Influence of simulated warming on light and CO_2 utilization capacities of lakeside dominant plants in a typical plateau wetland in northwestern Yunnan
The influence of air warming on the photosynthesis of wetland plants and the underlying mechanisms has recently been one of the important topics in ecological research. Using the open-top chambers (OTC),we studied the influence of experimental air warming on the light and CO_2utilization capacities and photosynthetic rate of two dominant species ( Zizania caduciflora and Sparganium stoloniferum) on the lakeside of Napahai plateau wetland in northwestern Yunnan. The results showed that ( 1) the effects of warming on light and CO_2 utilization capacities were species-specific. For Z. caduciflora,air warming significantly decreased the light saturation point, light compensation point, light utilization range, CO_2 saturation point, CO_2 utilization range, and maximum net photosynthetic rate, but it increased the CO_2 compensation point. In contrast, in S. stoloniferum,air warming significantly increased the light saturation point, light utilization range, and maximum net photosynthetic rate, but it decreased the light compensation point and weakly influenced the CO_2 utilization parameters. (2) The effect of air warming on the light and CO_2 utilization capacities of the two plant species showed seasonal variation. In Z. caduciflora,under the three temperature treatments, the light saturation point and light utilization range in October were significantly lower than those in June and August, and a seasonal decrease was observed in its maximum net photosynthetic rate. Contrarily, in S. stoloniferum,both the light and CO_2 utilization parameters were not influenced by air warming,but its maximum net photosynthetic rate was higher in August than that in June and October. (3) All temperature parameters were negatively correlated with photosynthetic parameters in Z. caduciflora,whereas they were positively correlated in S. stoloniferum. The diurnal temperature was the major factor influencing the maximum net photosynthetic rate and light utilization range,while the mean and minimum temperatures mainly affected the CO_2 utilization range. This study indicates that the lakeside dominant plants in northwestern Yunnan plateau show different adaptive strategies to air warming. In the context of continuous climate warming in northwestern Yunnan,the dominate status of Z. caduciflora might get weakened, while that of S. stoloniferum might get strengthened, and these changes, in turn, can induce alterations in vegetative components,structures,and functions of the whole ecosystem.