Species shifts in above-ground vegetation and the soil seed bank in the inter-dune lowlands of an active dune field in Inner Mongolia, China

摘要

Degradation of semi-arid ecosystems leading to desertification presents a global environmental challenge. However, few studies have investigated seed bank and above-ground species composition in degraded semi-arid dune systems, particularly in relation to their potential to contribute to stabilisation and revegetation. We determined whether soil seed bank and above-ground species composition differed along a chronosequence in the inter-dune lowlands of an active dune field in Inner Mongolia, China. Soil cores were collected in early April 2011 and soil seed bank composition determined using a combination of the seedling emergence and seed extraction methods. Established vegetation, including species composition and abundance, was also surveyed. Relative importance values for all above-ground species and similarities in species composition of vegetation and soil seed bank along the chronosequence were analysed. A clear successional trend was shown for established vegetation along the first three stages identified, followed by a final stage reverting to more mobile substrate due to disturbance by dune movement. This trend was not reflected in the seed bank. Plant and seed bank density increased over time, however, species composition of the seed bank reflected earlier stages rather than the corresponding established vegetation. There was a relationship between established vegetation and the soil seed bank at the earliest stage, driven mainly by the persistence of seeds of the pioneer species Agriophyllum squarrosum and Corispermum candelabrum. A relatively close relationship was also found at the final stage, where frequent disturbance occurred as a result of increasing sand burial, caused by constant directional sand dune movement. While a clear relationship between the seed bank and associated vegetation was not found along the whole chronosequence, the seed bank displayed potential for restoration of pioneer psammophytes and annual herb species, suggesting that it would contribute to regeneration, as well as support latter-stage annuals and several rare and endemic species.