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The aim of this work is to study the temporal dynamics of rhizome epiphytes and sessile animals living on the rhizomes of the seagrass Posidonia oceanica in the east of Tunisia. Surveys were conducted in October 2009, and in January, April and August 2010 on a fringing reef located in Chebba. Rhizomes were sampled by SCUBA diving at three stations. Samples were examined with a microscope to estimate the cover of macroinvertebrate and macroalgal organisms on the top 10 cm of each rhizome. Results revealed a high diversity of epiphytes on P. oceanica rhizomes with a dominance of red and brown algae, ascidians, and bryozoans. Distinct temporal changes were observed in Oued Lafrann, with a high January cover (winter period) for all groups. These winter increases can be attributed to: (i) the low phenological parameters of P. oceanica in winter that reduce the effects of shading, (ii) life cycles of the epiphytes and invertebrates, (iii) water motion and (iv) grazing. 相似文献
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Transplant trials of the seagrass Posidonia australis were carried out after loss of seagrasses following eutrophication and increased turbidity in two marine inlets on the south coast of Western Australia. A pilot study in Oyster Harbour measured survival and growth in situ for 4 years. Long-term survival rates were high (96–98%), providing plants were anchored into the sediment. All unanchored plants were lost in the first winter. Following the success of the pilot study, a more comprehensive program began 3 years later with over 500 transplant units collected from either actively growing edges of nearby patches (plagiotropic growth form) or within established meadows (orthotropic growth form). Transplant units from edges expanded at a faster rate compared to units from mid-meadow but increases in shoot numbers were similar. Growth rates in the first 2.5 years averaged 10–20 cm yr−1 horizontal rhizome extension, depending on the source of the transplant units, and 4–12 shoots per initial shoot yr−1, depending on the initial shoot number of the transplant unit. After 5 years, shoot numbers of individual transplants were similar to shoot densities recorded for natural meadows, >500 shoots m−2. Approximately, 10% of transplants from mid-meadow flowered in the first year, whereas transplants from edges flowered only after 5 years. 相似文献
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科尔沁沙地典型生境下芦苇的生长特征分析 总被引：3，自引：3，他引：0
对科尔沁沙地两类典型生境下芦苇根茎生长及生物量等特性进行了分析研究。结果表明,固定样地芦苇株高、分蘖株数、不定芽数、根茎节数及根茎总长均大于半流动样地。从半流动样地到固定样地,芦苇根茎表现出节间长度缩短,节间直径变粗的趋势。固定样地芦苇叶长、叶宽明显大于半流动样地,并且固定样地芦苇叶间距是半流动样地上的近3倍。与半流动样地相比,固定样地根茎生物量在总生物量中所占比例有所增加,而地上生物量所占比例减小。芦苇根茎生长及生物量分配在两类样地间的变化特征与土壤质地、紧实度以及养分含量等因素有密切的联系,同时也反映了芦苇对不同沙生生境的适应对策。 相似文献
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The aim of the present study was to evaluate whether the variability in the structure of the epiphytic assemblages of leaves and rhizomes of the Mediterranean seagrass Posidonia oceanica differed between depths at a large spatial scale. A hierarchical sampling design was used to compare epiphytic assemblages at two different depths (10 and 20 m) in terms of both species composition and abundance and patterns of spatial variability in the Tuscan Archipelago (North Western Mediterranean Sea, Italy). Results showed significant differences in the structure of assemblages on rhizomes and leaves at different depths. These differences were related to species composition and abundance; differences were not significant for total biomass, total percentage cover and percentage cover of animals and algae. Whereas the higher variability was observed among shoots in all the studied systems, patterns of spatial variability at the other spatial scales investigated differed between the two studied depths. Moreover, in the present study, analogous patterns between depths resulted for both the assemblages of leaves and rhizomes, suggesting that factors that change with depth can be responsible for the spatial variability of both the assemblages (leaves and rhizomes), and operate regardless of the microclimatic conditions and the structure of assemblages. 相似文献
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根茎是植物显著变异的地下茎,对于研究湿地克隆植物的结构功能、生长繁殖、入侵生态与进化生态等具有重要价值。根茎适应水文情势和基质养分的变化,并在本地竞争与向外入侵中表现出了显著的可塑性且具有种间差异。对于特定物种而言,根茎的内在特质反映了其所处的环境特征,而根茎生长的可塑性则显示出适应周围环境短期变化的能力。根茎与微生境之间的相互关系体现了生物与环境之间在构件尺度的协同演化过程。迄今为止的研究涵盖了根茎的生理生态诸方面,但根茎对于植物的结构、功能、生长与繁殖之间密切联系所承担的适应性角色还缺乏深入理解。在综述目前对湿地克隆植物根茎表形可塑性研究的基础上,探讨了根茎在湿地植物研究中亟待加强的特殊地位及其作为可塑性研究的模式构件的潜力,并提出了未来研究的若干方向。 相似文献
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