180 resultados para Dominant plants

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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毛乌素沙地是中国半干旱地区典型沙地,这里的干旱生态系统对全球的水热配合格局的变化具有很灵敏的响应。随着未来全球气候变化,如温度和降水量变化,将给这里的陆地生态系统分布格局和生产力以及水分平衡带来巨大影响。故本文人工控制157. 5mm、315. Omm、472. 5mm和630. Omm4种施水量水平以及25/20℃和28/23℃(白天/晚上)两种温度,来研究与模拟毛乌素沙地优势植物对水分和温度变化的响应。 以沙柳、杨柴和油蒿幼苗为研究对象,人工控制4种降水量水平来探讨它们的水分平衡对全球变化中降水量变化的响应。结果表明,随着施水量的增加,沙地贮水量及其它的变化量、湿度、蒸发量和蒸腾量均逐渐增大。并且157. 5mm和315. Omm施水量的植物沙地出现水分亏缺现象。相同施水量下,沙地蓄水量和湿度均杨柴沙地>沙柳沙地>油蒿沙地,而植物蒸腾量却油蒿>沙柳>杨柴。 以沙柳和油蒿幼苗为研究对象,人工控制4种降水量水平来探讨植物气体交换过程对全球变化中降水量变化的响应。结果表明,施水量的增加显著提高了两种植物的净光合速率、蒸腾速率、气孔导度和光能利用效率,并且显著降低了叶片温度。同时,157. 5mm施水量造成沙柳和油蒿的净光合速率和蒸腾速率具有显著的“午睡”现象,而充足施水却有效的解除或缓解这种“午睡”现象。 以沙柳、杨柴、油蒿和柠条幼苗为研究对象,人工控制4种降水量水平来探讨植物叶绿素荧光对全球变化中降水量变化的响应。结果表明,不同施水量对这4种植物的初始荧光、最大荧光、可变荧光和PSII光化学效率均具有显著影响。157. 5mm施水量的沙柳、杨柴、油蒿和柠条以及630. Omm施水量的柠条出现明显的光抑制现象。 以沙柳、杨柴、油蒿和柠条幼苗为研究对象,人工控制4种降水量水平来探讨植物生长对全球变化中降水量变化的响应。结果表明,施水量的增加对沙柳、油蒿和杨柴枝叶形态和生物量等都具有显著正效应。而157. 5mm和630. Omrn的施水量对柠条生长具有负作用。另外,沙柳、杨柴和油蒿根冠生物量比随着施水量增加均逐渐减小,而不同施水量的油蒿根冠生物量比之间差异不显著。 以柠条、杨柴和油蒿幼苗为研究对象,人工控制两种温度水平来探讨植物形态、生物量和气候交换特征对增温的响应。结果表明,增温显著提高了柠条和杨柴株高、叶数、叶面积、生物量、净光合速率、蒸腾速率和气孔导度,却显著降低了水分利用效率。增温对油蒿叶数、叶大小、叶面积、生物量、蒸腾速率和气孔导度没有显著影响,却显著提高了油蒿的树高和净光合速率。柠条、杨柴和油蒿之间的种间生长和生理特征均有显著差异。

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浑善达克沙地是我国北方干旱半干旱区的主要沙地和严重荒漠化地区之一。同时也是我国内陆沙尘的主要源区之一。研究当地植物对沙地环境的适应方式有助于当地的荒漠化治理,加快生态环境恢复。本文应用(温室和野外)实验生态学方法研究了沙地植物对水分、沙埋和养分异质性环境的生态适应对策。 浑善达克沙地属于半干旱区域。在一次降雨过后,适合植物生长的湿沙层逐渐下降,或者说不适合植物生长的干沙层逐渐加厚。为了能够有效地从沙层中获得水分,植物的根系的伸长的速度必须大于湿沙层下降的速度。因此,当地分布的植物的根系则应该具有相应的形态、生长和生物量投资方面的可塑性。羊柴(Hedysarum laeve Maxim. (Leguminosae) )是当地的主要半灌木和固沙植物。我们研究了羊柴幼苗对不同土壤含水量和不同模拟降雨量的反应格局,以及移动沙丘生长季节的土壤含水量变动规律。发现,大于3%土壤含水量适合羊柴幼苗生长。最适土壤含水量为12%-20% 。在生长季节早期,羊柴幼苗比较容易在沙丘上定居。如果没有充分的后续降雨的话,萌发后的幼苗在沙丘顶部、落沙坡中部和后部定居比较困难。降雨量越大,根系越深、总根长越大、根系直径越大、侧根越多、根冠比越低。 在干旱半干旱区域的沙地,种子萌发的时间和地点对于植物的定居和存活具有关键作用。通过温室实验,研究了小叶锦鸡儿和羊柴的种子萌发和出苗对不同深度的沙埋的反应,及其与种子大小的关联。结果表明,小叶锦鸡儿和羊柴的种子萌发和出苗对浑善达克沙地的自然生境表现出相似的生态适应。这两个种的种子萌发的适宜温度为10-15ºC, 这是当地春季的平均温度。由于这两个种的种子萌发是光敏感的,所以它们的种子萌发受土壤含水量和光照强度二者之间的平衡调节。2 cm 的较浅沙埋最有利于种子萌发和出苗。种子埋得越深,种子的萌发率和出苗率越低,更多的种子受胁迫休眠保存在土壤中作为种子库。不同大小的种子的不同萌发能力也是一种重要的生态适应,这可以调节种子在合适的时间和合适的沙埋深度萌发和出苗。 冰草(Agropyron cristatum (L.) Gaertn)是浑善达克沙地植物群落中占优势的多年生根茎草本植物之一。种子在合适的地点和时间萌发以及幼苗在合适的地点和时间生长,对于冰草在沙地环境条件下生存和分布具有重要意义。本文研究了浑善达克沙地4-10月份土壤含水量变动情况和冰草种子萌发、出苗和幼苗生长对土壤含水量的响应。结果表明,4月下旬至5月上中旬的土壤含水量对冰草种子萌发、出苗和定居极为关键。控制条件下,冰草种子萌发的最适土壤含水量是12%-20%,出苗以及幼苗生长的最适土壤含水量是12%-16%。当土壤含水量低于3%,冰草种子不能萌发,土壤含水量低于6%时,幼苗不能出土和定居。当土壤含水量达到16%时,冰草幼苗生物量有所下降。在6%-8%的土壤含水量条件下,植株将更多的生物量投资于根的生长。 本文对浑善达克沙地低湿滩地、滩地-风沙沉积过渡区到风沙沉积区的赖草(Leymus secalinus (Georgi) Tzvel.)分株数、地上生物量、土壤水分和养分异质性进行了研究。结果表明,从低湿滩地、滩地-风沙沉积过渡区到风沙沉积区,随着土壤养分的降低,赖草分株数和地上生物量反而增加。赖草的分株数在三种生境中都存在空间自相关。并且,从低湿滩地、过渡区到风沙沉积区空间自相关的变程逐渐增加。地上生物量同样存在空间自相关,但变程以过渡区最大,风沙沉积区最低。土壤水分仅仅在风沙沉积区存在空间自相关。在三种生境条件下,土壤全氮和有机质的空间分布格局相似,都在低湿滩地和过渡区存在空间自相关且变程相似。在风沙沉积区不存在空间自相关。赖草的空间分布格局在低湿滩地为偏离随机适度聚集的分布格局,在过渡区近似于聚居分布,而在风沙沉积区为均匀分布格局。 豆科锦鸡儿属(Caragana )植物因其可以生物固氮而在草原生态系统当中具有特殊的地位。定量分析小叶锦鸡儿(Caragana microphylla )灌丛在浑善达克沙地不同生境条件下的分布格局,有助于理解植被与土壤养分循环之间的关系和合理制定退化沙地的恢复对策。本文采用地统计学中的半方差分析和分形分析两种方法研究了浑善达克沙地小叶锦鸡儿灌丛的空间分布格局,分析了不同生境中小叶锦鸡儿灌丛的植被、土壤水分和养分间的相关性。结果表明(1)小叶锦鸡儿灌丛在三种生境条件下(滩地、固定沙丘和半固定沙丘)的盖度、土壤有机质和全氮的空间分布符合球状模型,空间自相关显著;(2)土壤pH值在滩地和固定沙丘的空间分布符合球状模型且空间自相关显著,但在半固定沙丘空间自相关不显著;(3)土壤水分在三种生境中的空间分布都符合线性模型,空间自相关显著。(4)植被的变异尺度(变程)小于各个土壤要素的变异尺度。植被(小叶锦鸡儿灌丛)的分布和形成过程决定了土壤养分的分布和形成过程。当地的豆科植物在养分“沃岛”现象的形成中起了重要作用,合理的利用和布局当地的豆科植物,可以更加有效地补充草地生态系统的养分,从而有利于加快当地生态系统的恢复进程。

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The performance of a wetland system in treating lead (Pb)/zinc (Zn) mine drainage was evaluated by using the polyurethane foam unit (PFU) microbial community (method), which has been adopted by China as a standardized procedure for monitoring water quality. The wetland system consisted of four cells with three dominant plants: Typha latifolia, Phragmites australis and Paspalum distichum. Physicochemical characteristics [pH, EC, content of total suspended solid (TSS) and metals (Pb, Zn, Cd, and Cu)] and PFU microbial community in water samples had been investigated from seven sampling sites. The results indicated that the concentrations of Pb, Zn, Cd, Cu, and TSS in the mine drainage were gradually reduced from the inlet to the outlet of the wetland system and 99%, 98%, 75%, 83%, and 68% of these metals and TSS respectively, had been reduced in concentration after the drainage passed through the wetland system. A total of 105 protozoan species were identified, the number of protozoa species and the diversity index (DI) gradually increased, while the heterotrophic index (HI) gradually decreased from the inlet to the outlet of the wetland system. The results indicated that DI, HI, and total number species of protozoa could be used as biological indicators indicating the improvement of water quality.

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Studies of abundance, diversity and distribution of antibiotic-resistant bacteria and their resistance determinants are necessary for effective prevention and control of antibiotic resistance and its dissemination, critically important for public health and environment management. In order to gain an understanding of the persistence of resistance in the absence of a specific antibiotic selective pressure, microbiological surveys were carried out to investigate chloramphenicol-resistant bacteria and the chloramphenicol acetyltransferase resistance genes in Jiaozhou Bay after chloramphenicol was banned since 1999 in China. About 0.15-6.70% cultivable bacteria were chloramphenicol resistant, and the highest abundances occurred mainly in the areas near river mouths or sewage processing plants. For the dominant resistant isolates, 14 genera and 25 species were identified, mostly being indigenous estuarine or marine bacteria. Antibiotic-resistant potential human or marine animal pathogens, such as Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and Shewanella algae, were also identified. For the molecular resistance determinants, the cat I and cat III genes could be detected in some of the resistant strains, and they might have the same origins as those from clinical strains as determined via gene sequence analysis. Further investigation about the biological, environmental and anthropogenic mechanisms and their interactions that may contribute to the persistence of antibiotic-resistance in coastal marine waters in the absence of specific antibiotic selective pressure is necessary for tackling this complicated environmental issue.

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In the present talk, the simulation of vortex dominant and turbulent flows are primarily addressed. To cope with complicated circumstances in environmental flows we illustrate the strategy of combining simplified physical model and suitable algorithm by a few examples.

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