Effects Of Simulated Precipitation Patterns Changing On Seed Germination And Seedling Growth Of Reaumuria Soongorica

Global climate change is predicted to alter rainfall patterns of the growing season, potentially reducing total quantities of precipitation and redistributing rainfall into fewer but larger individual events. Such changes are likely to have profound effects on terrestrial ecosystems. Soil, plants, and even the function of ecosystem in arid and semi-arid regions of Northwest China would be affected, and this could ultimately affect species composition and biological diversity. Both the quantity and the time interval of precipitation will have an important influence seeds germination and seedling growth.Reaumuria soongorica is a typical species of the arid regions of Northwest China, the responses of R. soongorica seeds and seedlings to altered precipitation patterns could reflect the general responses of other plant species in this ecological system. So R. soongorica was used as the materials to study its seeds germination characteristics, seedlings growth traits, biomass accumulation and allocation, and root morphological characteristics under different precipitation patterns during the growing season at the continental river basin research station of Chinese ecosystem network in Linze. On the one hand, we hoped to find out the responses and adaptation mechanisms of seeds and seedlings to changing precipitation patterns, On the other hand, it may be able to provide a preliminary theoretical basis and scientific support to the update effects of desert plants in the future. A ventilated rainout shelter was used for experimental manipulation of rainfall patterns to keep temperature and CO2 close to natural conditions. Then we set up a controlled experiment with two variables: precipitation quantity and precipitation time interval. The three variations of precipitation quantity were-30%(W-); natural precipitation(W); and +30%(W+). The two precipitation time intervals were 5 days and 10 days. The results were as followings:(1) Germination period can be prolonged efficiently by extending precipitation time interval, effect was more significant when precipitation increased by 30%, not only delayed the end of seed emergence period, but also improved seeds germination rate significantly; All of the indexes: germination percentage, germination potential, germination index and vigor index fell, when precipitation decreased by 30%, but not significantly. Under the condition of precipitation increased by 30% and precipitation time interval extended to 10 days, the vigor index come up to the maximum, germination index increased by 57.67%, germination percentage and germination potential increased by 45.69% and 39.86% respectively(P<0.05). It showed that the big precipitation events caused by longer time interval and increased precipitation was more conducive to seeds germination.(2) The growth of aboveground parts was accelerated via precipitation increased by 30%, the height and base diameter of seedlings increased by an average of 22.0% and 28.0% respectively(P<0.05), aboveground biomass also increased by 241.57% significantly(P<0.05); The growth of aerial parts was slowed down when precipitation decreased by 30%, but root growth was not be suppressed, the root length meanly increased 21.0%, and the root/shoot ratio increased significantly by 53.73%(P<0.05).(3) Extending precipitation time interval in the same rainfall condition, root morphological indexes showed a trend of increasing, total root length, total root volume and root biomass respectively increased by 39.22%, 62.50% and 63.20% significantly(P<0.05); It presented a promoting effect to seedling root indexes under the condition of 10 days precipitation time interval and precipitation increased by 30%, and the effect was more prominent to the total root volume and root biomass, they respectively increased by 116.27% and 224.40% significantly(P<0.01).(4) Excepting SRL and SRA reached the maximum under the condition of natural precipitation and 10 days precipitation time interval, other indexes did not change significantly, it showed that the water absorbing efficiency of seeding root system reached the point under that treatment; Correlation analysis showed that there were different levels of correlation between different indexes in different precipitation patterns, total root length, total root superficial area, total root volume, average diameter and root biomass were significantly positive correlation with each other, and root biomass has very significant positive correlation with both root total surface area and total root volume. These results suggested that R. soongorica seedlings can adjust their water balance by root morphological remodeling, changing biomass allocation patterns, slowing down the growth of branches and leaves to adapt to different precipitation patterns, in order to insure the plant can grow and update normally.