河西走廊荒漠绿洲过渡带封育对土壤和植被的影响

在河西走廊荒漠绿洲过渡带,封育天然植被是植被群落恢复、防止绿洲沙漠化的有效措施。以流动沙丘作为对照(0年),对封育5年和15年的半固沙和固定沙丘植被群落以及土壤进行调查取样和分析。结果表明:随着封育年限增加,天然固沙植被群落生物多样性增加,灌木层和草本层植物密度、盖度和生物量都显著增加,灌木层盖度从10%增加到40%,草本层以一年生草本植物为主,物种从5种增加到8种,生物量从1 g·m^-2增加到13 g·m^-2。随着天然植被盖度增加,土壤表层沙土细粒化明显,沙土中黏粉粒含量显著增加,土壤质地由粗质沙粒向细质沙粒转变;随着沙土中黏粉粒成分的增加,沙土有机质、全氮、全磷含量也增加,灌丛下土壤养分含量高于灌丛间,“沃岛效应”明显。同时,在灌丛下表层土壤出现明显的盐分集聚现象,其中SO₄^2-、K⁺、Na⁺含量分别增加了6、3、17倍。在降水100 mm左右的荒漠绿洲过渡带,封育可以显著恢复固沙植被群落和提高沙土质地和养分。

The changes of soil physical and chemical property during the enclosure process in a typical desert oasis ecotone of the Hexi Corridor in northwestern China

In the desert oasis ecotone of the Hexi Corridor, enclosing natural vegetation is one of the most economical measures to restore vegetation communities and prevent desertification in oasis. In this paper, we used mobile sand dunes as a control (0 years) and investigated the changes in soil and vegetation after 5 and 15 years enclosing in desertifed land. The results showed that the biodiversity of natural sand-fixing vegetation community increased, and the density, coverage and biomass of shrub layer and annual herbaceous plant layer also increased significantly.The shrub layer coverage increased from 10% in shifting dunes to 40% in stabilized dunes after 15 years of enclosure. The herbaceous plant layer was dominated by annual herbaceous species, and the biomass increased from 1 g·m^-2 to 13 g·m^-2. With the increase of natural vegetation cover, the content of clay and silt significantly increased and the soil texture was changed from coarse sand to fine sand. The organic matter, total nitrogen and total phosphorus also increased, and the soil nutrients content under the shrub was much higher than in the alley. However, there was a significant accumulation of salt occurred in the soil surface, and the irons such as SO₄^2-, K⁺ and Na⁺ increased by 5, 2 and 16 times, respectively. In the arid desert oasis ecotone with precipitation of about 100 mm, the enclosure can restore the sand-fixing vegetation community and improve the sandy soil texture and nutrients. However, the soil salinity needs further investigation in future.