氮沉降对蒙古栎幼苗生长及光合特性的影响

Effects of simulated nitrogen deposition on growth and photosynthetic characteristics of Quercus mongolica seedlings

以吉林省舒兰市人工造林的蒙古栎幼苗为研究对象,设置空白对照(CK,0 kg·hm^(-2)·a^(-1)),低氮(LN,50 kg·hm^(-2)·a^(-1))和高氮(HN,100 kg·hm^(-2)·a^(-1))3种氮浓度处理,模拟自然氮沉降,揭示蒙古栎幼苗光合生理生态特性随氮浓度的变化规律。结果表明,蒙古栎幼苗的净光合速率(P_(n))随着氮浓度的升高呈现出先升高后降低的变化趋势。在LN处理下,蒙古栎幼苗的苗高和地径与CK相比分别增加了8.68%和23.34%,叶绿素相对含量较CK升高了13.17%。在HN处理下,蒙古栎幼苗叶片的气孔导度(G_(s))较LN处理下降了37.81%,最大羧化速率与最大电子传递速率较CK及LN处理均显著下降(P<0.05)。说明LN处理提升了叶片的叶绿素相对含量和P_(n),从而促进了幼苗的生长,提高了幼苗的光合生产力(G);而HN处理则引起G_(s)的下降,削弱光系统电子传递能力,减弱叶片的P_(n),使幼苗的G受到抑制,不利于幼苗生长。

This study aims to investigate the effects of simulated nitrogen(N)deposition on the photosynthesis of Quercus mongolica in Shulan,Jilin Province.The N addition gradient was designed to three levels:blank control(CK,0 kg·hm^(-2)·a^(-1)),low N addition(LN,50 kg·hm^(-2)·a^(-1)),and high N addition(HN,100 kg·hm^(-2)·a^(-1)).The results revealed different response mechanisms of Q.mongolica seedlings to three N addition levels.It was found that the net photosynthetic rate(P_(n))of Q.mongolica seedlings increased under LN treatment and decreased under HN treatment.Compared with the CK treatment,the height and ground diameter of Q.mongolica seedlings under LN treatment increased by 8.68%and 23.34%respectively,and the chlorophyll content increased by 13.17%.Under the HN treatment,the stomatal conductance(G_(s))decreased by 37.81%compared with the LN treatment,and the maximum rate of carboxylation and maximum rate of electron transport of Q.mongolica seedlings decreased significantly compared with the CK and LN treatment(P<0.05).In general,the LN treatment promoted seedling growth and improved the photosynthetic productivity(G)of seedlings by increasing chlorophyll content and P_(n)of leaves.The HN treatment decreased the G_(s)and the electron transfer ability of the photosystem,weakened the P_(n)of leaves,and inhibited the G of seedlings,which was not conducive to seedling growth.