Alternanthera philoxeroides invasion affects the soil seed bank of reed community.
Biological invasion is a global environmental problem that has profound effects on the natural ecosystem. To gain in-depth understandings on how biological invasion affects the natural recovery potential of native vegetation, this study focused on the soil seed banks of reed (Phragmites australis) communities with different degrees of Alternanthera philoxeroides invasion. The soil seed banks were germinated under three light conditions (shading, natural light and supplementary light) and three water level conditions (immersed, 3 cm water flooded and 30 cm water flooded). The effects of the different degrees of A. philoxeroides invasion, light conditions, and water levels on the soil seed bank germination of reed communities were compared and analyzed. Our studies revealed that A. philoxeroides invasion had remarkable impacts on the soil seed banks of wetland reed communities during less than three years and water level and light had interaction on the effect of invasion. Under the supplementary light treatment, the number of germinating species in the non invasive soil seed bank (average 3.78 species/box) was significantly higher than that in the seriously invasive soil seed bank (average 2.22 species/box)(N = 9, P ≤ 0.05). Under immersed treatments, A. philoxeroides invasion significantly reduced the seedling density from average 905 seedlings/m2 without invasion to average 363 seedlings/m2 with mild invasion and 313 seedlings/m2 with severe invasion, N = 9, P0.05 and the species richness (from average 4.33 species/box without invasion to average 3.11 species/box with mild invasion and 3.11 species/box with severe invasion, N = 9, P0.05) of reed community soil seed banks. Under 30 cm water flooded treatment, the dominance index of the soil seed bank with severe invasion was significantly higher than that with mild invasion. Shading and flooding inhibited the seed germination from soil seed bank. We also discovered that A. philoxeroides invasion reduced the seedling density of the light-requiring species and the terrestrial species, such as E. crusgalli, which finally impairing the natural seed recovery potential of reed communities. These findings showed new lights on the invasion plant management and the native vegetation restoration.