Effects Of Commercial Harvest Exclusion On Forest Composition,Structure And Spatial Distribution Of The Great Xing'an Mountains

Boreal forests retain larger carbon reserves than other biomes in the world.Boreal forests of China are in the Great Xing'an Mountains,contain approximately 24~31% of the total forest carbon storage of China,and thus play an important role in maintaining the national carbon balance.Timber harvest has been a major anthropogenic disturbance in boreal forests,affecting forest structure and aboveground forest biomass over the long term.High-intensity harvest resulted in simplification and homogenization of forest structure and composition in the past.Therefore,the Natural Forest Conservation Policy and the Commercial Harvest Exclusion Policy were successively implemented in 2000 and 2014,respectively,to balance the needs of ecological restoration and timber supply.The objective of this study was to investigate long-term effects of Commercial Harvest Exclusion on the structure and biomass of boreal forests in Northeastern China.To do so,we simulated the effects of Natural Forest Conservation and Commercial Harvest Exclusion on forest composition,structure and spatial distribution using a spatially explicit forest landscape model(LANDIS PRO).We initialized the model using 2000 forest inventory data(second and third tier data)and conducted simulations for the Great Xing'an Mountains from 2000 to 2100.The major conclusions were as following:1)Results suggested that the initialized forest landscapes from the 2000 forest inventory data represented the forest composition and structure of year 2000 adequately.Density and basal area between the initialized results and forest inventory data in 2000 were consistent(P < 0.01),suggesting that the initialization captured the real forest landscapes,and harvest results adequately represented real harvest events.2)Larch and birch were dominant species,whereas a low proportion of aspen and spruce was present.Compared to the Natural Forest Conservation scenario,the Commercial Harvest Exclusion reduced the diversity of tree species by raising the proportions of the dominant species(larch and birch)and reducing the proportions of protected rare species(pine and spruce).There was a significant effect on forest composition in the medium and long-term periods.Overall,basal area was higher and density was lower under the Commercial Harvest Exclusion scenario than those under the Natural Forest Conservation scenario.Commercial Harvest Exclusion strongly decreased tree abundance in the early stage and increased their abundance in the late,old-growth stage.Compared to the Natural Forest Conservation scenario,the simulated biomass and rate of forest regeneration increased under the Commercial Harvest Exclusion scenario across all simulation periods.Commercial Harvest Exclusion helped increase overall forest biomass,but reduced the biomass of rare and economically important species such as pine and spruce,suggesting that greater intensity of sivilcultural treatments may be needed.3)Our results indicated that the spatial distribution of species changed with the whole simulation period.Commercial Harvest Exclusion increased coniferous species(larch,pine,spruce)spatial distributions and decreased broadleaf species(birch,aspen)spatial distributons.These results could help develop forest management plan and identify alternative management policy for the the Great Xing'an Mountains.