Effects of waterlogging onseed germination of three Mediterraneanoak species: Ecological implications

摘要

Soil water saturation during prolonged periods of time generates a negative impact on nearly allterrestrial plants. In Mediterranean woodlands, precipitation can be very abundant during the wetseason, inducing temporary soil waterlogging, coinciding with the seed dispersal and germination timeof many species. We investigated the effects of waterlogging on seed germination and early root growthof three coexisting oak species (Quercus canariensis, Q suber and Q pyrenaica), by completely flooding ofseeds for various periods of time. The three oak species showed a certain level of tolerance to water-logging, only being affected those seeds subjected for long periods of submersion (over 30 days).Waterlogging during prolonged periods of time decreased the probability of seed germination in thethree oak species, lengthened the time to germination, and hampered root development in two of thestudied species. The main differences between oak species occurred in terms of root growth (Q canar-iensis being the less affected, and Q suber the most); these differential responses could be related toa species rank of waterlogging tolerance. Thus inter-specific differences in germination responses towaterlogging could contribute to explain, at least partially, species habitat and distribution patternsacross landscapes. Seed mass also played an important role on different aspects of germination, thoughits relative importance varied as function of species and waterlogging treatment. The tolerance to stressinduced by waterlogging increased with seed mass, but only in the case of Q. canariensis.