不同恢复措施对宁夏典型草原土壤碳氮储量的影响

Effects of different restoration measures on storage of soil organic carbon and nitrogen in typical steppe of the Loess Hilly Area in Ningxia

为探讨不同恢复措施下草原土壤有机碳、全氮储量特征的变化,以宁夏黄土丘陵区典型草原为对象,对放牧(对照GG),封育(EG),水平沟(CG)和鱼鳞坑(FG)3种不同恢复措施下0~40 cm土壤有机碳、全氮储量进行研究。研究表明:1)土壤有机碳和全氮含量以封育草地最高,分别为30.35和2.92 g/kg,放牧草地次之,水平沟草地最低(P<0.05);C/N表现为封育最高,水平沟次之,放牧草地最低;各措施下土壤有机碳和全氮含量随着土层加深整体呈下降趋势。2)土壤有机碳和全氮密度呈封育和放牧草地较高,鱼鳞坑居中,水平沟最低。各恢复措施下有机碳密度随着土层加深而降低,全氮密度无明显规律。3)土壤碳氮储量表现为封育草地>放牧草地>鱼鳞坑草地>水平沟草地。禁牧封育更有利于该区典型草原土壤有机碳和全氮储量的积累。

Land-use strongly influences soil properties such as soil organic carbon（ SOC） and total nitrogen（ TN）. This study has been done to investigate changes in grassland organic carbon and nitrogen storage characteristics under different restoration measures in typical steppe of the Loess Hilly area in Ningxia,which is located in the Yunwu hills（ longitude 106°21＇-106°27＇ E,latitude 36°10＇-36°17＇ N,altitude 1800-2100 m） and has a very steep slope（ approx.30-50°）. The annual mean temperature is 5 ℃,with a range from approx. 22-25 ℃ in summer（ July） to-14 ℃in winter（ January）. The annual precipitation is 445 mm,of which 60% occurs in autumn and is associated with storm events in the July-September period that sometimes cause runoff. The storage of organic carbon and nitrogen was measured in 0-10,10-20,20-30 and 30-40 cm soil layers for three different restoration measures,including grazed（control）,exclosure,contour trenches and fish-scale pits. Our results revealed that the content of SOC and TN were the highest in exclosure grassland（ 30. 35 and 2. 92 g/kg respectively）,followed by grazed,fish-scale pits and contour trenches（ P〈0. 05）. C/N was highest in exclosure grassland,in the middle in contour trenches and fish-scale pits,and the lowest in grazed grassland. The content of SOC and TN under the different restoration measures decreased with increasing soil depth except for the content of TN of 10-20 cm soil layer in contour trenches and fish-scale pits. However,soil depth did not have an effect on soil bulk density under the different measures. The density of SOC and TN was highest in exclosure and grazed grassland,in the middle in fish-scale pits and the lowest in contour trenches. Soil depth had an effect on the density of SOC under different restoration measures whereas it had no effect on the density of TN.The storage of both soil carbon and nitrogen decreased in the following order： exclosure 〉grazed 〉fish-scale pits〉 contour trenches. Organic carbon storage was highly significantly positively correlated with soil organic carbon and total nitrogen content; and nitrogen storage was significantly positively correlated with total nitrogen content.