Factors restricting seed germination and seedling recruitment of Ammopiptanthus mongolicus: an evergreen shrub endemic to cold deserts in China

摘要

Knowledge of abiotic and biotic stress regulating seedling recruitment of desert shrubs is limited. Using a combination of laboratory and field experiments, we determined (1) the interactive effect of soil moisture and temperature on seed germination; (2) the effect of burial depth on seedling emergence and seed survival; and (3) the effect of simulated seedling herbivory on seedling establishment of Ammopiptanthus mongolicus, an endangered evergreen shrub of the cold deserts of northwest China. Low water potential inhibited germination and increased seed death more at high than at low temperatures. No seeds sown on the soil surface germinated, whereas 52 and 34% of those buried in soil at 20 and 50 mm soil depth, respectively, did germinate. Most seeds sown on the soil surface died, whereas seeds buried 50 mm deep germinated but the seedlings subsequently died. A small portion of seeds was viable after 1.5 years burial on the surface in the field; thus, A. mongolicus can form at least a short-lived persistent seed bank. Seed predation had no effect on seedling emergence, whereas it significantly reduced seedling survival. Seedling biomass, height and survival rate decreased significantly as cotyledon removal ratio increased. These results may have potential value for conservation and restoration of A. mongolicus in its cold desert habitat.