Research On Forest Carbon Sink Assessment System In Ecological Counties

At present,global warming is one of the greatest threats to mankind,and the continuous increase in the concentration of greenhouse gases,especially CO₂,is the main cause of global warming.The increasing concentration of greenhouse gases in the atmosphere,especially CO₂,will seriously damage the ecological balance of the earth and lead to a series of serious disasters.Therefore,it is imperative to reduce greenhouse gas emissions and combat climate change.The carbon sequestration function of forest ecosystem services can fix carbon in the vegetation and soil of forests,effectively reducing the concentration of CO₂ in the atmosphere,alleviating the climate problem of global warming and protecting the ecological balance of the earth.In addition,as the basic unit of economic and social development and governance in China,the assessment methods for forest carbon sinks in counties are not yet perfect,and research on forest management with the goal of increasing forest carbon sequestration needs to be supplemented.Therefore,the search for an accurate assessment method for forest carbon sinks in counties can improve the global climate problem,bring into play the important role of forest carbon sinks,and provide a scientific basis for the promotion of"double carbon"work in the region and the country.Taking Wuning County of Jiangxi Province as an example,this study calculated the biomass,carbon density,net productivity and carbon sequestration capacity of various forest land types in Wuning County based on the field survey data of 120quadrates combined with the forest resource class data and remote sensing image data from 2016 to 2020,and established the mixed growth model of forest carbon storage at the county scale.The forest carbon storage and forest carbon sink during 2016-2020were estimated by using reserve change method,and the temporal and spatial pattern of forest carbon sink in Wuning County was analyzed.The following conclusions are drawn:（1）The average biomass of each stand type in Wuning County ranged from3.78～372.71 t·hm^-2,and the net productivity ranged from 3.82～28.10 t·hm^-2·a^-1.Carbon density of each forest ranged from 68.76～240.53 t·hm^-2.The carbon sequestration capacity of each forest ranged from 6.13～16.58 t·hm^-2·a^-1,and the carbon sequestration value of each forest ranged from 0.59～1.59 Ten thousand yuan·hm^-2.From strong to weak,the carbon sequestration ability of each stand type was in order as follows:Liquidamber>Pinus elliottii>broadleaved mixed forest>Betula>non-wood product forest>Other hard broad leaf>Castanopsis eyrei>Cunninghamia lanceolata>Pinus massoniana>coniferus mixed forest>Other soft broad leaf>Bamboo>Quercus>shrub.（2）In 2020,the carbon reserve of Wuning County was 33.95 Tg C,and the soil organic carbon reserve was 12.78 Tg C（37.64%）,the total forest net productivity was360.42×10⁴ t·a^-1,and the total carbon sequestration was 270.41×10⁴ t·a^-1.The total annual carbon sequestration value is about 2.6 billion yuan.Combined with the forest area of Wuning County,the carbon sequestration amount per hectare is 10 t,creating carbon sequestration value of 0.96 million yuan.（3）From the perspective of age,the common rule of biomass and carbon density per unit area of each age group was overripe forest>mature forest>near mature forest>middle age forest>young forest,and the general trend of forest net productivity and carbon sequestration capacity was young forest>middle age forest>near mature forest>mature forest>mature forest>mature forest>over-mature forest.The large proportion of young and middle-aged forests and strong carbon sequestration capacity indicate that the low hilly area has great potential for carbon sequestration in the next 40 years.（4）The five-year spatial distribution of carbon density in Wuning County is basically consistent,with higher carbon stocks in the western and southern forest ecosystems and lower carbon stocks in the northeast.Except for the southeastern part which is a carbon source area,most of the carbon sinks in the forest ecosystems of Wuning County are positive,with high carbon sink areas mainly in the northeast and low carbon sink areas in the central part.As latitude increases,the forest’s ability to sequester carbon gradually becomes weaker,and this distribution characteristic is basically consistent with the distribution characteristics of heat,moisture,and NEP in China.（5）From 2016 to 2020,the spatial distribution characteristics of carbon storage altitude in Wuning County were as follows:with the increase of altitude,forest carbon storage showed a trend of first increase and then decrease.The spatial distribution characteristics of carbon storage slope in Wuning County were as follows:with the increase of slope,forest carbon storage showed a trend of first increasing and then decreasing.The spatial distribution characteristics of forest carbon storage in Wuning County were as follows:forest carbon storage was more distributed in negative slope and sunny slope,but less in non-slope area.The spatial distribution characteristics of carbon storage soil layer thickness in Wuning County are as follows:with the increase of soil layer thickness,forest carbon storage also increases gradually.