模拟氮沉降对入侵植物薇甘菊叶绿素荧光参数的影响

大气氮沉降的增加会对某些生态系统造成严重影响。入侵植物薇甘菊的蔓延是近年来威胁我国林业安全的一大难题。氮沉降量的增加可能会对薇甘菊光合作用效率产生影响。为进一步了解两者之间的关系，以NH4NO3（分析纯）为氮源，对生长着薇甘菊（Mikania micrantha）的木荷（Schima superba）人工林试验地进行模拟氮沉降处理。试验设置3个氮沉降试验组，分别为对照组N0（N：0 g·m-2·a-1），试验组N5（N：5 g·m-2·a-1）和N10（N：10 g·m-2·a-1），根据当地降水情况计算并定量人工喷施。于2013年6、8和11月分别测定试验地内薇甘菊的各项叶绿素荧光参数指标。结果显示，（1）各月份间，除非光化学猝灭（qN）6月份数值低于11月份外，各指标基本表现为8月份最高，6月份次之，11月份值最低的规律。在低温，相对干旱的11月，薇甘菊生长末期，氮素的增加对薇甘菊光合效率提高的帮助尤为明显。（2）各试验组间，N0组各指标值均低于N5组与N10组，氮沉降量的增加能够促进薇甘菊光合作用效率的提高，会对薇甘菊的生长具有促进作用。（3）试验组N5组与N10组之间无一致规律性，推测过高的氮素可能会抑制薇甘菊的生长。此推论有待于进一步实验证明。（4）在试验地自然条件下，大气氮沉降量的升高会促进薇甘菊光合作用效率的提高。该文可为大气氮沉降增加的生态影响的研究和薇甘菊入侵生态学研究提供一定的理论依据。

Effects of simulated nitrogen deposition on the chlorophyll fluorescence parameters of the invasive plant Mikania micrantha

The increasing of atmospheric nitrogen deposition had seriously imperiled some ecosystems. The excessive growth of Mikania micrantha had become a severe stress to the forest. The authors tried to reveal the relationship between atmospheric nitrogen deposition and the growth of Mikania micrantha. Using NH4NO3 as the nitrogen source, a simulated nitrogen deposition treatment of Mikania micrantha growing in an experimental field of Schima superb plantation was conducted. 3 nitrogen levels were set （N0 treatment：N 0 g·m-2·a-1. N5 treatment：N 5 g·m-2·a-1. And N10 treatment：N 10 g·m-2·a-1） according to the precipitation in the past years. The chlorophyll fluorescence parameters were determined in June, August and November. The results showed that, （1） compared the chlorophyll fluorescence parameters between each month, besides quenching coefficient （qN）, the parameters in august was the highest;that of June was the second class;and that of November was the lowest. To qN, the parameters in august was the highest; that of November was the second class and that of June was the lowest. The increasing of nitrogen deposition had more obvious effect in November. （2） Compared the chlorophyll fluorescence parameters between each experimental group, all parameters of N0 group was lower than the other two groups. The simulated nitrogen deposition had promoting effect on the photosynthesis rate of Mikania micrantha. （3） No regular pattern was applied between N5 group and N10 group. An inference was that excessive nitrogen might lead to growth inhibition. Yet it remained to be proved. （4） In summary, in the condition of local environment, the nitrogen deposition had promoting effect on the photosynthesis of Mikania micrantha.