbon sequestration potential and stand ages of Chir pine(Pinus roxburghii)forest is not documented in Pakistan.Using field inventory data,this study underlines the patterns of biomass and carbon allocation across a chronosequence of Chir pine forest in different carbon pools.Based on the uniform shelterwood silvicultural management system,the forest was classified into three stand age classes,representing the young stand(<50 years),mature stand(50-75 years)and over-mature stand(>75 years).Using stratified random sampling,7 sample plots of each size 20×30 m2 were laid out in each stand age class.In each sample plot,the tree diameter at breast height and tree height were measured for growing stock volume and then,biomass carbon was calculated.Similarly,in each plot,the understory vegetation,deadwood and litter were collected randomly from 1m2 subplots and oven dried it for 48 hours at 72? for biomass carbon measurement.The soil samples were taken at a depth of 0-15 cm and 15-30 cm from each plot by following IPCC guidelines and carbon value was determined by using the titration method.The results showed that total tree biomass(above-ground and below-ground)distribution of Chir pine forest of the young,mature and over-mature stand was recorded at 80.0±12.4(Mg ha-1),343.1±167.6(Mg ha-1)and 529.5±176.8(Mg ha-1)respectively,demonstrating a significant increasing trend in biomass from young stand age trees to over-mature stand age trees.Similarly,litter,deadwood and understory vegetation biomass carbon showed an increasing pattern of changes.The soil organic carbon stocks of the Chir pine forest ecosystem at a depth of 0-30 cm in young,mature and over-mature stand was 50.0±11.8(Mg C ha-1),46.2±15.7(Mg C ha-1)and 44.4±9.1(Mg C ha-1)respectively.However,the soil carbon showed gradually decreasing trend from young to over-mature stand due to the management and logging operations in the mature and over-mature stands.Altogether,the results highlighted that the mean carbon values of all components varied between 90.3(Mg C ha-1)in the young stand to 309.5(Mg C ha-1)in the over-mature stand.Furthermore,our results confirm that the current management operations such as cutting,thinning,tending,may affecting the tree,forest floor,and soil carbon.Therefore,we suggesting different protection measures such as reduced impact logging,soil conservation through mulching,and maintaining understory vegetation and forest cover through regeneration,control grazing and effective management of forest fire should be considered.