丹江口库区滩涂与入库支流植被与土壤种子库:水传播潜力探讨

Comparison of the established vegetation and soil seed bank of tidal flat versus tributary habitats of China’s Danjiangkou Reservoir: the potential of hydrochory

为了探索库区滩涂与入库支流土壤种子库与植被的关系,以及物种通过水传播扩散的潜力,对丹江口库区内4条支流及其入库滩涂的地表植被和土壤种子库进行了调查。结果显示,支流地表植被和种子库的物种多样性高于库区滩涂,汉江库区滩涂和支流的地表植被与种子库均有较高的物种相似性。DCA排序和TWINSPAN聚类可以明显地将支流的植被和种子库样方与滩涂的植被和种子库样方分到不同的样方组,结合物种排序图可以清楚地发现,流入汉江库区支流的植被和种子库的物种组成与滩涂的植被和种子库的物种组成有密切联系。汉江库区滩涂0–15cm的土层内都有种子萌发,而丹江库区种子库中只有狗牙根(Cynodon dactylon)一种植物,且仅存在于0–5cm土层。研究结果表明,繁殖体通过支流向滩涂的水传播作用对植被建立有积极贡献。

Aims Our objectives were to compare the established vegetation and soil seed bank of tidal flat and tributary habitats of the Danjiangkou Reservoir of China’s Han River and to identify the contribution of hydrochory （dispersal of seeds by water） from the tributaries to the reservoir tidal flats. Methods We sampled the vegetation and soil seed banks of four tributaries and the reservoir tidal flats of their estuaries. Using data from 91 sample plots, we compared the species composition of the established vegetation and soil seed banks of the tributaries and their tidal flats using S？rensen’s coefficient of similarity, detrended correspondence analysis （DCA） and two way indicator species analysis （TWINSPAN）. Important findings Species richness of the established vegetation and seed bank along the tributaries was considerably higher than in the reservoir tidal flats, but the density of seedlings germinated from the soil seed bank was not significantly different between the two habitats. TWINSPAN and DCA showed a separation of sites from the tributary and tidal flat zones. In the DCA ordination diagram, however, most species were grouped between the tributaries and tidal flats, indicating a close relationship of species composition between the two habitats. S？rensen’s coefficient of similarity also revealed a high similarity of the established vegetation and seed bank between the tributaries and the tidal flats. Seeds were germinated from all three layers of the top soil （0–15 cm） in the Han reservoir tidal flats, while only one species, Cynodon dactylon, was found in the top soil of 0–5 cm in the Dan Reservoir tidal flats. Our results indicate a potential contribution of hydrochory from the tributaries to the vegetation of the reservoir tidal flats.