上海城市废弃地杂草种子库季相动态与城乡差异

发布时间：2018-01-18 02:36

本文关键词：上海城市废弃地杂草种子库季相动态与城乡差异　出处：《华东师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：快速城市化引发的生境退化、外来种入侵等生态环境问题,对城市植物多样性产生了诸多影响。杂草作为城市植被的三大组分之一,具有对异质化生境敏感性高、可塑性强及适应对策多样的特点,是研究城市化对植被影响及其响应的模式对象。探究其土壤种子库在城乡梯度上的差异,及其与地上杂草群落间的关系,有助于揭示城市化对杂草物种多样性的影响。本研究以上海废弃地杂草土壤种子库为研究对象,在城区-城郊-郊区城市化梯度上,选取24个样地进行春秋两季的群落学调查,并采集土壤开展种子库萌发实验,进而分析杂草土壤种子库的种类、密度、物种多样性的城乡差异,比较其与地上杂草群落物种组成的相似性。主要研究结果如下:1)上海城市废弃地杂草种子库以一年生(尤其是夏季一年生)、低矮类型、乡土种为主;秋季的种子密度(2675粒/m2)远高于春季(838粒/m2)。在城区-城郊-郊区梯度上,一年生比例、低矮类型比例均呈现增加趋势,而种子密度和外来种的比例(约40%)无明显城乡差异。2)上海城市废弃地杂草土壤种子库和地上杂草群落的丰富度和Shannon-Wiener 指数在城乡梯度上均无明显差异。其中地上群落春季的丰富度和Shannon-Wiener指数分别为32种和3.0,秋季分别为22种和2.6;土壤种子库春季的丰富度和Shannon-Winener指数分别为11种和2.0,秋季分别为8种和1.7。3)上海城市废弃地杂草土壤种子库物种组成与地上群落间存在显著差异。以Jaccard系数表征物种相似性,春季地上植被群落与地下土壤种子库间,城区(0.14±0.06)显著低于城郊(0.24±0.08);秋季地上植被与春季地下土壤种子库间,城区(0.09±0.06)显著低于郊区(0.17±0.06)。4)上海城市废弃地杂草的物种组成,无论在土壤种子库还在地上群落,均表现出明显的春秋季节差异。春秋两季间的相似性(Jaccard系数)均在2.5以下,并且土壤种子库春秋两季的相似性(0.11±0.05)在城区显著低于地上群落(0.20±0.03)。这表明高度的城市化导致了地下地上间在季相变化上的不同步。综上所述,上海城市废弃地杂草种子库以低矮型和夏季一年生为主。人为干扰导致的较高外来种比例以及土壤种子库与地上群落间的低相似性,使得城市化这一个综合环境因子对废弃地杂草土壤种子库的影响并不显著。
[Abstract]:Ecological and environmental problems, such as habitat degradation and alien species invasion, caused by rapid urbanization, have a lot of impacts on urban plant diversity. Weeds are one of the three major components of urban vegetation. It has the characteristics of high sensitivity to heterogeneous habitats, strong plasticity and various adaptive strategies. It is a model object to study the effects of urbanization on vegetation and its response. The difference of soil seed bank in urban and rural gradient is explored. The relationship between the weed community and the above ground weed community is helpful to reveal the effect of urbanization on weed species diversity. This study took the weed soil seed bank of Shanghai abandoned land as the research object. On the gradient of urbanization, 24 plots were selected for community investigation in spring and autumn, and seed bank germination experiments were carried out, and the species and density of weed soil seed bank were analyzed. The differences of species diversity between urban and rural areas were compared with the species composition of aboveground weed community. The main results were as follows: 1) the annual (especially summer annual) weed seed bank in abandoned land of Shanghai. Low type, native species mainly; The seed density of 2 675 seeds / m2 in autumn was much higher than that in spring (838 seeds / m2). The ratio of seed density to exotic species (about 40%) has no significant difference between urban and rural areas. Richness and Shannon-Wiener of Weed soil seed Bank and aboveground Weed Community in abandoned Land of Shanghai. There was no significant difference in the index between urban and rural areas, and the richness and Shannon-Wiener index of aboveground community in spring were 32 species and 3. 0 respectively. 22 species and 2.6 species in autumn; The richness and Shannon-Winener index of soil seed bank in spring were 11 and 2.0 respectively. There were significant differences between species composition of weed soil seed bank and aboveground community in Shanghai. Jaccard coefficient was used to characterize species similarity. Between the aboveground vegetation community and soil seed bank in spring, 0.14 卤0.06 in urban area was significantly lower than that in suburban area (0.24 卤0.08). The species composition of weeds in urban area was significantly lower than that in suburban area (0.17 卤0.06) between autumn and spring soil seed bank (0.09 卤0.06). No matter the soil seed bank is still in the aboveground community, there are obvious seasonal differences in spring and autumn, and the similarity of Jaccard coefficient between spring and autumn is below 2.5. The similarity of soil seed bank in spring and autumn was 0.11 卤0.05) in urban area, significantly lower than that in aboveground community (0.20 卤0.03). This indicates that the high degree of urbanization leads to the inconsistency of the seasonal changes between the ground and the ground. The weed seed bank in the abandoned land of Shanghai is dominated by low type and annual growth in summer. The proportion of exotic species caused by human disturbance and the low similarity between soil seed bank and aboveground community are higher. The effect of urbanization, a comprehensive environmental factor, on weed soil seed bank in abandoned land was not significant.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S451

【参考文献】