Effects Of Quality Improvement Management Measures On Carbon Sequestration And Sequestration Of Fir And Pinus Massoniana Plantations

Chinese has the largest area of industrial forests in the world,and is a major contributor to the increase in carbon stocks in China’s forest ecosystems and a major source of terrestrial carbon sinks.However,at present,China’s planted forests are facing problems such as soil decline and poor nutrient accumulation and circulation in the process of operation,which seriously affects their carbon sink function.Therefore,in order to further improve the carbon sink capacity of planted forests and better serve the dual carbon goals,it is urgent to carry out research on the impact of plantation forest quality improvement management measures on carbon sequestration and sequestration.In this study,the carbon sequestration capacity of fir and Pinus massoniana plantations and their response to management measures were explored from the perspectives of stand characteristics and soil properties through stand transformation,biochar and organic fertilizer addition measures,and the influence effect of carbon sequestration increase of different forest stands under biochar addition was clarified.The main findings are as follows:(1)Stand transformation measures increased the average breast diameter and annual growth rate of tree height of plantations,but the closure and crown width caused different degrees of decline.The average biomass growth of transformed forests increased significantly,and the biomass growth rate of fir and Pinus massoniana plantations increased by 3.5%.In terms of soil physical and chemical properties,the soil bulk density and moisture content and soil pH of fir and Pinus massoniana plantations increased significantly under the stand transformation measures.In the soil enzyme activities of modified forests,except for the insignificant effects on nitrate reductase(S-NR)and catalase(S-CAT),the other enzyme activities had different degrees of effects.The stand transformation measures reduced the soil organic carbon storage,and the soil organic carbon storage content in fir and Pinus massoniana plantations decreased by 15.85%and 25.57%,respectively.However,the carbon sequestration potential of planted forest stands was enhanced,and the carbon sequestration potential of different forest stands was relatively similar,with an increase of about 11%.(2)The short-term effect of biochar and organic fertilizer addition on the growth of understory vegetation was not significant,and the biomass of shrub layer and herbaceous layer under the B(biochar)measure in fir and Pinus massoniana plantations was slightly larger,and the BT(biochar and organic fertilizer)measure was taken next time.Different addition measures had different effects on soil bulk density,pH and moisture content of different forest stands.In terms of soil nutrient content,the soil organic carbon storage in the 0-45cm soil layer of fir and Pinus massoniana plantations increased significantly under different measures,and the effect was most significant under BT addition measures,which increased by 111.07%and 27.28%compared with CK(control),respectively.BT measures had the best effect on increasing the available nutrient content of topsoil in fir and Pinus massoniana plantations.(3)The addition of biochar and organic fertilizer had a significant effect on soil microbial characteristics,and had the greatest effect on the relative abundance of soil basidiomycetes in fir and Pinus massoniana plantations,weakened the dominance of the autotrophic phylum Chlorobentomycetes,and enhanced the dominance of the phylum Acidobacteriaceus.The effect of measure B on the a diversity index of bacteria and fungi in Pinus massoniana and fir plantations was higher than that of the other two measures,and the average diversity index of bacteria and fungi in fir soil α under T(organic fertilizer)and BT measures was higher than that of Pinus massoniana.At the OUT level,the effect of T measures on the soil bacterial β diversity index was significantly higher than that of the other two measures.Different fertilization measures increased the relative abundance of C-and N-cycle-related gene functions of soil microorganisms to varying degrees,and the relative abundance of T measures on Pinus massoniana plantations was more significant,while the effect of B measures was more significant in fir plantations.In summary,different management measures have a significant impact on carbon sequestration and sequestration of different plantations.Through the structural equation model,it can be concluded that stand transformation indirectly affects the carbon sequestration potential of plantations by affecting stand characteristics and soil properties,and although the stand transformation measures reduce the existing biomass and soil nutrient content of the stand,it is conducive to the improvement of stand productivity and carbon sequestration potential in the long run.In the addition of biochar and organic fertilizer,soil physical structure,soil nutrient and soil microbial community structure were improved to improve soil quality,thereby promoting the change of stand characteristics,and then enhancing the carbon sequestration and sequestration effect of planted forests.