Hybridization And Seed Dispersal Of Three Quercus Species In Beijing Area

Regeneration is an important process for forest plants to maintain population continuity and community stability.The problem which influence population regeneration of oaks has been research hotspot both here and abroad,such as hybridization and seed dispersal.Q.aliena,Q.dentata and Q.variabilis,are main native tree species in Beijing area.It is of great ecological value to understand their regeneration.Phenological monitoring of three Quercus species was conducted in Shangfang Mountain National Forest Park from March to October 2018 and Jiufeng National Forest Park from March to October 2019 in Beijing area.Phenological changes were frequent during the bud stage and flowering stage.So observation was conducted once every 2-3 days.Once a week during ripening stage.And once two weeks during other period.It was found that there was a phenological overlap inflowering between three Quercus species.The flowering period overlaps at least 11 days in 2018,and 4 days in 2019.Hybridization experiment between three Quercus species was conducted in Shangfang Mountain from April to May 2018 and in Jiufeng Mountain from April and May 2019.Since male flowers appeared,I observed the growth of flowers every day.There were 262 cross pollination bags in Shangfang Mountain.The results showed that artificial pollination enabled three Quercus species to overcome the pre-fertilization barrier and successfully mate.But a large number of embryo abortion occurred later.Finally 3sterile seeds were left.Thus no fertile offspring were produced.There were 591 cross pollination bags in Jiufeng Mountain.Similar to the results in2018,hybrid fruit dropped a lot after pollination.Only 1 sterile seed was produced.Two experiments showed that the crossbreeding was affected by both pre-fertilization andpost-fertilization barriers,so the success rate of hybridization was low.From October 2018 to March 2019,seed dispersal experiment of three kind of oaks was carried out in Shangfang Mountain.6 plots and 1800 seeds were used in this experiment.First,placed seeds in site;second,recorded the whole process of seed dispersal by infrared camera;finally tracked the fate of seeds.The order of seed been chosen by rodents and seed fate,combined with physical and chemical traits of seeds,were used to study the selection strategies of rodents for seed food.It was found that the preference of rodents for seed was mainly affected by size and husk thickness of seeds.Rodents prefer to eat seeds of Q.dentata which are small-sized,thin-skinned in situ.The following is seeds of Q.aliena with middle size and husk thickness.But they store Q.variabilis with large seeds and thick husk.This may be the final choice of rodents' overall consideration of nutritional value,predation risk,benefit of a single seed and other factors.This study provides scientific theoretical support for the protection and utilization of regeneration of oaks,and provides reference for the studies on the breeding and diffusion of different species sympatricly.