| Global climate has been significantly changed with the development of human industrialization process.Rising atmosphere carbon dioxide concentration caused by the combustion of fossil fuel resulted in climate warming and changes in precipitation regimes.Models have predicted that the frequency of extreme precipitation events(e.g.,drought and flood)would increase in the future.Plant phonology,which has been used as an indicative index for climate change,is sensitive to climate change.However,most of the previous studies focused on the impacts of drought and/or increased precipitation on phenology,but how plant phenology responds to a gradient of precipitation change remains elusive.Moreover,semi-arid grassland is limited by precipitation.A manipulation experiment including increased(20%,40%,60%),ambient,and decreased precipitation(20%,40%,60%)treatments was conducted to examine the response of plant phenology to changing precipitation amount in the semi-arid grassland in Inner Mongolia.Precipitation treatments were terminated in 2013 to study the recovery capacity of plant production.In this study,phenology of three dominant species was examined in the late growing season of 2012,and phenology of 10 dominant species was observed in 2013-2014.Across the three-year,the results showed that:(1)in the treatment year(2012),the phenology of plant species had different responses along the precipitation gradient.The flowering time of Stipa krylovii was delayed for 7.8 days in the-60% precipitation plots,but showed no response to the increased precipitation treatment.There was no response of Artemisia frigida phenology to the precipitation treatments.The developed root system and high absorptive capacity of Artemisia frigida may explain the insensitive response of its phenology to changes in soil water availability.Advanced flowering time of Cleistogenes squarrosa was found under both increased and decreased precipitation,largely due to small plant size of Cleistogenes squarrosa,which makes the light requirements greater than the water demand.(2)Drought delayed flowering of Stipa krylovii in 2012,but advanced flowering time for 11.2 days(P < 0.001)than the control in 2013.It could have been explained by the reduction in the plant community cover and species richness under the decreased precipitation treatments in 2012.Stipa krylovii under the drought treatment subjected to lower competitive pressures than the control treatment in 2013.In the recovery period of drought,the species competition shifts from water resource belowground into light resource aboveground.Plants with higher stature like Stipa krylovii may have great competitive advantage for light and rapid growth.(3)Plant community subjected to the previous drought treatments showed early flowering during the recovery phase.In the period of drought recovery(2013-2014),the flowering time of grasses and forbs were significantly advanced by 2.3(P < 0.05)and 0.9 days(P < 0.1),respectively.Early-and late-flowering species were advanced by 1.9(P < 0.05)and 2.2 days(P < 0.05),respectively.The results showed that flowering phenology was earlier at the community level,resulting from the evolutionary adaptation of plant offspring in the semi-arid grassland which could advance flowering time to avoid drought.Our results indicate that the differential phenology responses of plant to changing precipitation regimes may be ascribed to the differences in plant height and water availability for roots.In the recovery period,community phenology was substantially advanced due to the rapid evolution of plants to adapt to the arid environments.The observations suggest that plant could recover productive capability after drought stress in the semi-arid ecosystem.In addition,our findings can facilitate the projection of plant phenology in response to precipitation changes and grassland ecosystem management under future climate change scenario. |
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