黄土丘陵区小流域土壤碳氮比的变化及其影响因素

The Changes and Influencing Factors of Soil C:N Ratio in Small Watershed of Hilly Region of Loess Plateau

研究土壤C∶N的变化有助于深入理解土壤有机碳氮的积累过程及其土壤质量的变化趋势。以黄土高原丘陵沟壑区砖窑沟小流域为单元,基于地貌类型和土地利用方式两大因素,采集737个土壤样品,研究流域内土壤C∶N的变化差异及其影响因素。梁峁坡上,林地和草地0～20 cm土层的土壤C∶N分别是农田土壤C∶N的1.13和1.03倍;沟坡上,林地、草地和农田土壤的C∶N分别为13.88、12.58、9.02。农田条件下,梁峁坡、沟坡和沟谷的土壤C∶N分别为10.34、9.02和10.77;林地条件下,沟坡和梁峁坡的土壤C∶N分别为13.88、11.67;草地条件下,沟坡土壤C∶N是梁峁坡土壤C∶N的1.19倍。同一地貌类型或土地利用方式条件下,土壤C∶N均呈现表层大于深层的趋势,0～20 cm和20～40 cm土层的土壤C∶N分别是40～100 cm土层土壤C∶N的1.05～1.17和1.16～1.42倍。

Investigated the changes of soil C ： N ratio can help us to understand accumulation of soil organic carbon and nitrogen and tendency of soil quality changes. Based on landforms and land use types, 737 soil samples were collected for investigating the changes of soil C ： N ratio and its＇ influencing factors at a typical small watershed in the hilly region of the Loess Plateau. The results showed that in the condition of 0 -20 cm soil layer, in ridge slope soil C ： N ratios of woodland and grassland were 1.13 and 1.03 times that of those cropland ; in gulley slope the soil C ： N ratios of woodland, grassland and cropland were 13.88, 12.58 and 9. 02 respectively; in cropland the soils C ： N ratios of gulley slope, ridge slope and valley bottom were 9.02, 10. 34 and 10. 77 respectively; in woodland the soils C ： N ratios of gulley slope and ridge slope were 13. 88 and ll. 67 respectively;in grassland the soil C ： N ratio of gulley slope was 1.19 times that of the ridge slope; in the same landforms or land use types, soil C ： N ratio was larger in the sur- face layer than in the deep layer, soil C ： N ratios in 0 -20 cm and 20 -40 cm soil layer were 1.05 to 1.17 and 1.16 to 1.42 times that of those in the deep layer.