| Global climate change has become indubitable. According to IPCC (2007) Fourth Assessment Report, it predicts that global average temperatures will increase by 1.4-4.0℃from now to 2100. Wetland formed by the interaction between land and water, has a unique physical, chemical and biological structure and function. The response of wetland to climate warming must be distinct from other systems, so the effects of elevated temperature on wetland plants must be different from plants in other environments. A total number of 8 open top chamber (OTC) experiments were carried out in East Beach of Chongming Island of Shanghai in March 2008. The effects of elevated temperature (ET) on the growth, reproduction and physiological characteristics of reclamation Phragmites australis were examined from March to November in 2008. Our study has great reference value to predict the growth of wetland plants, changes in community structure and vegetation productivity under the condition of future global change. Results are as follows.1) In comparison with the control, the number of reeds sprout, shoot high, shoot biomass on March 5 and March 20 were significantly increased under the ET, which indicated that ET contributed to the growth of buds. On the study of the dynamic changes of plant height, we found that the plant height increased significantly. On the study of the dynamic changes of basal diameter, we found that basal diameter did not change significantly. Under the ET the plant height increased, but basal diameter did not change, which made Phragmites australis susceptible to lodging, and would have negative effect. RGR increased significantly in response to the ET, which shows the growth rate accelerated on ET. The research of Rb showed that the response degree of growth to ET decreased gradually, with the maximum in germination stage.2) The effect of ET on leaf numbers and leaf spacing was not significant, and treatment ET made the height of bottom leave increase significantly, from which we can conclude that plant height increased with leaf numbers and leaf spacing unchanged and an overall increase in the height of all the leaves. Under the ET, leaf length and leaf width increased significantly by 8.7%,8.6%, respectively, compared with the control. The area of bottom leave did not change remarkably, but the area of top leave increased significantly by 43.6%. The study of the dynamic changes of leave areas from April to September showed that the leave areas increased significantly. Further study found that the effect of ET on LMR, SLA and LAR was different. ET had no significant effect on leaf mass ratio (LMR), but specific leaf area (SLA) and leaf area ratio (LAR) decreased significantly with increasing temperature.3) Aboveground biomass was significantly increased and the biomass of 0-60cm,60-120cm,120-180cm,>180cm increased significantly by 27.9%,36.6%, 38.2%,41.4% compared with the control. Under the ET every layer of underground biomass changed differently. The upper (0-20cm) increased significantly by 35.9%, the middle (20-40cm) decreased significantly by 23.0%, but the lower (40-60cm) did not change remarkably. The effects of ET on the biomass of different organ were different. The biomass of root, stem and leave increased significantly, and the biomass of flower decreased significantly under the ET. The study also found that when temperature increased, the root and flower biomass ratio of the total biomass decreased significantly, stem and leaf biomass percentage increased significantly.4) Under the ET the number of individuals flowering and flowering rates were significantly reduced by 37.5%,83.4%, respectively. ET changed the shape of inflorescence. When the temperature increased, inflorescence high, flower neck length, round distance, sprig number, twig length, number of ears, ear length, flower number/ round, flower number/twig, and flower number/plant were significantly reduced, in addition to round numbers of inflorescence. Moreover, the number of seeds and the total number of seeds decreased significantly by 25.0%,48.9%, with temperature increasing. This shows that the ET inhibited not only flowering and number of seeds, but also on the shape and size of the inflorescence.5) The effects of ET on different physiological features were different. In Pn-PAR curves, under the ET net photosynthetic rate (Pn), light compensation point and light saturation point improved significantly. The effects of ET on stomatal conductance were related to PAR. When PAR<900μmol.m-2.s-1, the stomatal conductance increased; but when PAR> 900μmol.m-2.s-1, the stomatal conductance decreased. We also found that transpiration increased significantly, water use efficiency was reduced significantly, and soil respiration rate improved significantly.
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