腾格里沙漠东南缘苔藓结皮对荒漠土壤种子库的影响

Effects of moss crust on soil seed bank at southeast edge of Tengger Desert

对腾格里沙漠东南缘沙坡头人工植被区和天然植被区苔藓结皮种子库进行了研究.结果表明,土壤种子库密度随着苔藓结皮的发育呈现增加的趋势,天然植被区是24年生人工植被区的3.4倍.种子库中共发现12种植物种子,分属于6科,其中1年生草本植物占70%以上.人工植被区未发现有多年生草本的植物种子,天然植被区多年生草本占20%,半灌木植物在人工植被区和天然植被区分别占20%和10%.人工植被区土壤种子库物种丰富度指数相对较低,而天然植被区物种丰富度指数是人工植被区的2倍;人工植被区土壤种子库物种多样性指数随着结皮的发育略有下降,天然植被区的多样性指数最高,为0.693;人工植被区土壤种子库物种相似性指数为1,相对较高,而人工植物区与天然植被区的物种相似性指数为0.4.苔藓结皮的出现增加了地表粗糙度,有利于对种子的捕获,同时显著地改善了土壤环境,有利于更多植物的定居.

An investigation was made on the soil seed bank at southeast edge of Tengger Desert with moss crust under natural and artificial vegetations. The results showed that the density of soil seed bank increased with the development of moss crust, which was 3.4 times higher under natural vegetation than under 24 years old artificial vegetation. In the seed bank, a total of 12 species belonging to 6 families were identified, among which, annuals occupied more than 70%. No perennial seeds were found under artificial vegetation, but under natural vegetation, 20% of the seeds were of perennials. As for semi-shrub seeds, they occupied 20% and 10% under artificial and natural vegetation, respectively. Under artificial vegetation, the species richness index of soil seed bank was relatively lower, being about a half of that under natural vegetation. The species diversity index of the seed bank had a slight decrease with the development of moss crust under artificial vegetation, but increased to the maximum （0. 693 ） under natural vegetation. The species similarity index was 1 among the seed banks under artificial vegetations, and 0.4 between those under artificial and natural vegetation. The development of moss crust increased the roughness of surface soil and improved soil environment significantly, which could have positive effects on seed entrapment and plant establishment.