Response Characteristics Of Flowering Phenology Of Different Plants To Climate Change And Grazing Utilization In Alpine Grasslands

Plant phenology is regular characteristics of physiological and growth response of plants according to seasonal environmental changes.Their changes are not only extremely sensitive to the characteristics of living environmental conditions but also indicate the characteristics of changes in plant communities,and even as well as ecosystem.In the context of global climate change,the temperature changes in the Qinghai-Tibet Plateau are nearly twice higher than the average global climate changes.Extreme weather phenomena,such as spring-snow disasters are becoming more frequent,and the land-use patterns like livestock grazing are also unprecedented changes.However,researches on independent and interactive effects of the changing characteristics of these environmental conditions on the phenology of alpine plants is very scarce limited,which restricts people to predict future changes in characteristics of alpine and grassland ecosystem,also effects to effective strategies and correct countermeasures for ecosystem protection and grassland management.Based on the dominance of typical alpine meadow and the five common plant species in the Namco region,Tibet,the Kobresia pygmaea,Potentilla fruticose,Leontopodium pusillum,Potentilla saundersiana,and Astragalus rigidulus were selected as the research objects to simulate climate warming by using the OTC_S(Open Top Chambers)of the International Tundra Program standard,while using artificially snow addition to simulate extreme snow disaster in early spring.Regular(once in June,July,and mid-August),fixed-site(grazing treatment area),and quantitative(1 yak for 3 consecutive days each time)were used to simulate moderate grazing conditions,to explore the characteristics,processes,and mechanisms of independent and interactive studies on the effects of warming,early spring snowstorm and moderate grazing on the date of first flowering,date of the last flowering and the flowering duration of each plant and we found:(1)That first flowering date of Kobresia pygmaea started in mid-May on average,but the first flowering date was significantly delayed under the snow addition.Other treatments have no significant effect on the first flowering date of Kobresia pygmaea;the last flowering date of Kobresia pygmaea starts at the end of May,but it was advanced under the annual warming treatment,and it was delayed by snow addition in early spring under the growing season warming;the flowering duration of Kobresia pygmaea was significant difference than the control under the treatments of snow addition alone,snow and grazing,annual warming and snow growing season warming.(2)The first flowering date of Potentilla fruticose was begun at the beginning of July on average,and there was no significant difference under the different treatments on the first flowering date of Potentilla fruticose;the average the last flowering date of Potentilla fruticose was started at the end of July,but it was significantly different from that of the control under grazing and snowing growing season warming.The last flowering date was delayed under the condition of annual warming,but advanced under the condition of growing season warming;There were significant differences in the flowering duration under the conditions of snow,snow grazing,annual warming,and snow growing season warming.(3)The average the first flowering date of Leontopodium pusillum was begun at the end of June,but the first flowering date was significantly delayed under the conditions of annual warming;the average of the last flowering date was begun in the middle of July,but it was significantly delayed under the snow conditions,and significantly shortened the flowering duration under the conditions of annual warming(4)The first flowering date of Potentilla saundersiana was begun in early June,the first flowering date was advanced under the annual warming condition,but the first flowering date was delayed under the snow condition;the last flowering date was started at the end of July on average,and last flowering date and the flowering duration is significantly between different years.(5)The first flowering date and the flowering duration of Astragalus rigidulus was significantly between different years and the first flowering date was started in early July on average,while the last flowering date was started in mid-August,and which was significantly delayed under snow addition.Although warming,early spring,and snow addition were affected the first flowering date,last flowering date,and flowering duration of the five species to different degrees,the response characteristics of different species were inconsistent.The flowering phenology of early-flowering and shallow-rooted plants(eg,Kobresia pygmaea)was more sensitive to the availability of soil moisture in early spring,but the flowering phenology of mid-flowering and late-flowering plants are more sensitive to temperature conditions.However,grazing did not affect the flowering phenology of all the five object alpine plant species either independently or in combination with warming and snow treatments.