黄土高原半干旱区不同封育年限草地生态系统碳密度

Ecosystem Carbon Density of Grasslands under Different Grazing Exclusion Ages in Semiarid Region of the Loess Plateau

本研究以云雾山国家级自然保护区典型草原为研究对象,分析了不同封育年限长芒草（Stipa bungeana）草地生态系统碳密度及其库间分配规律。主要结果如下：放牧和封育5年、9年、15年、22年、25年、30年的草地生态系统碳密度变化范围为212.72-350.42 Mg C·hm^-2,其中,封育30年草地最高,放牧草地最低,且显著低于各封育草地（P〈0.05）。草地植被碳密度以封育15年最高,达到15.65 Mg C·hm^-2,放牧草地最低,仅为7.82 Mg C·hm^-2。在库间分配上,根系碳密度所占平均比例达到82.56%。草地土壤碳密度在204.90-337.36 Mg C·hm^-2之间变化,随封育年限的延长持续增加,封育草地土壤碳密度是放牧牧草地的2.33-2.64倍。以上结果表明,封育可显著提高黄土高原半干旱区草地生态系统碳密度,但过长时间的封育阻碍草地的更新和固碳潜力发挥,合理利用才能促进草地生态系统持续健康发展。

In this study,grazing grassland and grasslands with different exclusion ages（5,9,15,22,25 and 30years）of Stipa bungeana at Yunwu Mountain National Nature Reserve were selected to analyze ecosystem carbon densities and their distribution among discrete pools.Grassland ecosystem carbon densities ranged between 212.72 Mg C·hm^-2 and 350.42 Mg C·hm^-2,the highest in grassland with 30-year exclusion and the lowest in grazing grassland,which was significantly lower than that of exclusion grasslands（P 0.05）.Grassland with 15-year exclusion had the highest vegetation carbon density,15.65 Mg C·hm^-2,however,grazing grassland had the lowest,7.82 Mg C·hm^-2.In addition,the average proportion of root carbon density was 82.56%.Soil carbon densities increased with increasing exclusion ages,ranged from 204.90 Mg C·hm^-2 to 337.36 Mg C·hm^-2,and exclusion grasslands were 2.33-2.64 times greater than that of grazing grassland.These results showed that exclusion significantly increased ecosystem carbon density of grassland in semiarid region of the Loess Plateau,however,long-term exclusion would exert negative influences on grassland renewal and carbon sequestration potential,and reasonable utilizations were suggested.