施氮对典型草原克氏针茅光合特性的影响

Effects of nitrogen addition on photosynthetic characteristics of Stipa krylovii in typical steppe in Inner Mongolia

受人类活动的影响,大气氮沉降和极端干旱事件日益加剧,研究氮素添加对草原植被的影响,有助于理解未来草原生态系统对氮沉降和全球变化的响应.在2014年夏季内蒙古草原干旱事件发生期,通过内蒙古草原氮素添加试验,探讨了不同施氮水平(未施氮0g·m^(-2)、低施氮量4g·m^(-2)、中施氮量8g·m^(-2)和高施氮量16g·m^(-2))对克氏针茅(Stipa krylovii)光合特性的影响.结果表明:研究样地中克氏针茅受到了干旱胁迫,施氮提高了克氏针茅的气孔调节能力和光能转化效率.一定范围的施氮量(4、8g·m^(-2))有利于提高克氏针茅光能转化效率(Fv/Fm)、光化学淬灭系数(qP)和PSII实际光化学效率(ΦPSII)等叶绿素a荧光动力学参数,但过高的施氮水平并不能提高克氏针茅的荧光特性,甚至会产生抑制作用.低中氮(4、8g·m^(-2))和高氮(16g·m^(-2))条件下植物对干旱的适应机制存在差异,低中氮处理提高了克氏针茅的羧化酶活性和光化学中心光能转化效率,高氮提高了克氏针茅的气孔调节能力.

Nitrogen deposition and extreme droughts have been accelerated by anthropogenic activities. Studying effect of nitrogen addition on grassland vegetation contributes to understanding response of grassland ecosystem to nitrogen deposition and global change. Nitrogen addition experiment was done during grassland drought period in the summer of 2014 in Inner Mongolia. Effect of nitrogen level （0, 4, 8, 16 g ·m^-2） on photosynthetic characteristics of Stipa krylovii was examined. It was found that proper nitrogen addition could improve photosynthetic responses of Stipa kryiovii. The nitrogen addition level for optimal response of fluorescence characteristics of Stipa krylovii was 4 or 8 g ·m^-2. Stipa krylovii might have different resistance mechanism to drought under low and high nitrogen levels. Low nitrogen condition increased carboxylase activity and photochemical center energy conversion efficiency. High nitrogen instead increased stomata regulation of Stipa krylovii.