【作者】 汤俊兵；

【导师】 安树青；

【作者基本信息】 南京大学 ， 生态学， 2011， 硕士

【摘要】 芦苇(Phragmites australis)正在入侵北美以互花米草(Spartina alterniflora)为优势种的生态系统,而互花米草及其后代正在威胁欧洲和中国东海岸以芦苇为优势种的生态系统。从世界范围来看,它们二者具有区域性的相互入侵特征。因此,研究环境因素如何影响芦苇与互花米草相互入侵机制具有重要的生态学价值。为了探讨环境因素如何影响湿地多年生草本植物芦苇和互花米草的相互入侵机制,该文选取了两种影响芦苇与互花米草竞争的因素：去叶干扰和氮浓度,从模拟动物啃食和土壤营养两种角度研究其相互作用和变化规律。结果表明：(1)在不去叶时,芦苇的叶绿素含量随着氮浓度的升高而升高,而互花米草的叶绿素含量随着氮浓度的升高出现先升后降的特点。在去叶条件下则正好相反,芦苇的叶绿素含量随着氮浓度的升高出现先升后降的特点,而互花米草的叶绿素含量则随着氮浓度的升高而升高。(2)芦苇在高氮下保持着持续的光合潜力,而互花米草在高氮下光合能力接近饱和。所以在自然条件下互花米草能够更有效利用光能,但芦苇保留着增加氮水平所具有的光合潜能。芦苇通过超补偿效应提高光合效率,而互花米草在去叶后,其光合效率有一定程度的降低。(3)互花米草在氮浓度增加时会降低株高,而将资源分配给叶片(同化器官)的生长,这可能会帮助互花米草在高氮下通过同化器官的资源投入比例而取得竞争上的优势。(4)随着营养成分的增加,芦苇会加大对叶(同化器官)和茎(支持器官)的资源投入,而减少对根(吸收器官)和根茎(觅养行为)的资源投入,这样会增加芦苇对高氮环境的适应,通过同化器官和支持器官的增加而取得竞争上的优势。(5)在中氮时,芦苇的无性繁殖最强烈,而当氮浓度继续增大时,芦苇会减少对无性繁殖器官的投入比例。互花米草的分蘖数和根状茎个数均随氮浓度的升高而增加,说明互花米草在营养充足的条件下,会增加对无性繁殖器官的资源投入,使自身的分布区得到扩展。(6)面对去叶干扰,互花米草会减少对有性繁殖的投入,这样可以将更多的资源用于无性繁殖。并且在氮资源充足的情况下,互花米草会减弱对有性繁殖的投入,而依靠无性繁殖迅速使分布区得到扩展。更多还原

【Abstract】 Currently, Phragmites australis are invading North American ecosystems which are dominated by Spartina alterniflora, in the meantime, S. alterniflora and their descendants are threatening Europe and China East Coast which P. australis is the dominate species. From a global perspective, these two species have similar regional characteristics of mutual-invasion. Therefore, investigate how environmental factors influence mutual-invasion mechanisms of S. alterniflora and P. australis have significant ecological values. Two factors (defoliation and nitrogen concentration) were selected to explore these mechanisms, from the perspective of simulating animal grazing and soil nutrient to measure the two species’interactions and variations. The results show that:(1) Without animal grazing, P. australis have stronger competitiveness than S. alterniflora. Otherwise, their competitiveness will be weakened, furthermore, S. alterniflora would take this opportunity to gain the growth advantages by improve their competitive power.(2) In a high nitrogen level, P. australis maintain sustained photosynthetic potential while the photosynthetic capacity of S. alterniflora is nearly saturated. Consequently, in natural conditions, S. alterniflora own higher efficiency in exploiting solar energy, however, P. australis retain the potential photosynthetic by increased nitrogen. P. australis has the ability to enhance photosynthetic efficiency by super compensation effects, whereas in the condition of defoliation, the photosynthetic efficiency of S. alterniflora has reduced to some extent.(3) In the condition of increasing nitrogen concentration, S. alterniflora will reduce its plant height in order to allocate resources to the growth of leaves(photosynthetic organs). This may help S. alterniflora to achieve competitive advantages by modulating the proportion of input resources in photosynthetic organs in a high nitrogen levels.(4) With the increase of nutrients, P. australis will improve the investments of leaf (photosynthetic organs) and stem (support organ) resources, meanwhile reduce those of root (uptake organ) and rhizomes (foraging behavior), in that case, an adaptation to high nitrogen condition will be improved, thereby to obtain a competitive advantage.(5) In a medium nitrogen level, P. australis have the strongest asexual reproduction, whereas with increasing nitrogen concentration, the proportion of investment in asexual reproductive organs will be reduced. On the contrary, S. alterniflora will raise those investments by increase the number of tillers and rhizomes.(6) In the condition of defoliation, S. alterniflora will convert their resource investments from sexual to asexual reproduction. The same situation will occur in a sufficient nitrogen environment as well.更多还原