白花鬼针草在入侵过程中的叶功能性状变化特点及其与环境因子的关系

Changes of leaf functional traits and their relationship with environmental factors during the invasion of Bidens alba

叶片是植物获取资源的重要器官,探究叶功能性状之间相关性的变化规律以及对环境因子的响应,有利于理解生物的入侵机制。以城市植物群落中3种入侵程度(轻度入侵、中度入侵、重度入侵)的白花鬼针草(Bidens alba)为研究对象,测定了其14个叶功能性状与5个环境因子(光强、大气湿度、土壤理化性质)。运用单因素方差分析、相关性分析、冗余分析等方法分析其在入侵过程中资源分配格局、吸收利用策略。结果表明:(1)随着入侵程度加重,其叶片宽度、叶面积、叶干重、叶干物质含量、叶全磷含量显著升高;比叶面积、叶全氮含量在中度入侵下最高;叶厚度、叶体积、叶鲜重在中度入侵下最低。(2)叶性状之间联系密切。轻度入侵下,叶长与叶宽、叶面积之间,叶鲜重与叶干重存在显著相关性。中度入侵下,叶全氮含量与叶全磷含量存在显著相关性。重度入侵下,比叶面积与叶干重、叶干物质含量、叶组织密度存在显著相关性。(3)冗余分析表明光照、土壤湿度是影响白花鬼针草入侵的主要因素。在其逐渐入侵的过程中,光照增强、土壤湿度减少促使其叶干物质含量、叶厚度、叶组织密度、叶全碳含量增加,比叶面积降低。白花鬼针草的适应策略从入侵早期的资源获取型转变成入侵后期的资源保守型。综上,在外界条件压力逐渐增加的情况下,白花鬼针草在轻度入侵-中度入侵过程中倾向于采取获取型策略(低投入-高收益)。在中度入侵-重度入侵过程中,其策略会转向资源保守型策略(高投入-低收益)。

For plants,their leaf is an important organ to obtain resources.It is conducive to understanding the biological invasion mechanism by exploring the relationship among leaf functional traits and responses to environmental factors.In this study,we focused on Bidens alba,a species with three levels of invasion(mild,moderate,and severe)in urban plant communities and measured its 14 leaf functional traits and 5 environmental factors(light intensity,atmospheric humidity,and soil physical and chemical properties).Additionally,we analyzed the resource allocation pattern,absorption and utilization strategy in the process of invasion by one-way ANOVA,correlation analysis,redundancy analysis and other methods.The results showed that:(1)As the degree of invasion increased,several leaf traits also changed significantly.Specifically,leaf width,leaf area,leaf dry weight,leaf dry matter content and leaf total phosphorus content increased significantly with the increase of invasion degree.There were the highest specific leaf area and leaf total nitrogen content under moderate invasion.There were the lowest leaf thickness,leaf volume and fresh weight under moderate invasion.(2)There was close relationship among leaf functional traits.In mild invasion degree,the leaf length was observably correlated with leaf width and leaf area.Leaf fresh weight was observably correlated with leaf dry weight.There was significant correlation between leaf total nitrogen content and leaf total phosphorus content under moderate invasion.The specific leaf area was significantly correlated with leaf dry weight,leaf dry matter content,and leaf tissue density under severe invasion.(3)Redundancy analysis showed that light intensity and soil humidity were the main factors affecting the invasion of Bidens alba.In the process of invasion,the increase of light intensity and the decrease of soil humidity caused the increase of leaf dry matter content,leaf thickness,leaf tissue density and leaf total carbon,and the decrease of leaf area.These changes suggested a shift in the adaptation strategy of Bidens alba from resource acquisition in the early stages of invasion to resource conservation in the later stages.To sum up,under the increasing pressure of external conditions,Bidens alba tended to adopt different strategies at various stages of invasion.In the process of mild invasions to moderate invasions,Bidens alba tended to adopt acquisition strategy(low input-high return).But as the invasion progressed from moderate to severe,its strategy shifted to resource conservation(high input-low return).