2 resultados para lawn tennis
em Chinese Academy of Sciences Institutional Repositories Grid Portal
Resumo:
某些克隆植物通过克隆整合能够很好的适应逆境或快速扩张。基于克隆整合,研究克隆植物的抗逆性、入侵性及其对群落结构的影响在很多方面值得深入。本文主要应用实验生态学的方法,分别在野外或温室以沙鞭、空心莲子草和羊柴为主要研究对象,研究克隆整合对处于逆境生长条件下克隆植物生长的影响;克隆整合对入侵植物竞争力和被入侵植物群落组成的影响;克隆整合对沙地群落结构和初级生产力的影响,探讨克隆植物对风蚀和水淹的适应机制、入侵克隆植物的入侵机制以及对群落组成和结构的影响机制。主要结论如下: 1. 沙鞭分株的叶片数目和生物量跟沙鞭根状茎的埋藏深度高度正相关,当根状茎被暴露在空气中时,上面所依附的分株要么死亡,要么长势很弱。每样方内沙鞭的分株数目、叶片数目和总生物量随风蚀强度的增加而降低。在对照和短期风蚀中,根状茎连接并不影响上述指标,但是在长期风蚀下,根状茎连接的作用会增强。根状茎连接能够减轻风蚀对沙鞭的负面影响,这很有可能是因为遭受风蚀胁迫的分株从那些没有遭受风蚀侵害的分株那里获得了水分和光合产物的资助。本研究首次证实了保持根状茎连接有助于提高干旱区植物抵御风蚀的能力。 2. 水淹会降低空心莲子草先端分株的生长;克隆整合显著增强了空心莲子草先端分株的生长和繁殖,但降低了基端分株的生长和繁殖。最终,克隆整合并不影响整体空心莲子草克隆片段的生长表现,这预示当空心莲子草从陆地生境向水生生境扩散时,克隆整合对其总体没有净收益。我们认为空心莲子草在由陆地扩张到水域时,可能拥有一种“双刃剑”机制:当处于水生生境中的先端分株得到处于陆生生境中的基端分株的资源支持时,先端分株能够增强自身生长;当因外界扰动导致二者间相连匍匐茎断裂后,陆生生境中的基端分株能够快速增强自身的匍匐茎和分株生长。这种机制可能使得空心莲子草很好的适应高度干扰或高度异质生境,从而增强了其入侵性。 3. 竞争显著降低了空心莲子草先端分株的光系统II中的最大量子产额(Fv/Fm)和生长(生物量、分株数目、叶片数目、总匍匐茎长度和总叶面积),但并不影响高羊茅的生物量。匍匐茎连接显著增强了空心莲子草先端分株的最大量子产额和生长。然而,这种连接效应在竞争时的作用要比非竞争时的作用小的多,而且匍匐茎连接并没有改变空心莲子草的相对邻体效应。与非竞争环境相反,在竞争条件下匍匐茎连接会降低空心莲子草对根系的生物量投资。克隆整合可能对提高空心莲子草的竞争力帮助不大,但是对其开拓空旷领地却非常重要。这些结果预示空心莲子草的入侵性可能和其克隆整合作用有密切关系。 4. 克隆整合显著增强了空心莲子草在群落中的扩张能力,但并没有提高其抑制整体群落物种的能力。相比低密度播种群落,生长在高密度播种群落中的空心莲子草长势明显要弱,高密度播种群落具有更强的抵御入侵的能力。在低密度播种群落中,相比切断群落内外空心莲子草相连匍匐茎,如果保持其连接,优势物种的地上生物量会降低而次优势物种的地上生物量会增加,进而群落的丰富度会得到提高。实验结果预示克隆整合能够增强入侵物种在建植群落中的扩张速度,并能够修饰其在群落结构上的影响,改变群落中单个物种的生长表现。 5. 克隆整合显著增强了羊柴在沙地植物群落中的分株数目,但并没有提高其地上生物量。羊柴分株数目的变化受不同处理因素的影响,在加氮的处理中分株数目为最大,切断处理中为最小。在群落主要组成物种中,克隆整合显著影响了烛台虫实的地上生物量,而其它主要物种的地上生物量则不受处理因素影响。克隆整合并没有影响沙地群落的物种多样性,但会显著影响沙地群落的初级生产力,尤其是添加氮肥以后。
Resumo:
Data of classification, origin, pathway and environmental impacts of invasive alien micro-organisms, invertebrates, amphibians and reptiles, fish, birds, mammals, weeds, trees, and marine organisms in terrestrial, aquatic and marine ecosystems of China, were analyzed, based on literature retrieval, field survey and consultation. Some 283 invasive alien species were recorded in China, including 19 invasive alien micro-organisms, 18 aquatic plants, 170 terrestrial plants, 25 aquatic invertebrates, 33 terrestrial invertebrates, 3 amphibians and reptiles, 10 fish, and 5 mammals. Of the invasive alien species, 55.1% originated from North and South America, 21.7% from Europe, 9.9% from Asia, 8.1% from Africa and 0.6% from Oceania. Many institutions and individuals in China lack adequate knowledge of ecological and environmental consequences caused by invasive alien species, with some ignorance of the dangerous invasion in the introduction of alien species. For instance, 50.0% of invasive alien plants were intentionally introduced as pasture, feedingstuff, ornamental plants, textile plants, medicinal plants, vegetables, or lawn plants, 25% of alien invasive animals were intentionally introduced for cultivation, ornament, or biological control, In addition, more efforts are being made in the introduction of alien species, and little attention is paid on the management of introduced alien species, which may cause their escape into natural environment and potential threats to the environment. There were also gaps in quarantine system in China. All microorganisms were unintentionally introduced, through timber, seedling, flowerpot, or soil; 76.3% of alien invasive animals invaded through commodity or transportation facility because of the failure of quarantine. Therefore, quarantine measures should be strictly implemented; and meanwhile the intentional introduction of alien species should be strictly managed and a system of risk assessment should be implemented.