入侵植物加拿大一枝黄花对土壤水分变化的生态学响应

以盆栽的入侵植物加拿大一枝黄花为材料,在100%(CK)、80%(W_80)、60%(W_60)和40%(W_40)土壤田间持水量条件下,研究了该植物的生长、生物量分配和光合生理特征,以探讨其入侵机制.结果表明:(1)加拿大一枝黄花的生长速率、株高、叶面积(叶长、叶宽)等均随土壤含水量的降低而下降;总生物量及根、茎、叶各器官生物量积累均随土壤含水量的减少而呈不同程度降低,根生物量比、叶生物量比和根冠比则表现出逐渐增大趋势,并在W_40处理下达到最大;克隆生长在W_40处理下受到严重抑制,表现为无克隆分株和二级根茎,分枝强度低、根茎直径小等特征.(2)随着土壤含水量减少,植株叶绿素a、叶绿素b和叶绿素总量逐渐下降,叶绿素a/b比值却升高,同期的净光合速率、最大净光合速率、光饱和点下降,而光补偿点却上升,其光适应范围逐渐变小.研究发现,加拿大一枝黄花具有较强的抗旱性和耐旱性,但重度干旱仍严重影响其正常生长,其适宜的水分生态位是中偏湿的土壤环境;其通过一系列形态和生理上的可塑性变化来适应和占据各种异质性生境,表型可塑性可能是其成功入侵的重要机制.

Ecological Responses of the Invasive Alien Plant Solidago canadensis to Changes of Soil Water Content

A pot experiment was conducted to study the growth,biomass allocation and photosynthetic characteristics of the invasive alien plant Solidago canadensis in four different soil water contents which corresponded to relative soil water content 100%(CK),80%(W_80),60%(W_60) and 40%(W_40),and explore the mechanism of its invasion.The results were as follows:growth rate,height,leaf area (leaf width and length) decreased significantly with the decrease of soil water content.As soil water content decreased,the total biomass,root biomass,stem biomass and leaf biomass reduced in varying degrees,while root mass ratio,leaf mass ratio and root cap ratio showed the gradually increasing trend,reaching the climax at W_40.Clonal growth of S.canadensis was inhibited severely at W_40,showing no ramets and secondary rhizomes,small rhizome diameter and low branching intensity.The contents of chlorophyll a,chlorophyll b and chlorophyll (a+b) of S.canadensis increased with the decrease of soil water content,while the ratio of chlorophyll a/b increased;Compared to CK(100%),the net photosynthetic rate,the maximum photosynthetic rate and light saturation point are lower and light compensation point is higher at the same period,so the range of light adaption is narrower under the other three treatments.In summary,the results suggested that S.canadensis has strong ability of drought resistance and endurance,but severe drought could affect the normal growth of them;The suitable water niche for S.canadensis is fairly wet soil environment and they adapted themselves to all kinds of heterogeous habitats through changes in morphological and physiological characteristics.So it is concluded that phenotypic plasticity could be an important invasive mechanism of S.canadensis.