春季休牧对内蒙古羊草草原有机碳储量的影响

为了揭示休牧对羊草草原有机碳储量的影响，以休牧3年（RG3a）、6年（RG6a）和9年（RG9a）的羊草草原为对象，采用重铬酸一浓硫酸外加热法，研究了不同休牧年限草原植物群落和土壤的有机碳储量变化。结果表明，地上植被生物量、凋落物量和根系生物量随着休牧年限的延长而逐渐增加。与长期自由放牧草地相比，植物群落和土壤有机碳储量均随休牧年限的延长而增多。长期自由放牧草地（RG0）、休牧3年、休牧6年和休牧9年植物群落地上部有机碳储量为65．17～98．69gC·m^-2，地表凋落物有机碳储量为3．07～10．84gC·m^-2；植物群落0～100cm地下根系有机碳储量为397．13～1480．28gC·m^-2,0～100cm土壤有机碳储量为28306．39～38372．46gC·m^-2。从固碳成本角度，总固碳成本随着休牧年限的延长而增加，最高为8710．20元·hm^-2，固碳成本分别为0．09、0．11、0．08元·kg^-1C。从现有数据显示，休牧9年的固碳量最高，固碳成本最低。春季休牧可以使草地植被得到有效的恢复与更新，有利于草地的可持续利用；随休牧年限的增加，草地有机碳储量增加，固碳成本基本呈现降低趋势。因此，综合现有指标的测定数据，春季休牧是一个非常好的草地利用措施，在休牧过程中草地是一个碳汇，应该鼓励持续进行。

Effects of Spring Rest Grazing on Organic Carbon Storage in Leymus Chinensis Steppe in Inner Mongolia, China

Rest grazing is an important means to maintain the sustainability of grassland ecosystems. To evaluate the potential effects of rest grazing on organic carbon storage in the Leymus chinensis Steppe, organic carbon storage in plant and soil was compared in the steppes with different rest grazing durations （3 years--RG3a, 6 years--RG6a, and 9 years--RG9a） using long-period free choice grazing （RG0） as the control. Compared with long-period free choice grazing, biomass of aboveground, litter and underground parts of plants, and organic carbon storages in plant communities and soils increased with increased rest grazing durations. Total cost of carbon sequestration increased as years of rest grazing increased, with up to 8 710.20 Yuan（RMB）.hm-2, while the unit cost reduced. Considering the growth characteristics of grassland plants, the spring season should be free of grazing. Timely rest grazing could restore and renew grassland vegetation.