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氮添加对高寒草甸植物功能群数量特征和光合作用的影响

沈豪,董世魁*,李帅,许驭丹,韩雨晖,张静   

  1. (北京师范大学环境学院, 水环境模拟国家重点实验室, 北京 100875)
  • 出版日期:2019-05-10 发布日期:2019-05-10

Effects of nitrogen addition on the quantitative characteristics and photosynthesis of different plant functional groups in an alpine meadow of Qinghai-Tibetan Plateau.

SHEN Hao, DONG Shi-kui*, LI Shuai, XU Yu-dan, HAN Yu-hui, ZHANG Jing   

  1. (State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China).
  • Online:2019-05-10 Published:2019-05-10

摘要:

氮沉降对植物群落的影响,特别是对脆弱生态系统中植物群落的影响,一直是生态学研究的热点问题。为了更好地探究氮沉降对脆弱生态系统植物群落不同功能群生理生态特征的影响,以青藏高原高寒草甸为研究对象,将植物群落划分为禾本科、莎草科、杂类草3种不同功能群,通过模拟氮沉降试验,观测不同氮添加水平下(0、8、24、40、56、72 kg·hm-2·a-1)3种功能群数量特征和净光合速率的动态变化,以期揭示植物对氮沉降的响应规律。结果显示:1)氮添加对不同功能群植物数量特征的影响具有显著差异,氮添加提高了莎草科的多度和高度,而对禾本科和杂类草的多度和高度无显著影响(P>0.05),禾本科的地上生物量随着氮添加水平的升高表现出先下降后上升的变化趋势,而莎草科和杂类草的地上生物量随着氮添加水平的升高均表现出下降趋势;2)氮添加对不同功能群植物光合作用的影响有显著差异,禾本科的净光合速率(Pn)随着氮添加水平的升高表现出先下降后上升的变化趋势,而莎草科和杂类草净光合速率均表现出线性下降趋势,氮添加显著提高了不同功能群植物的气孔导度(Gs)和蒸腾速率(Tr)。3)三个功能群植物的净光合速率与地上生物量之间均呈显著正相关。研究表明,短期高氮添加会削弱植物的光合能力,降低植物地上生物量的积累,抑制植物生长。
 

关键词: 镁含量, 微生物群落组成, 细根分解, 氮含量

Abstract: The effects of nitrogen deposition on plant communities, especially on the alpine meadow with relatively fragile habitats, have been hot topic in ecology. To better understand the effects of nitrogen deposition on the eco-physiology of different plant functional groups in the alpine meadow of Qinghai-Tibetan Plateau, we conducted a field experiment under different nitrogen addition levels (0, 8, 24, 40, 56, 72 kg·hm-2·a-1) to simulate natural nitrogen deposition. We classified the plant species into three functional groups, including grass, sedge, and forb. Results showed that: (1) The effects of nitrogen deposition on three functional groups were different. Nitrogen addition increased the abundance and height of sedge, but had no effects on that of grass and forb (P>0.05). Aboveground biomass of grass showed non-linear response to nitrogen addition, while the aboveground biomass of sedge and forb significantly decreased with the increases of nitrogen addition level. (2) Net photosynthetic rate of grass showed nonlinear response to nitrogen addition, while that of sedge and forb significantly decreased with the increases of nitrogen addition level. Nitrogen addition significantly increased the stomatal conductance (Gs) and transpiration rate (Tr) of all the three functional groups. (3) The net photosynthetic rate was significantly positively correlated with aboveground biomass of the three functional groups (P<0.05). In conclusion, short-term high nitrogen deposition will decrease the accumulation of plant aboveground biomass through reducing the photosynthetic capacity, and thus inhibiting plant growth in alpine meadow of Qinghai-Tibetan Plateau.

Key words: nitrogen concentration, fine root decomposition, microbial community composition, magnesium concentration