云雾山不同草地群落土壤活性有机碳分布特征

Distribution Characteristics of Soil Labile Organic Carbon of Different Grassland Communities in Yunwu Mountain

为探讨黄土高原草地植被演替过程活性有机碳的变化规律，揭示草地退耕后的分布特征，在云雾山草原区采集不同草地群落土壤，采用高锰酸钾氧化法对0～100 cm土层活性有机碳进行分析。结果表明：不同草地群落土壤活性有机碳含量均高于坡耕地，活性有机碳含量大小顺序为：长芒草（Stipa bungeana Trin．）群落〉大针茅（Stipa grandis P．Smirn．）群落〉铁杆蒿（Arternisia gmelinii Web．ex Stechm．）群落〉百里香（Thymus mongolicus Ronn．）群落〉退耕草地〉坡耕地，且群落间差异达极显著水平（P〈0．01）；在恢复初期（坡耕地-退耕草地-百里香）活性有机碳含量增加较多，恢复到长芒草群落活性有机碳含量达到最大值，趋于稳定；活性有机碳的密度与含量表现出相同的变化规律，并随着土层的加深而呈现减小趋势。相关性分析表明，活性有机碳含量与土壤总有机碳含量呈极显著线性正相关关系（r=0．9742），土壤活性有机碳比总有机碳更能反映草地植被恢复初期土壤有机碳库的变化。

Returning the slope farmland to grassland is the best approach to improve soil quality and soil fertility through its influence on the accumulation and fixation of soil organic carbon. We analyzed the content of soil labile organic carbon （LOC） from soil depth 0 to 100 cm of different grassland communities in Yunwu Mountain using potassium permanganate oxidation method. The results show that soil LOC content of different vegetation communities was significantly higher than that of slop farmland （P〈0.01）which followed the order of Stipa bungeana Trin. community〉Stipa grandis P. Smirn. community〉Artemisia gmelinii Web. ex Stechm. community〉Thymusmongolicus Ronn. community〉returned grassland〉slop farmland; there was a significant difference among different grassland communities. Furthermore, soil LOC content increased largely in the initial recovery stage （slope farmland-returned grassland-T, mongolicus community） while it reached to the maximum for S. bungeana community. Dynamics of soil LOC density was similar to LOC content among different vegetation communities and showed a decreasing trend along with the increase of soil depth. The linearly significant positive correlation （r=0. 9742） was found between soil LOC content and soil total organic carbon. Soil LOC content could be a better parameter to reflect the status of soil organic carbon pool during early grassland recovery stage than soil total organic carbon content.