Shifts In Plant Reproductive Phenology Under Global Change Factors In A Tibetan Alpine Meadow

Since the Industry Revolution,greenhouse gas concentration has been increasing rapidly due to intensified anthropogenic activities.As a consequence,climate warming,changing precipitation and nitrogen deposition have also been observed at both regional and global scales.Nowadays,the responses of ecosystem to global change factors have become a priority in the field of ecological research.Phenology,the study of the timing of biological events,is considered as a sensitive indictor of climate change.As an important component of terrestrial ecosystems,plants have the earliest and most obvious response to global change.Plant reproductive phenology is an important feature of plant phenology,and its changes can affect gene flow,population persistence and species distribution,and may lead to changes in plant community stability and ecosystem functioning.Most researches focused on forests in North Temperate Zone or Temperate Zone,where climate change signals are amplified.Phenological research in alpine meadows is still scarce,while it has great potential to indicate the responses to different climatic factors.Alpine plants are highly susceptible to climate change due to short growing season and extreme environmental conditions.In recent years,climate change and human activities have been resulting in great changes of abiotic and biotic factors which can greatly alter plant community composition and ecosystem functioning in the alpine areas.Therefore,it is of great scientific value to study the response of plant reproductive phenology to the global change factors in alpine meadows.We conducted a multi-factors experimental on the Qinghai-Tibet Plateau to explore the responses of plant reproductive phenology to global change factors.By simulating warming,nitrogen addition and precipitation changes,a total of 11 treatments were set:warming(W),nitrogen addition(N),reduced precipitation(PR),increased precipitation(PI),warming and nitrogen addition(W+N),nitrogen addition and increased precipitation(N+PI),nitrogen addition and reduced precipitation(N+PR),warming and increased precipitation(W+PI),warming and reduced precipitation(W+PR),warming,nitrogen addition and reduced precipitation(W+N+PR),warming,nitrogen addition and increased precipitation(W+N+PI).The changes of different reproductive phenology of 11 common plants(three functional groups)in a alpine meadow on the Qinghai-Tibet Plateau were studied by recording plant phenology during a growing season.The major results are showen below:1.The effects of warming:the flowering date of Kobresia capillifolia was significantly advanced by 7.4 days,flowering duration was significantly extended by 5.6 days,and reproductive duration was significantly extended by 11.8 days.The fruiting date of Anemone obtusiloba was significantly advanced by 9.1 days.The flowering date of Thalictrum alpinum was significantly advanced by 10.7 days.The flowering date of Veronica eriogyne was significantly advanced by 9.1 days,and fruiting date was 8.4 days earlier.The flowering date of Poa poophagorum was significantly advanced by 6.5 days.2.The effects of nitrogen addition:the flowering date of A.obtusiloba was significantly delayed by 7.7 days.The fruiting duration of Potentilla fragarioides was significantly shortened by 3.6 days.3.The effects of warming and nitrogen addition:the flowering date of K.capillifolia was significantly advanced by 7.6 days,flowering duration was extended by 5.3 days,and reproductive duration was extended by 13.9 days.The flowering duration date of A.obtusiloba was significantly shortened by 9.5 days.4.The effects of warming and increased precipitation:the flowering date of K.capillifolia was significantly advanced by 8.7 days,and the flowering duration was significantly extended by 5.4 days.The fruiting duration of Chamaesium paradoxum was significantly advanced by 4.9 days.The flowering date of V eriogyne was significantly advanced by 6.1 days,and the fruiting date was significantly advanced by 5.5 days.5.The effects of warming and reduced precipitation:the flowering date of K.capillifolia was significantly advanced by 8.3 days,and the flowering duration was significantly extended by 4.9 days.The flowering date of V.eriogyne was significantly advanced by 8.1 days,and the fruiting date was significantly advanced by 7.3 days.6.The effects of warming,nitrogen addition and increased precipitation:the flowering date of the K.capillifolia was significantly advanced by 4.9 days,the flowering duration was significantly extended by 4.4 days,and the reproductive duration was significantly extended by 13.4 days.The flowering duration of the A.obtusiloba was significantly shortened by 8 days.The flowering date of V.eriogyne was significantly advanced by 6.3 days.7.The effects of warming,nitrogen addition and reduced precipitation:the flowering date of K.capillifolia was significantly increased by 5 days,the flowering duration was extended by 4.1 days,and reproductive duration was extended by 11.1 days.The flowering duration of A.obtusiloba was significantly shortened by 8.3 days.8.The responses of different plant functional groups were also inconsistent.Warming significantly advanced the flowering date of all plant functional groups,significantly affected fruiting date of gramineae and forbs,and significantly affected the flowering duration of gramineae and cyperaceae.and significantly affected the reproductive duration of all functional groups.Nitrogen addition significantly affected the flowering date of cyperaceae and forbs.The impact of altered precipitation on functional groups was not clear.Nitrogen addition and altered precipitation had significant interactions with the flowering date and fruit duration of cyperaceae;warming and nitrogen addition had significant interactions with the flowering date of the forbs;warming and altered precipitation had significant interactions with the fruiting duration of gramineae.The major results show that warming is the main factor affecting the changes of plant reproductive phenology in an alpine meadow of the Qinghai-Tibet Plateau.The response degree was different during different phenological periods,and the effects of warming may be weakened when other global change factors existed.