黄土丘陵区草地表层土壤固碳特征及影响因素

Topsoil Carbon Sequestration Characteristics and Influencing Factors for Two Grasslands in Loess Hilly Region

采用野外调查与室内分析相结合的方法,分析了黄土丘陵区长芒草(Stipa bungeana)、白羊草(Bothriochloa ischaemum)草地表层(0—20cm)土壤有机碳(SOC)及其与地形、土壤、植被等因子的相关性,以期揭示自然恢复过程土壤固碳特征及显著影响因子。结果表明,不同恢复年限长芒草群落土壤表层SOC平均含量14~18a显著增加,年均增加量为0.295g/kg;18~26a增加平缓,年均增加量为0.186g/kg;26~45a略微下降,33,45aSOC平均含量分别低于26a(8.92%,3.18%),差异均不显著。白羊草群落则表现25~40a平缓增加,年均增加量为0.054g/kg,40~45a以上显著增加,40aSOC平均含量低于45a以上29.38%,差异显著(p<0.05)。不同土层剖面,SOC含量均表现为土层0—10>土层10—20cm。土壤总SOC密度变化趋势与SOC平均含量一致。相关分析表明,长芒草、白羊草群落SOC平均含量随着恢复年限、地上生物量、地下生物量、全氮的增加而增加,随着海拔、容重的增加而减小。随着恢复年限的增加,长芒草、白羊草群落土壤表层SOC存在明显固存效应,海拔、恢复年限、地上生物量、地下生物量、全氮、容重为显著影响因子。

Combing field investigation with laboratory analysis, we studied soil organic carbon（SOC） content in topsoil（0--20 cm） with different ages of the Stipa bungeana and Bothriochloa ischaemum grassland communities and presented the correlations of SOC content with geography, soil and vegetation characteristics of the communities in the loess hilly region, in order to proclaim soil carbon sequestration characteristics and notable influencing factors in the natural grassland restoration process. For the Stipa bungeana grassland, average SOC content dramaticlly increased from the 14 a to 18 a, with an average annual increment of 0. 295 g/kg. The average SOC content gently increased first from the 18 a to 26 a, with an average annual increment of 0. 186 g/kg, and then gradually decreased from the 26 to 45 a. The average SOC contents in 33 a and 45 a were 8.92% and 3.18~ lower than that in the 25 a, respectively, but the difference was not significant. For the Bothriochloa ischaemum grassland, average SOC content gently increased from the 25 a to 40 a, with an average annual increment of 0. 054 g/kg. The average SOC content obviously increased from the 40 a to 45 a, and the average SOC content in the 40 a was only 29.38% of that in the 45 a, and the difference was significant（p^0.05）. SOC content in 0--10 cm soil layer was higher than that in 10--20 cm soil layer. Correlation analysis indicated that average SOC contents for Stipa bungeana and Bothriochloa ischaemum grasslands increased with the increases in restoration year, aboveground biomass, underground biomass and soil total nitrogen, and decreased with altitude and soil bulk density. Therefore, topsoils of Stipa bungeana and Both- riochloa ischaemurn grasslands show the obvious function of carbon sequestration. Altitude, restoration year, aboveground biomass, underground biomass, soil total nitrogen and soil bulk density are the significant factors.