| The spatial heterogeneity of Guangdong Province brings great influence on the carbon sequestration rate of secondary forests,but previous studies mainly rely on limited field field sample point observations,which are limited in spatial extent and temporal duration,and cannot well reveal the influence mechanism of carbon sequestration rate of secondary forests,and its driving factors are still unclear,which seriously restricts the accurate estimation and prediction of future carbon sink capacity.Using the advantages of remote sensing technology in spatial and temporal monitoring,this study reveals the spatial and temporal evolution of above-ground biomass carbon of forest resources in Guangdong Province based on high-resolution remote sensing data such as forest above-ground biomass carbon data,secondary forest plantation year data,meteorological data,and geological and soil geospatial data,and takes secondary forests in Guangdong Province as the main subject of study.The spatial and temporal evolution of above-ground biomass carbon in secondary forests of Guangdong Province was characterized by four major drivers: topography(slope,slope orientation),climate(temperature,precipitation,soil moisture,short-wave radiation),soil texture(total soil carbon content,total soil nitrogen content)and stand(stand age,tree species),which contributed to the rate and spatial pattern of above-ground biomass carbon accumulation in secondary forests of Guangdong Province.Based on the contribution characteristics of the above influencing factors,scenario analysis was used to predict the future carbon sequestration potential of above-ground biomass in secondary forests in Guangdong Province under four scenarios: optimal efficiency,easy to plant,maximum storage,and easy to survive.The following main conclusions were drawn:(1)The spatial and temporal heterogeneity of above-ground forest biomass carbon in Guangdong Province is remarkable.Spatially,above-ground forest biomass carbon in the province shows a distribution pattern of high in the north and low in the south and high around and low in the centre,with high values of above-ground biomass carbon mainly distributed in northern Guangdong,while smaller carbon is mainly distributed in the Pearl Rive r Delta.In terms of temporal changes,the total above-ground biomass carbon of forests in Guangdong Province increased by 0.77*106ha in 2018 compared with 2010,with the most obvious increase in the area of medium(40-60 Mg C/ha)and higher(60-80 Mg C/ha)above-ground biomass carbon,and more significant spatial clustering of high high and low.(2)In Guangdong Province as a whole,the above-ground biomass carbon in secondary forests tends to increase rapidly with the age of the forest and then decreases gradually,which is called the accumulation rate of aboveground biomass carbon in secondary forests.Through the mechanism analysis,the accumulation rate was significantly related to slope,total soil carbon content,total soil nitrogen,soil moisture,short-wave radiation,precipitation and temperature.The accumulation rate of above-ground biomass carbon in secondary forests was significantly positively correlated with slope,precipitation,total soil carbon content and total soil nitrogen content,and negatively correlated with soil moisture,short-wave radiation and temperature.In addition,tree species and slope orientation also had an effect on the rate of above-ground biomass carbon accumulation in secondary forests.The order of importance of the driving effects was: stand age > slope > rainfall >temperature > soil moisture > slope orientation > total soil nitrogen content >shortwave radiation > total soil carbon content > tree species.(3)For the four regions of eastern Guangdong,western Guangdong,northern Guangdong,and the PRD,apart from the common feature that forest age is the most important influence on above-ground biomass carbon,while tree species and soil elemental content are less influential,the contributions of the remaining drivers vary considerably.Topography was the most important influence after forest age in northern,eastern and western Guangdong,with climate factors having a relatively minor influence.In the PRD region,however,climate has a much greater influence on above-ground biomass carbon than topography.In addition to this,there are also some differences in soil texture.(4)Combining the geospatial background variation characteristics of Guangdong Province and the results of previous contributions,it is predicted that by 2050 the overall above-ground biomass fraction in Guangdong Province can add 15.84 ± 0.72 Tg C under the optimal efficiency scenario;17.20 ± 0.55 Tg C under the easy cultivation scenario;55.20 ± 2.92 Tg C under the easy survival scenario;and 62.17 ± 2.55 Tg C under the maximum storage scenario.The maximum carbon addition in the maximum storage scenario is62.17 ± 2.55 Tg C.(5)In 2050,under the maximum storage scenario,the carbon rese rves exceeding 0.48 Tg C will increase from 7 counties in 2020 to 43 counties and districts,accounting for about 35%,with the number of counties and districts with carbon sequestration greater than 0.82 Tg C increasing from 0 to 20.The largest change in carbon sequestration currently is in Yingde City,with carbon storage increasing from 0.70 Tg C to 24.95 Tg C,an increase of about 30 times.To achieve certain carbon sequestration targets,different afforestation combinations can be proposed to better suit the development of Guangdong Province based on the carbon sink potential under different scenarios.The results of the study can provide a scientific basis for sustainable forest management and quality development in Guangdong Province. |
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