Population Dynamics Of Early And Late Flowering Alpine Plant Species Under Seasonal Warming

Biodiversity conservation under climate change is one of the most important ecological research topics at present.Effectively predicting the fate of species under future climate change is a major challenge for biodiversity conservation.Recently,the impact of climate warming on long-term population maintenance has received wide attention.However,previous studies mainly focused on the impacts of increased annual temperature or increased temperature during the growing season,while there are few studies considering seasonal warming,which greatly limits our ability to predict the fate of species under future climate warming.Therefore,it is essential to carry out researches to examine the effects of seasonal warming on population dynamics,and then accurately quantify how climate warming will affect the fate of species,so as to provide scientific guidelines for biodiversity conservation.Here,the demographic responses to the increase of temperature by 2 ℃ during spring,summer,autumn,winter or the whole year were examined for the early flowering plant Anemone geum subsp.ovalifolia(Brühl)R.P.Chaudhary and the late flowering plant Gentiana lawrencei var.farreri(Balf.F.)T.N.Ho on an alpine grassland of the Tibetan Plateau.Annual censuses were conducted in 2021 and 2022.The individual survival,growth,reproduction under warming treatments and ambient conditions were recorded during each annual census.The relationship between vital rates(surivival,growth and reproduction)and plant size were examined using the Generalized Linear Mixed Model(GLMM),and Integral Projection Models(IPMs)were constructed to simulate the long-term population dynamics under ambient and warming treatments.The main findings include:1)The survival probability of A.geum and G.lawrencei was the highest under spring warming treatment,but it was the lowest under year-around warming treatment;warming treatments increased the annual individual plant growth of A.geum,but decreased the annual individual plant growth of G.lawrencei;warming treatments decreased the reproductive probability of both study species,with the lowest value under spring warming treatment and the highest value under autumn warming treatment;2)Seasonal warming reduced the population growth rate(λ)of A.geum;specifically,the earlier the warming season,the lower the λ value,and the lowest value was observed under year-around warming treatment;the λ values of A.geum are greater than 1 under the control and all warming treatments,indicating that all populations are growing;the λ value of G.lawrencei increased under spring warming,but decreased under other warming treatments;specifically,the later the warming season,the lower the λ value,and the lowest value was observed under year-around warming treatment;the λ values of G.lawrencei are greater than 1 or close to 1 under the control and seasonal warming,indicating that all populations are growing or remain stable;the λvaule of G.lawrencei is below 1 under year-around warming treatment,indicating that year-around warming will lead to population declining;3)The elasticity analyses showed that the population growth rates of the two studied species were most sensitive to changes in individual survival under the control and all warming treatments,indicating that the survival of individuals was crucial to the population maintenance of the two studied species under the future climate warming;the Life Table Response Experiment(LTRE)analyses of the IPMs showed that the changes in λ values of A.geum under the warming were mainly caused by the changes in the fecundity and growth;however,the changes in λ values of G.lawrencei under warming were jointly determined by the changes in fecundity,survival and growth.Overall,this study shows that seasonal warming affect life cycle processes(i.e.,survival,growth and reproduction)to varying degrees,change the long-term population dynamics,and consequently affect the final fates of the early-flowering plant A.geum and late-flowering plant G.lawrencei.Although the population growth of the lateflowering species,G.lawrencei,increased under spring warming,the rest of the poulations of the two studied species all showed decreaed growth under warming,and the decline was highest under year-round warming.These results demonstrate that studies on the effects of seasonal warming on population dynamics are highly important to precisely predict the fates of plant species under different future climate warming scenarios.The findings in the current study can aid to reveal the mechanism of earlyflowering and late-flowering plant species in response to climate warming and provide guidelines for designing suitable management strategies for biodiversity conservation under future climate change.