引入土壤种子库对铅锌尾矿废弃地植被恢复的作用

THE REVEGETATION OF A LEAD/ZINC MINE TAILINGS SITE WITH AN INTRODUCED SOIL SEED BANK

检测了丢荒旱作地土壤种子库，其种子含量为（６８５０±３７７）·ｍ－２，共有４１种植物。其中９２．７％的种和 ７５． ８％的种子是分布在 ０～２ ｃｍ的表层中。从丢荒旱作地采挖 １０ ｃｍ深的表层土壤，以 １ｃｍ， ２ ｃｍ， ４ ｃｍ和 ８ ｃｍ 等４种不同厚度分别铺放在铅锌矿尾矿废弃地试验小区上。尽管由于铺土厚度不同，各小区所含有的土壤种子库 中的种子数量也不同，但４种铺土处理试验，其幼苗平均数量分别为每平方米８８３± ４３４，９９５± １５８，１２４２± ３２７ 和８０３±３１株，经检验差异不显著，而不铺放表土的对照区则没有幼苗生长。可见，如果仅仅是作为提供种子资源 而引入土壤种子库，则铺放 １ｃｍ的表土就已足够。然而，经过１年以后，在铺放表土厚度为１ｃｍ， ２ ｃｍ和 ４ ｃｍ处 理上的幼苗全部死亡，只有铺放 ８ ｃｍ厚度表土的小区上实现了植被恢复，共有 １５种植物成功定居，其中有 １１种开 花结果，盖度达１００％。这说明了较薄的表土不足以有效阻隔尾矿与大气的接触，减缓酸化，以及缓冲尾矿酸化的影 响，此外较薄的表土也无法提供植物根系足够的生长空间。因此，如能预先铺放一层阻隔层，如底土、馀坭、垃圾之 类。

The size of the soil seed bank of abandoned farmland, intended for use in the revegetation of a lead/ zinc mine tailings pond, is investigated. The upper layer (0- 10 cm) of this farmland soil contained 6850 377 seeds. m 2 of 41 species. 75. 8% of all seeds counted and 92. 7% of the species found occurred in the top 2 cm layer. Topsoil from abandoned farmland was scraped down to 10 cm depth and directly spread over tailings in 4 different thicknesses: 1 cm, 2 cm, 4 cm and 8 cm. Although both the volume of topsoil used for covering and the estimated seed load differed, there was no significant difference in seedling density among the treatments covered with 1 cm, 2 cm, 4 cm and 8 cm topsoil. Many seeds from treatments with more than 1 cm of topsoil were unable to emerge from the greater depths. Compared with the covering topsoil of 2 cm, 4 cm and 8 cm, the layer of 1 cm topsoil attained a similar effect in terms of providing sufficient seeds. However, the seedlings in plots covered with 1 cm, 2 cm and 4 cm of topsoil failed to establish within one year. After one year just 15 species were remaining in 8 cm deep treatment, of which 11 flowered and fruited. The more shallow topsoil treatments were unable to neutralize the sulfuric acid-produced from the oxidation of pyrites in the tailings which resulted in the reduction of pH to between 2. 4 and 2. 8.