Effect Of Precipitation Change On Life History Of Annual Plant Distributed Widely In Desert Region Of Central Asia

Annual plant is an important part of desert vegetation in Central Asia.With the increase of precipitation,the germination time of these species changed from the following spring to autumn in the same year and the following spring,and continued to grow,flowering and fruiting in the spring of next year.Annual plant is significantly affected by precipitation in Central Asia.In this paper,27 species of annual species distributed widely in the desert of Central Asia were used as the research materials.The effects of precipitation on seed germination and the life cycle characteristics of five plants with spring-/ autumn-germinating plants in 27 plants were studied by simulated precipitation control experiment.The response mechanism of plant life history characteristics to climate change was discussed.The main results were as follows:(1)With 27 annual plants,78% of these species could germinated in autumn.In the six simulated precipitation treatments,the percentage of species germinated in autumn were 41%(simulated natural precipitation),63%(field capacity),52%(water increased by 50%),44%(water increased by 30%),33%(water reduced by 30%)and 30%(water reduced by 50%),respectively.Among the 26 sowing species,there were 6 species(Lappula patula,Lepidium perfoliatum,Alyssum linifollum,Plantago minuta,Ceratocephallus testiculatus and Hypecoum erectum)were germinated in the autumn.In the case of simulate increased precipitation(field capacity,water increased by 50 and 30%),the germination time of L.patula,A.linifollum,L.perfoliatum and P.minuta were 7-12 days advanced than control(simulated natural precipitation).Under the simulate reduced precipitation(water reduced by 30 and 50%),the germination time of three species(L.perfoliatum,L.patula and A.linifollum)was delayed by 24 days compared with control.(2)In the case of increased precipitation in autumn,the seeds of L.perfoliatum,A.linifollum,P.minuta,C.testiculatus and L.patula were germinated in the autumn of the current year and the spring of the following year,and form of the autumn-and spring-germination plants.The differences of germination time caused by precipitation variability had a significant effect on life cycles,flowering date,fruiting date,flowering period and fruiting period.Among them,life cycles of autumn-germinating plants were 3-4 times longer than ones in spring-germination plants.However,the reproductive growth time of spring-germinating plants was longer than that of autumn-germinating plants.The plants height,number of branches,leaves and biomass were significantly higher in autumn-than spring-germination plants.Reproductive output of autumn-germinating plants were 2.4-6.2 times bigger than in spring-germination plants.Biomass accumulation ratio of reproductive organs in autumn-germinating plants were higher than spring-germinating plants.The results indicated that: In the context of climate change these annuals behaved as facultative winter annuals in the Central Asian desert,rather than the early spring ephemeral plants reported by others.Under the precipitation increased,germination of species increased,and the germination time in advance.Under the precipitation reduced,germination of species decreased,and the germination time delayed.The difference of germination time was caused by precipitation climate,and there were significant differences in phenology,vegetative growth and reproductive growth.The life cycle,plant size,reproductive yield and seed size of autumn-germinating plants were significantly better than spring-germinating plants,thereby improving the offspring fitness and resistance.