水土保持碳汇内涵与测算方法OA北大核心CSTPCD

[Background]Soil and water conservation profoundly changes the land cover,surface structure,land use patterns and management measures of terrestrial ecosystems,which play an important role in carbon sink.The soil and water conservation measures can not only absorb CO2 from the air through its plant and soil carbon sequestration,but also reduces or controls the lateral transport of soil carbon,thus avoiding the erosion-induced CO2 emission.However,the studies on soil and water conservation measures preventing lateral soil organic carbon transport and vertical carbon emission remains misunderstood and unquantified.[Methods]Considering the role of soil and water conservation forest and grass measures,engineering measures and tillage measures in carbon cycle,this study followed the general idea of"mechanism elaboration-model construction-calculation by classification"that clarified the implications and pathways of soil and water conservation carbon sink,and established its calculating method and the index system.In addition,this study attempted to quantify the capacity of soil and water conservation carbon sink at the scale of China based on the distribution of biomass and soil carbon pool and soil erosion rates derived from national surveys,as well as ecosystem carbon density inventories and literature database.[Results]The soil and water conservation has multiple functions such as increasing carbon sink vertically,and fixing soil carbon via soil conservation(i.e.reducing lateral soil organic carbon loss)and consequently reducing CO2 emission.In 2021,the total vertical carbon sink of existing soil and water conservation measures in China was 1.54 × 108 t,contributing about 43.5％-56.5％to terrestrial carbon sink,of which forest and grass measures accounted for over 95％through plant and soil carbon sequestration.The amount of fixed carbon via soil and water conservation measures was 3.04 × 107 t in 2021 and have obvious cumulative effect and long-term effect,which must be considered.Overall,soil and water conservation measures absorbed atmospheric CO2(excluding the contribution of forest and grass measures through its plant and soil carbon sequestration)and reduced emission of 5.12× 107-6.23 × 107 t CO2 in 2021,accounting for about 4％-6％of the total terrestrial ecosystem carbon neutral in China,but this part has not been included in the national carbon accounting system and needs great attention.[Conclusions]These findings demonstrate that adoption of soil and water conservation measures can sequester carbon in soil and biota and reduce the risks of CO2 emission by both vertical and lateral paths,which are important to achieve carbon neutrality and mitigating climate change.