Effects Of Day And Night Warming On Plant Reproductive Phenology In A Temperate Steppe Of Northern China

Since the industrial revolution,anthropogenic activities have led to global change,with consequent impacts on terrestrial ecosystems.Grasslands in China are sensitive to climate change.Understanding of individual plants in response to climate change is important for the projecting climate change impacts on ecosystem processes.In recent decades,earlier spring phenology under climatic warming has well been documented.However,most studies on plant phenology under climatic warming are based on increased global average temperature,without taking the temporal discrepancy of the temperature increase into account.The study was conducted in a temperate steppe in Duolun Restoration Ecology Research Station in Inner Mongolia of Northern China.The experiment included four treatments: Control(C),Day warming(D),Night warming(N),and Whole-day warming(W).The normalized difference vegetation index(NDVI)and two-year phenological observations were used to examine temperate steppe in response to climate change under a long-term asymmetric day and night warming.Across the two years,the results showed that:(1)At species level,plant phenology showed significant interannual variability and different response patterns to day and night warming.Plant phenology in 2014 showed greater sensitivity to experimental warming than that in 2013.In addition,plant phenology is more sensitive to night than day warming.Day warming did not affect plant flowering and fruiting time whereas night warming advanced the flowering and fruiting time,but did not impact the reproductive duration of some species.Growth period of plants was not changed under experimental warming.Night warming led to decreased overlapp of species phenophase,suggesting that climatic warming may reduce resources competitions and increase complementary of resources among species.(2)At community level,day warming significantly delayed the end of growing season,resulting in the extension of the growing season.Night warming had no impacts on the start and end of the growing season.(3)Functional traits of plants have close relationships.Phenological sensitivity showed a negative relationship with coverage sensitivity of dominance plant species.The result indicates that the coverage of plant species that have advanced phenophase may increase.However,the coverage of other plant species that have not changed phenophase may decrease,leading to increased risk of extinction.Our findings can help to better understand and predict the responses of plant phenology to climate warming and facilitate the determination the priority of the protection of plant species.