| Soil organic carbon（SOC）is an important part of the global carbon cycle,and it is also an important indicator of soil quality and land productivity evaluation.The total area of the world’s existing cultivated land accounts for about 11%of the world’s total surface area,and the cultivated land has great potential for carbon sequestration and the ability to mitigate climate change.Current studies in different regions have shown that the organic carbon content in agricultural soils worldwide is on a downward trend,and increasing soil organic carbon content in farmland is the key to promoting sustainable agricultural development and global carbon sinks.Terraces are widely distributed in mountainous and hilly areas around the world,and can effectively inhibit soil erosion,increase soil moisture,improve soil quality,and may have a positive impact on soil carbon pools.At the same time,agricultural management and vegetation restoration measures have also had an impact on the soil carbon pool of the constructed terraces.In order to understand the impact of agricultural activities and vegetation restoration measures on soil carbon pool changes in terraced fields,this study established an observation system in typical terraced fields on the Loess Plateau,systematically sampled the terraced fields in October 2020,and collected samples of terraced fields（including different crops and different restored vegetation types）and soil profile samples at a depth of 0-100cm on slopes,measured the SOC content,soil moisture,and soil particle size data,and clarified the impact of terrace construction,agricultural management,and vegetation restoration on SOC through comparative research methods,and aimed at How to carry out agricultural management and increase soil carbon sequestration in terraced areas.This study mainly draws the following conclusions:（1）Terracing had a positive impact on soil moisture retention and SOC increase.In the 0-100 cm soil layer,the average soil moisture of terraces was higher than that of sloping land（24.2%>21.3%）.Horizontal terraces constructed for more than 30 years had a significant increasing effect on deep soil water.The soil clay particles and soil powder particles of terraces were higher than those of sloping cultivated land,and the soil sand content was lower than that of sloping cultivated land.The average SOC content of terraces 0-100 cm was 1.4 times higher than that of sloping farmland,and terrace construction had an important role in increasing SOC content.（2）Terraced orchard abandonment is beneficial for soil moisture increase,but as vegetation recovery takes a long time,abandonment will lead to a decrease in SOC content within 1-2 years.Soil moisture in abandoned apple tree terraces was higher than in-use terraces,and the average soil moisture in the 0-100 cm soil layer of abandoned terraces increased by 3.25%compared to in-use terraces.The most significant increase in soil moisture in the vertical direction was in the top soil layer（0-20 cm）and in the70-100 cm soil layer.The SOC content of the terraces abandoned for 1-2 years was slightly lower than that of the terraces in use,but the difference was small,0.7 g?kg-1.There was a significant decrease in SOC content in the top 0-20 cm layer after abandonment.（3）The agroforestry complex planting structure was conducive to increasing the SOC content.The SOC content of planted apple trees-beans and apple trees-potatoes was higher than that of beans and potatoes planted alone(5.4 g?kg-1>4.5 g?kg-1and 6.7g?kg-1>5.2 g?kg-1).（4）The planting of ecological restoration herbs on terraced or levelled areas could better enable them to use soil moisture and have a better carbon sequestration effect.The planting of Pinus tabuliformis will be more beneficial to SOC accumulation in silvicultural land.The average SOC content in the 0-100 cm soil profile was higher in afforested land than in in-use terraces,abandoned terraces,natural grassland and sloping land(9.06 g?kg-1>7.04 g?kg-1>6.4 g?kg-1>6.02 g?kg-1>4.9 g?kg-1).The SOC content of Pinus tabuliformis was higher than that of Robinia pseudoacacia.The significant difference in SOC between the two tree species was mainly at 0-70 cm depth. |
