喜旱莲子草和接骨草竞争对模拟增温的响应

Responses of the competition between Alternanthera philoxeroides and Sambucus chinensis to simulated warming

研究外来入侵植物与本地植物种竞争对气候变暖的响应,对于预测未来气候变化背景下入侵植物的入侵趋势、理解其入侵机制以及筛选生态替代种具有重要的意义。以入侵我国的外来植物喜旱莲子草(Alternanthera philoxeroides)和本地植物种接骨草(Sambucus chinensis)为材料,通过两种植物单栽、纯栽和混栽,采用红外辐射加热器模拟增温,研究了两种植物竞争对模拟增温的响应。结果表明:(1)在模拟增温期间(2013年5–12月),增温组空气平均温度比不增温组提高了0.47℃,相对湿度降低了1.87%;(2)混栽的喜旱莲子草除根冠比与单栽无显著差异外,其余各生物量和根系形态指标均显著低于单栽喜旱莲子草;无竞争、种间竞争和种内竞争三种竞争间,接骨草除根冠比、细根与总根生物量比、比根长和比根表面积无显著差异外,其余指标均呈现无竞争>种间竞争>种内竞争的趋势;(3)无竞争、种间竞争和种内竞争三种条件下,喜旱莲子草各指标在增温和不增温处理间差异均不显著,而接骨草总生物量和根生物量在无竞争和种间竞争条件下增温处理均显著低于不增温处理,在种内竞争条件下则相反;(4)增温使接骨草的相对拥挤系数降低,接骨草对温度升高反应敏感,而喜旱莲子草则表现出一定的适应性。由此推测,在中度遮阴陆生生境中,接骨草有望成为喜旱莲子草生物替代控制的材料。

Aims Research on how competition between invasive and native plants responds to simulated warming can provide insights into the trends and mechanisms of plant invasion,and profoundly helps to screen ecological substitutes under future climates. Our objective was to explore the effects of simulated warming on competition between an invasive species Alternanthera philoxeroides and a native plant Sambucus chinensis. Methods An experiment was conducted from May to December 2013 with the same five competition scenarios being arranged for under both warming and non-warming environments. Simulated warming was created by using infrared heater. Competition scenarios included non-competition（one plant per pot）,intraspecific competition（two plants of the same species per pot） and interspecific competition（one plant for each species per pot）. Biomass and root morphological variables were investigated of the plants under different warming and competition treatments.Important findings（1） The average air temperature of the simulated warming environment was 0.47 °C higher than that of the non-warming environment,but the relative air humidity was decreased by 1.87% by the simulated warming.（2） Compared with the non-competition scenario,the values of all variables in A. philoxeroides under interspecific competition were significantly lower except the root/shoot ratio,which had no significant difference between the non-competition and interspecific competition scenarios. Root/shoot ratio,the biomass ratio of fine root to total root,relative root length and relative root surface area in S. chinensis did not show significant differences among the three competition scenarios; whereas other variables in S. chinensis decreased significantly following a pattern of non-competition interspecific competition intraspecific competition.（3） The effect of warming was not significant under any of the three competition scenarios in A. philoxeroides,but it varied withcompetition scenarios in S. chinensis. The warming treatment significantly decreased the total biomass and root biomass in S. chinensis under non-competition and interspecific competition scenarios,but it increased the values of the two variables in S. chinensis under the intraspecific competition scenario.（4） The relative crowding coefficient for S. chinensis decreased with warming,reflecting the sensitivity of the species to warming; whereas A. philoxeroides had some adaptability to warming. Therefore,S. chinensis can be a potential ecological substitute for A. philoxeroides under moderate shade in terrestrial habitat.