Synergistic Effect Of Season, Simulated Warming And Nitrogen Deposition On Reproductive Characteristics And Allometry Of Ephemerals Cardamine Hirsuta

The issue of global warming and nitrogen deposition of global change must not be ignored which directly affect the ecological environment. Temperature and nitrogen are important factors in the process of plant growth, meanwhile, density is also the important natural selection pressure; the influence of different season of environment change on plant is also different, the plant deal with environmental changes accordingly through moderating the development of itself. this study analyzed the influences of simulating warming in spring and autumn and nitrogen deposition in growth characteristics, biomass accumulation and allocation, flowering phenology, fruit traits and allometry of ephemerals Cardamine hirsute with different population density, in an attempt to explore the adaptive characteristics respond to environment heterogeneity under the background of global climatic warming, in order to provide scientific evidence and support for rational use and protection of ephemerals resources, and provide theoretical evidence for the solutions of climate warming. The main results are as follows:(1) Warming promoted the growth of height both in spring and autumn, and had significant influences in autumn, meanwhile, the height of Cardamine hirsute in autumn significantly higher than spring after sowing 25 days. Crown area growing period in autumn was longer than spring, and low density was significantly longer than high density. The individual biomass of Cardamine hirsute in spring was far greater than autumn, warming significantly increased the biomass of low density and moderate density, while there was no significant difference in high density. Warming increased leaf biomass allocation, reduced reproduction allocation, root crown ration and root mass ration increased with density, in the whole, stem mass ration and leaf mass ration were lower in high density than low density in CK, fruits number was higher in spring, and was significantly increased in low density, thousand seed weight significantly decreased with density in CK and was smaller in autumn than spring. Root and above-ground biomass were both allometric relationship in spring and autumn, and the growth rate of root biomass was less than above-ground biomass, meanwhile, root-aboveground biomass allometric exponent in warming treatments was higher than CK, the allometric relationship of other modular biomass and above-ground biomass showed obvious differences in spring and autumn, spring was allometric relationship, while spring was isometric relationship except for leaf-aboveground biomass in CK. Overall, spring and warming were more beneficial to the growth and reproduction of Cardamine hirsute.(2) The height of Cardamine hirsute was higher in warming treatments and nitrogen deposition treatments than CK, that was OTCN>OTC>CKN>CK. In low density, warming and nitrogen deposition treatments were favorable for the growth of crown area, and the difference was not significant with the increase of density and the change of growing period. Nitrogen deposition increased the stem, leaf, reproductive organ and individual total biomass in a certain degree. The effects of warming and nitrogen deposition on modular biomass of Cardamine hirsute were different with different density, the influence of nitrogen deposition was bigger than warming in low density, and there was no significant difference in high density, nitrogen deposition reduced the root mass ratio. Warming reduced modular biomass-density allometric exponent, while nitrogen deposition increased, and the allometric exponent increased with extension of time. Warming and nitrogen deposition increased root-aboveground biomass allometric exponent, and the intercept of warming was larger than CK, the stem-aboveground biomass was allometric relationship in the early growing period with nitrogen deposition treatment and then transferred to isometric relationship, but there was no significant difference in leaf-aboveground biomass allometric relationship.(3) Flower duration in autumn was shorter than spring, but flowering onset advanced in autumn, and warming in spring significantly prolonged flower duration, while no significant difference in autumn, in the whole, spring and warming are advantageous to the reproduction of Cardamine hirsute, whether warming or not in autumn, there were no significant influence in flower duration, Cardamine hirsute end the phenology ahead of time in high density, and flower number was lower than low density. Warming and nitrogen deposition advanced flowering onset and lengthen flower duration, and flower duration was longer in low density compared with other treatments, the coefficient of them can promote flower phenology, at the same time, warming and nitrogen deposition increased flower number in low density to a certain degree, while in high density, there were no significant difference among each treatment.