Study On Carbon Storage And Its Influencing Factors Of Different Stand Structures In Ziwuling Forest Region

Forest is the largest carbon pool and the most important carbon sink in the terrestrial ecosystem,playing a pivotal role in the global carbon cycle.In recent years,the policy of returning farmland to forests implemented on the Loess Plateau has achieved significant results,with a significant increase in vegetation coverage and improvement in the ecological environment in the northwest region of China.With the proposal of the"double carbon"policy,higher requirements have been put forward for the quality of carbon sink.Therefore,scientific and accurate assessment of carbon storage and prediction of carbon sink capacity,analysis of the differences in carbon sequestration capacity under different forest types and their causes have certain practical significance for carbon sink enhancement measures and shelter forest construction.Based on the measured data of sample plots,this paper uses remote sensing images and field measurements to accurately estimate the regional carbon storage,calculates the carbon storage of vegetation,soil and litter carbon pools,analyzes the correlation among carbon pools,analyzes the causes of differences among carbon pools,and estimates the carbon sink rate of small area ecosystems through vorticity correlation method,in order to provide scientific basis for plantation and improvement.The main progress made is as follows（1）The total carbon storage within 505ha of the study area is about 66666.57t.The forest type and altitude have significant effects on the distribution of carbon density.The average carbon density is shown as mixed forest(135.87t·hm^-2)>broad-leaved forest(131.97t·hm^-2)>coniferous forest(113.62t·hm^-2).The highest carbon density of pure forest is in the middle altitude of1040m～1140m,and the highest carbon density of mixed forest is in the high altitude of1140m～1240m.Among the major carbon pools,the soil carbon pool has the highest carbon density,with an average carbon density of about 81.70 t·hm^-2.The vegetation carbon pool has the second highest average carbon density,with an average carbon density of about 35.59 t·hm^-2.The soil carbon density is about twice that of vegetation carbon density.The correlation between the carbon density of each carbon pool and the total carbon density is in descending order:soil carbon density>vegetation carbon density>litter carbon density,with soil carbon pool having the greatest impact on the carbon density of the ecosystem.（2）There are great differences in soil structure and nutrients among different forests.The stability of soil aggregates showed significant differences between different forest types and altitudes.MWD and GMD showed broad-leaved forest>mixed forest>coniferous forest among different forests,and showed high altitude>low altitude>medium altitude between different altitudes.The difference of soil C/N in different forest types is mixed forest>broad-leaved forest>coniferous forest,and it is low altitude>high altitude>medium altitude in different altitude gradients.The soil enzyme activities of different stands also showed as mixed forest>broad-leaved forest>coniferous forest.The results indicate that mixed forests have stronger soil stability,higher soil nutrient content,and a more suitable soil environment for microbial survival,indicating that the structure of mixed forests is better than that of pure forests.（3）The carbon flux observation results indicate that the ecosystem exhibits significant carbon sequestration effects in both summer and winter,with a carbon sequestration rate of about 1t·hm^-2·a in summer and about 1/10 of that in winter.