蒿类荒漠草地土壤种子库特征及其萌发植物多样性对降水增加的响应

为揭示土壤种子库种子萌发对降水增加的适应规律,采用人工模拟降水方法,对不同降水量[对照(CK)、增加5% (W₅)、增加10% (W₁₀)、增加15% (W₁₅)、增加20% (W₂₀)、增加25% (W₂₅)]下中度退化伊犁绢蒿荒漠土壤可萌发种子库种子萌发数量及其多样性进行了调测。结果表明:0~5 cm土层土壤种子库萌发物种数及其萌发总密度随降水量增加呈上升趋势,且W₂₀、W₂₅下萌发密度显著高于其他处理(P<0.05),萌发物种数较对照(7种)依次增加2.6、2.0倍;5~10 cm土层也呈现相同的变化趋势。无论降水增加与否,0~10 cm土层伊犁绢蒿、木地肤、毛梗顶冰花均有萌发,且降水增加显著促进伊犁绢蒿、木地肤、串珠老鹳草、毛梗顶冰花的萌发。随降水量增加,0~5 cm土层伊犁绢蒿可萌发土壤种子库与地上植被Sorensen相似性总体呈先增后降趋势,且降水增加≥20%处理相似性高于降水增加≤15%处理。降水增加后伊犁绢蒿荒漠土壤种子萌发物种的Shannon-Wiener指数、Pielou指数、Patrick指数总体呈增加趋势,且0~5 cm土层较5~10 cm土层增加明显。土壤种子库可萌发种子密度具明显的空间异质性,且受空间取样位置及降水的交互影响。综上所述,降水增加促进了伊犁绢蒿荒漠草地土壤种子库可萌发植物种数、种子萌发密度、植物多样性指数的增加,导致其与地上植被的相似性增加,有利于退化蒿类荒漠草地的恢复。

Response to increasing precipitation in Artemisia desert grassland of soil seed bank composition and species diversity of germinating plants

In this study, plots of six different precipitation regimes [natural conditions, CK; and artificially simulated precipitation increases of 5% (W₅), 10% (W₁₀), 15% (W₁₅), 20% (W₂₀) and 25% (W₂₅)] were established in moderately degraded Seriphidium transiliense desert grassland in order to study the effects of increasing precipitation on the seed density in the soil seed bank and on numbers of plant species represented. It was found that the number of species with germinated seedlings, and the seed numbers in the soil seed bank in the 0-5 cm soil layer increased gradually with increasing precipitation, with the germinated-seedling density of W₂₀ and W₂₅ being significantly (P<0.05) higher than other treatments, and the number of species with germinated seeds increased by 2.6 times and 2.0 times respectively as compared with the CK treatment (7 species). The same pattern was also seen in the seed bank of the 5-10 cm soil layer. For all six precipitation regimes, S. transiliense, Kochia prostrata and Gagea albertii all germinated in soil from the 0-10 cm soil layer, and precipitation increase significantly promoted the seed numbers germinated of S. transiliense, K. prostrata, Geranium transversale and Geranium albertii. With increasing precipitation, the Sorensen similarity between species germinating from the soil seed bank in the 0-5 cm soil layer and aboveground vegetation increased first and then decreased in S. transiliense desert grassland, and the Sorensen similarity of species composition of aboveground vegetation under W₂₀ and W₂₅ treatment was higher than other treatments. The Shannon-Wiener index, Pielou index and Patrick index of the number of species represented in the seedbank in S. transiliense desert grassland showed an increasing trend after precipitation enhancement, and the increase in the 0-5 cm soil layer was more obvious than that in the 5-10 cm soil layer. The germinated seed density in soil seed bank had obvious spatial heterogeneity, and was affected by the interaction of spatial sampling locations and precipitation. In summary, precipitation enhancement increased the number of germinating plant species, the density of seeds germinating, and the plant diversity index in the soil seed bank of the S. transiliense desert grassland studied. This in turn increased the similarity in species composition between the aboveground vegetation and the seedbank and was beneficial to the restoration of degraded sagebrush desert grassland.