封育对荒漠草原土壤有机碳及其活性组分的影响

以空间序列代替时间序列的方法,选取未封育、封育3、5、7及10年的荒漠草原为对象,研究封育对荒漠草原土壤总有机碳、颗粒有机碳、水溶性有机碳和易氧化有机碳的影响。结果表明:封育对5~10 cm、10~20 cm和20~40 cm土层总有机碳影响显著(P<0.05),其含量随封育年限的延长总体呈增加的趋势,分布范围为2.24~4.52 g· kg^-1,以封育7和10年的荒漠草原较高。封育对荒漠草原土壤颗粒有机碳无显著影响(P>0.05);可溶性有机碳含量在0~5 cm、5~10 cm和20~40 cm土层随封育年限的延长呈先下降后上升的趋势,均以未封育荒漠草原最高,分别为0.59,0.49 和0.56 g·kg^-1,封育5和7年的荒漠草原较低;易氧化有机碳含量以封育7年的荒漠草原较高,总含量为2.48 g·kg^-1。封育7年是退化荒漠草原自然恢复演替过程中的一个转折。

Effects of enclosure on the soil organic carbon and its active components in desert steppe grassland

This experiment used spatially distributed sites which had been fenced for 0, 3, 5, 7 and 10 years in desert steppe grassland in Yanchi County of Ningxia, to form a time series, for field and laboratory study of soil C dynamics. Variables measured included: total soil organic carbon (SOC), soil particulate organic carbon, soil dissolved organic carbon and soil readily oxidizable organic carbon for 10 cm increments of soil depth to 40 cm at each site. The results revealed significant differences (P<0.05) in total organic carbon at 5-10 cm, 10-20 cm and 20-40 cm soil depth, linked to the number of years of grazing exclusion. The SOC content ranged from 2.24 g·kg^-1 to 4.52 g·kg^-1, and in general increased with increased enclosure time. Thus, values were higher in desert steppe grasslands of 7 and 10 years grazing exclusion. There were no significant effects of grazing exclusion on soil particulate organic carbon (P>0.05). The contents of soil dissolved organic carbon were highest in grazed grassland (0.59, 0.49 and 0.56 g·kg^-1, respectively, for 0-5 cm, 5-10 cm and 20-40 cm soil depths). Values decreased initially after grazing exclusion, (with lowest values recorded after 5-7 years), and then increased with longer duration of exclusion. The soil readily oxidizable organic carbon content was highest (2.48 g·kg^-1) in desert steppe grassland subject to 7 years grazing exclusion. In summary, 7 years is a recovery point in the process of natural restoration and succession of degraded desert steppe by grazing exclusion.