封育对宁夏荒漠草原土壤有机碳矿化的影响

Effects of enclosure on soil organic carbon mineralization of desert steppe in Ningxia

以空间梯度代替时间梯度,在宁夏盐池县选择未封育及封育3、5、8、11 a的荒漠草原为研究样地,采用室内恒温培养的方法,测定不同封育年限草地土壤有机碳矿化潜力。结果表明,草地土壤有机碳累积矿化量随封育年限的延长总体呈增加趋势,表现为封育11 a草地>封育8 a草地>封育5 a草地>未封育草地>封育3 a草地。不同封育年限草地土壤有机碳矿化速率均以培养初期最大,随培养时间的延长迅速下降,但从第7天开始略有上升,第13天时又达到较高水平,之后开始逐渐下降,至第27天趋于平稳。不同封育年限草地土壤潜在矿化碳库(C_0)由高到低为封育11 a草地>封育8 a草地>未封育草地>封育5 a草地>封育3 a草地。封育8 a的草地土壤半衰期最短,显著(P<0.05)低于其他封育年限及未封育草地。因此,根据土壤有机碳矿化特征以及植被恢复状况,对封育5 a左右的宁夏荒漠草原可考虑适度利用。

In the present study, grazing grassland and grassland enclosed for 3, 5 , 8 , 11 a of desert steppe were se-lected as study objects in Yanchi County, Ningxia Province, to study the soil organic carbon mineralization potential by indoor constant temperature incubation. It was shown that with the increase of enclosing year, the accumulative soil organic carbon mineralization showed an increasing trend as 11 a enclosed grassland 〉8 a enclosed grassland 〉5 a enclosed grassland 〉 grazing grassland 〉 3 a enclosed grassland. From the 1st day to the 7th day, the mineralization rates decreased rapidly. From the 7th day to the 13th day, the rates rose slowly. Then, the rates decreased until the 27th day to be stable. With different enclosing year, the amount of potential mineralization carbon pools （CO） of the grassland decreased in sequence of 11 a enclosed grassland 〉 8 a enclosed grassland 〉 grazing grassland 〉 5 a en-closed grassland 〉 3 a enclosed grassland. The soil half-life of 8 a enclosed grassland was significantly （P 〈 0. 05 ） lower than others. Therefore, according to the soil organic carbon mineralization characteristics and the situation of vegetation restored, the grassland could be appropriately used after enclosing for 5 years.