Variation in Soil Seed Banks Composition at the Desert Microhabitats of Caragana korshinskii Shrubs

摘要

The species composition of the soil seed banks and their distribution in the revegetated desert ecosystems were studied with the seedling emergence method around re-established Caragana korshinskii shrubs by comparing these with that of natural C. korshinskii shrubs patches, which grow under identical bioclimatic conditions. The results indicated that there were significant differences in the soil seed banks composition among the microhabitats in both areas, while the orientation effects were detected at the revegetated site, where the wind plays an important role in structuring the soil seed banks. There were more forb seeds in southeastern and southwestern directions of the C. korshinskii shrubs than in the northwest and northeast, and their abundance decreased from microhabitats under the shrub canopies, to the shrub edges, and to the intercanopy spaces. The grass seeds, by contrast, were most abundant at the intercanopy spaces, intermediate at the edges of the shrub canopies, and lowest at the centre of the patch under the shrub canopies. There was high seed density heterogeneity within the four microhabitat classes of the orientation from the revegetated shrub patches. Differences between microhabitats were greatest in the revegetated site and tended to disappear in the natural site. Seed densities in the natural site were around 3.6 times greater than in the revegetated site, this difference was mainly accounted for by the annual forbs and grasses in the natural site and suggests that for the desert ecosystems restoration will be a long-term process in terms of the spatial soil seed banks variation.