土壤氮含量是影响植物生长发育的主要限制因素,氮素的增加会提高外来植物的入侵性.采用de Wit取代试验和增施氮肥的方法,在盆栽条件下,依据植株形态结构、生物量积累及分配等变化,研究了不同水平氮[0( CK) 、6、12、18、24 g /m~2]添加对入侵植物节节麦与小麦种间竞争关系的影响.结果表明:增施氮肥对节节麦与小麦的生长发育及种间竞争关系均造成了一定的影响.单种时,节节麦与小麦均表现了对氮营养的响应,随着施氮量的增加,根冠比、叶面积比呈下降变化,依据总生物量及总叶面积增幅大小可知节节麦氮响应能力大于小麦;混栽时,随着施氮量的增加,节节麦与小麦根冠比同样呈下降变化,当施氮量大于12 g /m~2时,节节麦根冠比与CK差异达到显著水平( P < 0.05),而小麦则不明显,由此说明竞争条件下节节麦对氮素的敏感程度大于小麦.此外,除茎生物量及叶面积比外,节节麦其余5个指标的表型可塑性指数均大于小麦,节节麦对氮肥的高响应能力可能与其高效率的氮肥利用率有关.依据根生物量、地上生物量和总生物量计算得出的相对竞争强度及竞争攻击力系数结果显示,增施氮肥明显提高了节节麦的竞争效应及其地下部分竞争资源的优势.基于本文研究结果,节节麦在氮响应能力、表型可塑性及竞争能力方面均大于小麦,这可能是导致其在麦田中得以快速扩张蔓延的重要原因,而当前大气氮沉降逐渐增加的现状必定会促进节节麦的入侵,增加本地群落的可入侵性.
英文摘要:
Soil nitrogen ( N) availability is the most limiting factor for plant growth,and increased nitrogen levels heighten exotic species' invasiveness. We assessed the effects of inter-specific competition and nitrogen fertilization on growth of an invasive plant Aegilops tauschii in pot experiment. And the competition relation was analysed based on the change of morphology, structure,biomass accumulation and allocation under different nitrogen treatment. The monocultures of Aegilops tauschii and wheat exhibited considerable nitrogen acclimation ability with the increase of nitrogen fertilization level,their root /crown ration and leaf area ratio decreased. The increment of biomass growth with nitrogen fertilization level was Aegilops tauschii > wheat. When the amount of nitrogen application was more than 12 g /m~2,the root /crown of Aegilops tauschii decreased significantly ( P < 0.05),it also shows that the nitrogen responsiveness of Aegilops tauschii is more sensitive than wheat. Most of parameters of phenotypic plasticity of Aegilops tauschii were higher than wheat,indicating that the former was more sensitive to nitrogen application and that this may be partly explained by its superior nitrogen utilization efficiency. In fact,nitrogen addition obviously enhanced the competitive effects of Aegilops tauschii on wheat,particularly interspecific root competition,which was supported by the fact that RCI and AG calculated based on above-aground,below-ground and total biomass were positive,respectively. Our study indicated that nitrogen deposition associated with global change may facilitate the invasion of Aegilops tauschii,and may enhance the vulnerability of native communities to invasion.