【作者】 唐龙；

【导师】 李博； 赵斌；

【作者基本信息】 复旦大学 ， 生态学， 2008， 博士

【摘要】 生物入侵是当前全球最棘手的三大环境问题之一。其中,外来植物入侵已经造成了严重的生态、经济和社会后果,人们迫切希望找到能有效控制入侵植物,包括治理入侵植物和恢复受损生态系统的高效、经济且环境友好的方法。本研究以互花米草(入侵植物)以及芦苇(土著植物)为例,在上海崇明东滩盐沼开展了为期3年的野外实验和受控实验,探讨了刈割、淹水和芦苇替代综合途径治理互花米草,恢复土著种芦苇的可行性及其相关的生态学机制,同时研究了入侵植物控制过程中的生境依赖性问题,旨在为该入侵种的有效治理提供科学依据。本研究得出的主要结论如下:(一)崇明东滩的生境有较大的空间异质性。在不同区域,持续淹水时间与土壤孔隙水盐度差异较大,这种差异能引起刈割互花米草的治理效率和种植芦苇的恢复效率随生境的异质性而发生变化。互花米草刈割当年的治理效率与第二年的持续效果随着持续淹水时间的延长而提高,且持续效果随盐度的降低而提高;种植芦苇当年与第二年的生长状况随盐度的降低而得到改善,且第二年的生长随着持续淹水时间的延长而得到促进,说明入侵植物控制效率存在生境依赖性。(二)持续淹水时间是决定刈割互花米草再生长能力的关键环境因子。淹水造成的缺氧胁迫,导致刈割互花米草根系有氧呼吸关键酶葡萄糖-6-磷酸脱氢酶的活性随着淹水时间的延长而降低直至完全失活,而在此过程中无氧呼吸的两种关键酶乙醇脱氢酶和乳酸脱氢酶的活性同样逐渐降低直至失活,最终表现为互花米草根系完全失去活力。这说明刈割法治理互花米草效率的生境依赖性源自互花米草再生长能力对淹水时间的响应。随着淹水持续时间的延长,被刈割互花米草的再生长受到抑制,达到一定程度,将导致刈割互花米草死亡,因此,刈割法适用于低潮区或长期淹水的区域,而短淹水区域则应该寻找其它治理措施,或依据入侵斑块的淹水时间适当地调整刈割策略,有条件的地区可以采取相应的工程措施局部改变淹水时间,以提高入侵区域互花米草治理的整体效率。(三)土壤孔隙水盐度是决定芦苇生长的重要环境因子。芦苇的净光合作用速率、蒸腾速率以及气孔导度对盐度非常敏感,并随着盐度的增加而降低;而入侵植物互花米草的净光合作用速率与蒸腾速率等在整个生长旺盛期可在不同盐度环境中保持较高的水平。导致这种差异的原因是互花米草不仅能够将钠离子排除在主要的生理过程之外,同时随着盐度的升高,该入侵植物可以将影响光合作用与蒸腾的镁离子与促进光合与蒸腾的钾离子维持在基本恒定的水平。这不仅降低了钠离子的毒害,同时还在较大的盐度范围内保证了生产、运输等生理过程的活性。相反,随盐度升高而浓度显著增加的钠离子直接影响了芦苇的蒸腾等生理过程,且体内可促进光合及蒸腾作用的镁离子与钾离子的浓度随盐度的升高而降低。这不仅导致了盐离子对芦苇的毒害,而且使得其生产、运输等生理活动随着盐度的升高而降低:当盐度超过8ppt,芦苇将在与互花米草的竞争中处于劣势;当盐度超过10ppt,芦苇不能有效地完成有性繁殖;当而盐度超过15ppt,种植芦苇分株死亡率达到50%;而互花米草的生长、繁殖以及根茎贮藏状况则可在模拟实验涉及的0～20ppt盐度范围内保持着良好的表现。这些说明只有在生境盐度保持在8ppt以下时,才有可能恢复芦苇群落。因而,建议在盐度较低的区域以芦苇为主要的恢复目标种,而盐度较高区域的恢复目标种,则应在更为耐盐的土著植物中选取,或者采取必要的措施适当的降低恢复区域的盐度,以提高入侵区域恢复的整体效率。同时,互花米草可在盐度较大的范围内,保持着较强的再入侵力,因而在土著植被恢复的过程中,适时监测并采取补救性治理措施是必要的。需要指出的是,本研究仅以刈割法为物理措施的代表研究了治理效率的生境依赖性,为了更全面地认识入侵植物治理效应的生境依赖性,化学法、生物控制法以及综合控制法治理效率的生境依赖性及其机制仍值得进一步研究;另一方面,虽然本研究仅以种植芦苇的方式研究了土著植物恢复效率的生境依赖性,但是恢复实践中还应该考虑生态系统要素、结构以及功能恢复的生境依赖性。更多还原

【Abstract】 Biological invasion is one of the most serious environmental problems of the world. Exotic plant invasions have caused severe ecological, economical and social consequences. China is heavily invaded by an array of exotic plants, so to effectively control invasive exotic plants is now an urgent task. This study used invasive Spatina alterniflora as the model plant and clipping as control method to experimentally examine habitat dependence of clipping control efficiency of invasive Spartina alterniflora. The major aim of this study was to illustrate how the control efficiency of Spartina through clipping can be enhanced through altering flooding and salinity in the environments, i.e. the habitat-dependence of the control efficiency. As an important component of the Spartina control, resotring native plant, Phragmites australis, was also experimentally explored in relation to the habitat characteristics. In so doing, field manipulative experiments and common garden experiments were performed in this study; and the main results obtained are summarized as follows:（1） There were significant differences in persistent flooding time and soil pore water salinity among the different sites in Chongming Dongtan estuary salt marsh, which caused varying control efficiency of Spartina alterniflora and differing recovery efficiency of Phragmites australis under the same experimental treatment. The control efficiency of Spartina alterniflora through clipping in the first year and the persistent efficiency in the following year increased with the increase of persistent flooding time, while the efficiency in the second year increased with the decrease of salinity. The growth of transplanted Phragmites australis in clipped Spartina alterniflora patches was promoted by lower salinity in both the first year and the second year, while the growth in the second year was stimulated by prolonged flooding time. The results showed that the control efficiency of invasive plants was habitat dependant.（2） Persistent flooding time was the major determinant of the control efficiency of Spartina alterniflora through clipping. The regrowth of clipped Spartina alterniflora decreased with the increasing flooding time, and Spartina alterniflora eventually died when the flooding time exceeded the threshold. Thus clipping control could be applicable to the low marsh or areas that are persistently flooded. The mechanism of this damage caused by flooding is that the oxygen availability, and the activity of key enzyme Glucose-6-phosphate dehydrogenase of Spartina alterniflora aerobic respiration decreased with the increasing flooding time until complete inactivation, i.e., inactivation of Spartina alterniflora roots. Thus, it was the response of Spartina alterniflora to the flooding time that caused the dependence of the control efficiency on the habitat properties. Therefore, it is practical to apply clipping in persistent flooded areas while other control methods should be considered in other areas with no persistent flooding. Clipping regime needs to be desgned in relation to to the flooding time of invaded areas so as to improve the whole control efficiency.（3） Substrate salinity is the physical determinant of recovery efficiency of ecological replacement. When salinity exceeded 15ppt, ramet mortality rate of tranplanted Phragmites australis reached about 50%, making its population establishment unlikely. When salinity exceeded 10ppt, Phragmites australis could not complete its sexual reproduction, making the transplanted population unable to expand rapidly. When salinity exceeded 8ppt, Phragmites australis was competitively inferior to Spartina alterniflora, which made the transplanted Phragmites australis subject to reinvasion by Spartina alterniflora. On the other hand, the target species Spartina alterniflora did not considerably change its growth, reproduction and storage under the experimental salinity range. This resulted in the decrease of recovery efficiency of native plant and the increase of reinvasion probability of Spartina alterniflora with the increasing salinity. Thus it can be seen that the development of transplanted Phragmites australis population would reach the expected goal only if the habitat salinity was lower than 8ppt. The effects of salinity on recovery efficiency are the result of the difference in tolerance to salt stress between Phragmites australis and Spartina alterniflora. Net photosynthetic rate, transpiration rate and stoma conductivity of Phragmites australis were sensitive to salinity, decreasing with the increasing salinity. Net photosynthetic rate and transpiration rate of Spartina alterniflora were maintained at a high level during its growing period. The reason was that Spartina alterniflora could exclude the salt ions from its main physiological processes, and maintain Mg²⁺ （which affects photosynthesis and transpiration） and K⁺ （which promotes photosynthesis and transpiration） content at a relatively stable level although the salinity increased. This not only reduced the damage by Na+ but also ensured the basic physiological processes such as photosynthesis and transportation within a wide salinity range. On the contrary, Na+ affected transpiration of Phragmites australis directly; and Mg²⁺ and K⁺ contents decreased with the increasing salinity. This not only caused the damage by salt ions, but also led to the reduction of photosynthesis and transportation with the increasing salinity. As a result, Phragmites australis could be used for restoration of fresh and brackish areas, whereas other native halophytes should be considered in saline habitats.This study explored the possibility of using physical control and ecological replacement methods to mange Spartina alterniflora at Chongming Dongtan in the Yangtze River estuary. In order to design sound control regime for invasive plants, habitat dependence of the efficiency of chemical, biological and integrated control methods needs to be studied further.更多还原