The Spatio-temporal Variation Of The Floral Traits Of Rhododendron Przewalskii In The Headwater Region Of Minjiang River And Its Pollination Ecology

As a unique geographic unit,the Qinghai-Tibet Plateau is one of the most complex regions in the world and one of the most sensitive regions to global changes.The reproductive characteristics of plants are an important feature of species survival,settlement and population expansion,and this feature is greatly affected by the environment under the background of global climate change.Exploring the differences in reproduction strategies and resource allocation in heterogeneous environments will help to understand and predict the future dynamics of plant populations.This article uses Rhododendron przewalskii Maxim as the research object to compare and analyze the spatiao-temporal variation of its floral traitsand biomass distribution,preliminary analysis of the pollination efficiency of R.przewalskii and the differences of pollinator types between altitudes,provide a scientific basis for the response mode of plant reproduction ecology to environmental changes and the protection of biodiversity in the Qinghai-Tibet Plateau.In this study,three sample plots in Gonggangling,Doujitai,and Kakas Mountains were selected in Songpan County,the headwater region of Minjiang river.They were sampled in the field during the flowering period(May-June)of R.przewalskiiin 2019 and 2020.The distribution altitude setting sample is taken from the twig in the flowering period,and the spatiao-temporalvariation of floralr traits(altitude,aspect,interannual)and the trade-off relationship between the components are compared and analyzed.In 2020,a field pollination control experiment was carried out in Kaka Mountains to compare and analyze the pollination efficiency of R.przewalskii and at different altitudes and the differences in pollinator types.The main results are as follows.(1)The low-altitude corolla of Gonggangling site is small and the corolla tube is slender,while the high-altitude has a large corolla but the corolla tube is stubby.there is no significant difference in the shape of the corolla between the elevations of the Doujitai site,and the middle-elevation corolla is the smallest.Kaka Mountains There is no significant difference in corolla size between the altitudes of the plots,but the corolla tube at high altitudes is more open than other altitudes.The length of style,ovary,pistil and pedicel at high altitude is longer than low altitude in Gonggangling,while Doujitai and Kaka Mountains show that styles,ovary,pistil and pedicel become shorter with increasing altitude.Thefloraltraits in different aspect directions on the Kaka Mountains are as follows.the corolla on the east aspect is significantly larger than the northeast aspect.Combined with the analysis of the soil environment,soil temperature,soil bulk density and p H may be the reasons for the differences in floral traits.There is no significant difference in the size of the corolla in the Kaka Mountains.The corolla groove becomes shallower(that is,the pistil is more exposed),and the length of style,ovary,pistil and pedicel becomes shorter as the year grows.(2)Floral opening diameter-Corolla tube length is significantly correlated at high altitudes,and is a constant growth relationship.The pistil length-Corolla tube length is significantly correlated at low altitudes.It is an allometric relationship and the growth rate of the pistil is greater than the growth rate of the corolla tube length.The length of the pistil plays a major role in the adjustment of the distance from the stigma.The biomass distribution of leaves in twigs is relatively high,and the average biomass between altitudes accounts for about 53.25%.Corolla has a higher biomass distribution among floral components,and the average biomass between altitudes accounts for57.75%.(3)Pollinators of R.przewalskiiinclude birds,medium-sized Hymenoptera(ants)and Diptera insects,small Diptera insects and very small insects.Smaller Diptera insects at low altitude are the main effective pollinators.However,high-altitude birds are the main effective pollinators.To sum up,in the heterogeneous habitat,R.przewalskii has greater variability in the floral traits within the species,so that R.przewalskii has a higher chance of reproduction in the alpine habitat,which is conducive to the stability and expansion of its population.In addition to soil conditions,climatic factors and the choice of pollinators also play a role in regulating the traits of flowral.In apine areas,wind-borne insect-borne plants with mixed pollination systems of wind-borne and insect-borne insects have more advantages in reproduction.