Effect Of Precipitation Change On Germination Plasticity And Life History Of Annual Ephemerals

Annual ephemerals are a specific class in the Junggar Desert,which are ideal materials to study the responses of vegetation in the arid area to precipitation change.Focusing on the scientific questions with the effect of precipitation change on life history of terrestrial plants,we took annuals in Junggar Desert as research materials.By specimen/literatures,species investigation,and simulative autumn precipitation and spring extreme precipitation,effects of precipitation change on germination plasticity and consequences of autumn precipitation increasing and spring extreme precipitation on life history of annuals were studied,respectively.Our aims are to provide a theoretical basis for exploring the strategies of adaptation of annual ephemerals in Central Asia to precipitation change.The main results were described as follows:(1)There are a total of 21 families,86 genus and 147 species of annual ephemerals in the Northern Xinjiang,in which has 15 families,47 genus and 63 species of annual ephemerals germinated in autumn with precipitation increasing,which accounts for about 43%of the total annual ephemeral plants.And Zygophyllum lehmannianum and Erodium oxyrrhynchum could germinate in spring,summer and autumn.It showed that seed germination time of annual ephemerals in the Northern Xinjiang depended on precipitation,and most of annual ephemerals belonged to facultative winter annuals,not spring annuals which reported by previous studies.(2)Seeds of three species Lepidium perfoliatum,Plantago minuta and Ceratocephalus testiculatus in autumn precipitation increasing germinated earlier and plants were earlier to flower and fruit,but they were later to whither than control.It significantly prolonged the duration of flowering and fruiting of three species under the treatment of watering.And the plant height,number of branches,number of leaves,fruit biomass and plant biomass were significantly higher than control.With autumn precipitation increasing,there are some significant differences in life history of plants with waterd and no-watered.The differences could influence the breeding production and increase the number of seed bank and seed fitness.(3)In the simulative experiment of spring extreme precipitation,plants with watering on the first flowering date significantly extended the flowering period of spring-germinating plants(SP)and autumn-germinating plants(AP)and fruiting period of SP in Alyssum linifolium and Erodium oxyrrhynchum than natural precipitation.On the morphological characteristics,with watering on the first flowering date,there was an obvious increasing tendency in the plant height,number of branches and leaves of AP and number of branches of SP in A.linifolium,and number of branches and leaves of AP were increased obviously in E.oxyrrhynchum under the treatment of vegetative growth period.Also,there were some significant differences in plant height,number of branches and leaves of AP and SP under the treatment at same stage.Simultaneously,plants with watering on the first flowering date increased the reproductive biomass,and there were significant differences on fruit mass,seed mass and mass of 100 seeds under the same treatment.With spring extreme precipitation increasing,the life pattern of annual ephemerals would change and might have an effect on population and community characteristics.