土壤种子库在黄土高原本氏针茅草地群落长期封禁演替过程中的作用

The role of soil seed bank in vegetation succession under grazing exclusion in Stipa bungeana grasslands on the Loess Plateau

地上植被与土壤种子库的耦合研究对于探索退化草地在长期封禁过程中的演替过程及其机理具有重要意义。采用除趋势对应分析(DCA)对黄土高原典型草原本氏针茅群落进行地上/地下演替梯度分析;利用非加权组平均(UPGMA)聚类分析对土壤种子库与地上植被的相似性进行数量生态学分析。结果表明,随着封禁年限的延长,本氏针茅群落经历了以下几个演替阶段:杂草群聚生长阶段→本氏针茅大量出现→本氏针茅稳定发展阶段。在整个演替过程中,地上植被有明显的顺向演替趋势,但是土壤种子库之间未能表现出明显差异。地上植被演替阶段影响土壤种子库与地上植被的关系,演替初期地上植被与土壤种子库的相似性高于演替后期的二者相似性,说明土壤种子库在演替初期对地上植被的贡献比较大。因此,推动地上植被演替的内部驱动力不是土壤种子库,而是繁殖体散布和无性繁殖。

Understanding the coupling effect on above-and below-ground species composition was important for exploring the succession process and its mechanism of degraded grasslands under grazing exclusion.The study respectively made the succession gradient analysis on vegetation and soil seed bank using detrended correspondence analysis（DCA） and unweighted pair-group method with arithmetic means（UPGMA） cluster analysis on the relationship between vegetation and soil seed bank in Stipa bungeana grasslands on the Loess Plateau.The results indicated that with grazing exclusion years increasing,S.bungeana grasslands had the following succession stages： the cluster growth of weeds→S.bungeana emerging in large numbers→the stable development of S.bungeana.The vegetation succession showed a clear positive direction,however,no clear trend in soil seed bank.The vegetation succession stages influenced the relationship between vegetation and soil seed bank.The similarity between vegetation and soil seed bank in early succession was higher than late-succession stages,indicating soil seed bank made a relatively larger contribution to vegetation restoration in early-succession stages.Overall,soil seed bank played a minimal role in the process of vegetation succession under the grazing exclusion in S.bungeana grasslands.Therefore,the internal driving forces of vegetation succession under grazing exclusion in typical steppe were propagule dispersal and asexual reproduction,not soil seed bank.