围封对沙漠化草地土壤理化性质和固碳潜力恢复的影响

过度放牧是科尔沁沙地退化的主要原因，禁牧围封可以有效地控制牲畜对植被-土壤系统的破坏，促进退化生态系统的有效恢复。以过度放牧后的沙漠化草地为对象，调查了禁牧围封13年后沙漠化草地土壤理化性质的变化特征，并分析了围封对土壤固碳潜力的影响。结果表明：（1）沙漠化草地围封13年后，土壤砂粒含量减少、粉粒和黏粒含量增加，且粉粒增加最为明显，平均含量增加123%；土壤容重在不同土壤深度均呈下降趋势。（2）围封后土壤有机质、全氮、速效氮和速效钾含量呈增加趋势，分别增加了102%、97%、123%和24%，但土壤有效磷和缓效钾呈减少趋势；土壤pH显著升高，阳离子交换量呈现增加趋势。（3）除土壤有效铁外，其余有效微量元素包括有效铜、有效锰和有效锌平均含量均呈增加趋势，分别增加44%、30%和82%。（4）土壤有机质与pH值、阳离子交换量、全氮、速效氮、速效钾、有效铜、有效锰、有效锌含量呈显著正相关关系。（5）沙漠化草地围封13年后，100 cm深度土壤有机碳储量增加393.45 g·m^-2，碳截存速率为30.27 gC·m^-2·a^-1。对于因持续过度放牧所导致的严重退化草地，禁牧围封可有效促进土壤有机质、养分和微量元素的增加，影响土壤质地及固碳潜力等的变化，但严重退化沙漠化草地的恢复需要一个长期的过程，土壤有机碳储量要恢复到科尔沁非沙漠化草地水平至少需要百年的时间尺度。

Effects of Exclosure on Soil Physicochemical Properties and Carbon Sequestration Potential Recovery of Desertified Grassland

Heaving grazing is regarded as one of the main reasons of soil degradation and desertification in the semiarid Horqin sandy grassland of northeastern China. Exclosure can control the destruction of livestock to vegetation-soil system effectively and contribute to improve the restoration of degraded ecological system. Desertified grassland, which was overgrazing, was taken as control for objection. Soil physicochemical properties were examined and analyzed the effect of exclosure on carbon sequestration potential under continuous grazing and exclusion of livestock for 13 years in desertified grassland. It was found that, after exclosure for 13 years, it had lower sand contents and higher silt and clay contents at all depths, especially for silt, which increased by 123%. The soil bulk density was lower at all five depths. Mean soil organic matter, total nitrogen, available N, available K contents increased by 102%, 97%, 123% and 24%, respectively, while available P and slowly available K went down. Soil pH increased significantly. Cation exchange capacity (CEC) went up. Except for available Fe, the mean available Cu, Mn and Zn increased by 44%, 30% and 82%, respectively. Soil organic matter was significantly positively correlated with total N, pH, CEC, available N, K, Cu, Mn, Zn (P<0.05). To a depth of 100 cm, soil carbon stock increased 393.45 g·m^-2 and carbon sequestration rate was 30.27 g C·m^-2·a^-1 after exclosure of desertified grassland for 13 years. The research shows that livestock exclusion can improve soil organic matter, nutrients and microelements and the change of soil texture and carbon sequestration potential. While the recovery of serious desertified grassland needs a long process to be raised, carbon stock is needed to restore the non-desertified grassland standard at least centenary temporal scale.