氮素添加对黄土高原典型草原植物比叶面积及其重要值的影响

为了解氮素沉降对草地群落植物生长策略和群落组成的影响,通过长期(2009-2012年)氮素添加野外控制试验,研究了黄土高原天然草地禾本科植物长芒草(Stipa bungeana)、赖草(Leymus secalinus),豆科植物达乌里胡枝子(Lespedeza davurica)以及菊科植物阿尔泰狗哇花 (Heteropappus altaicus) 4种植物在不同施氮水平下叶片比叶面积(SLA)和物种重要值(IV)的变化特征,并探讨了氮素添加对各种植物叶片SLA和物种重要值影响的内在联系.结果显示:沿施氮水平,禾草科植物长芒草和赖草叶片SLA增加幅度较小、物种重要值整体上呈现逐渐增加的趋势,非禾草科植物阿尔泰狗娃花和达乌里胡枝子叶片SLA增加幅度较大,物种重要值整体上呈降低的趋势,施氮对禾草科植物更有利;各物种的重要值与叶片SLA之间无相关关系;物种重要值随着氮素添加量增加所产生的变异系数与该物种在群落中的重要值大小成显著负相关.表明在干旱贫瘠环境中,植物叶片SLA保守性强、可塑性低;氮素沉降对禾草科植物更有利.

Effect of Nitrogen Addition on the Specific Leaf Area and Important Value of Dominant Species in the Typical Steppe of the Loess Plateau,China

Our objective was to examine the effect of nitrogen(N) enrichment on the specific leaf area (SLA) and important value (IV) of several species in the typical steppe grasslands of the Loess Plateau. A long-term N addition experiment was conducted to investigate the effects of increasing N inputs on the SLA and IV of four dominant species (Stipa bungeana, Leymus secalinus, Heteropappus altaicus and Lespedeza davurica) in the Loess Plateau natural grassland. The results showed that N addition enhanced the SLAs of all species and IVs of Stipa bungeana and Leymus secalinus, but decreased the IVs of Heteropappus altaicus and Lespedeza davurica. IV was not correlated with SLA, however, there was a strong negative correlation between IV and the coefficient of variation. These results indicated that the SLAs of plants in arid ecosystems were conservative and low plasticity. N addition was more favorable to gramineous than to forbs.