| 题名 | 北京东灵山草本植物多样性海拔格局机制研究 |
| 作者 | 蒋子涵 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-12 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 马克明 |
| 关键词 | 草本群落，功能属性与多样性，α与β多样性，海拔多样性格局，系统多样性，系统发育树结构，贝叶斯物种分布模型。 Bayesian evolutionary model, Biogeography, Elevational richness pattern, Functional diversity, Functional traits, Phylogenetic diversity |
| 其他题名 | A study about mechanisms of herb elevational richness pattern: integrating ecological and evolutionary processes |
| 中文摘要 | 物种多样性的海拔分布格局一直是生态学的热点研究问题，不仅因为山地生态系统具有较高的多样性，同时海拔梯度也提供了一个研究动植物对环境变化响应的完美平台。由于环境因子沿海拔梯度的变化规律与纬度梯度相似，因此科学家认为其多样性格局也应与纬度梯度相近。但许多研究结果表明两者存在很大不同：多样性海拔梯度的峰值往往出现在中海拔。虽然有关单峰型多样性格局存在有大量的研究和假说，但原因仍不清楚。本文研究结合植被调查、功能属性、系统发育多样性以及贝叶斯模型，旨在对草本植物多样性海拔格局进行描述和解释。 本文研究地位于北京东灵山地区，海拔1000到2300 m, 植被类型为辽东栎为主的阔叶林。利用样带调查法进行植被基础调查，记录乔木，灌木，草本植物的多度，盖度和种类，共调查142个样方。在海拔梯度上每隔25m设置3个1×1 m的草本样方，调查样方内所有草本植物的叶片厚度，硬度，大小，绒毛密度，比叶重，单位面积的氮含量。利用Phylomatic数据库构建系统发育树，计算每个样方的系统发育多样性。在海拔尺度上每隔50 m设置一个土壤温度检测器，每隔15分钟记录一次数据。调查每个样方的土壤环境数据：土壤有效氮，土壤有效磷，土壤pH, 土壤有机质，土壤含水量。分析结果如下： (1) 草本物种多样性的海拔格局呈现单峰型，其最大值出现在1800 m左右，灌木和乔木的多样性随着海拔的升高而降低，树线出现在1750 m左右。 温度因子(最低，最高温度，年均温)和山体面积表现出了显著的单峰型海拔格局，与生产力相关的潜在蒸发量随着海拔的升高逐渐降低，而土壤有效氮和有效磷随海拔的升高而升高。 (2) 利用广义混合模型(GMM)研究上层木对草本群落的影响，结果表明上层木的盖度显著影响了草本群落的多度和高度，但对多样性的影响却随着海拔的变化而变化，即在低海拔地区促进了草本多样性在高海拔地区又起到了抑制作用。 最高温度显著降低了草本多样性，但对草本高度和多度影响不显著。沿海拔梯度群落组成发生显著变化，低海拔地区耐旱种为优势物种，随着海拔升高其优势度逐渐降低。 (3) 广义线性模型的结果显示对草本多样性影响最大的两个因子是极端温度，将样带分为两部分：底部样带(1000-1800 m)与顶部样带(1800-2300 m)，结果表明不同样带的驱动因子有所不同：对于底部样带来说，多样性主要受到高温影响，而对于顶部样带，霜期的长短是其多样性的主要决定因素。对功能和系统发育多样性的分析也得到了同样的结果，基于比叶重和叶片大小的功能多样性受到了极端高温的影响，而基于绒毛密度和叶片厚度的功能多样性受到了霜期长短的影响。 (4) 我们对物种分布模型(SDM)加以改进，考虑了不同海拔段物种面临的灭绝压力(温度升高时温度高海拔物种所面临的灭绝压力，温度下降时低海拔物种所面临的灭绝压力，扩散限制导致的灭绝压力)以及生态位进化，重新构建了一个结合生态与进化过程的模型，利用EPICM数据库的温度变化数据对物种沿海拔分布变化进行拟合，结果表明：物种在中海拔灭绝率显著低于高海拔或低海拔，原因是当温度升高时高海拔物种面临较高的灭绝压力，而温度降低时低海拔物种面临较高的生存压力。但这种中海拔优势受到物种进化率的影响，当进化速率较高时，物种的多样性格局只受初始迁移位置决定。 本研究利用功能属性和多样性，系统发育多样性和贝叶斯模型作为研究工具，旨在揭示草本多样性海拔格局的驱动因子，结论如下： (1) 种间作用对草本多样性没有直接的影响，但是其显著改变了群落结构。 (2) 极端温度是导致单峰型多样性海拔格局的主要原因。由于低海拔地区的温度较高，高海拔地区的温度较低，而中海拔地区有最适宜的温度和，所以拥有最多的物种。 (3) 物种最初的移居位置并不一定是形成单峰型海拔多样性格局的主要原因，会受到物种灭绝率和进化速率的限制，当进化速率较高时，单峰型海拔格局主要取决于初试移居地。中海拔由于地理位置的特殊，可以在环境改变时向上或者向下移动，从而缓冲环境变化带来的影响。我们认为单峰型海拔多样性格局的原因并不是因为物种最先迁移到中海拔，而是因为中海拔物种的灭绝率最低。 |
| 英文摘要 | Many biologists have been fascinated in particular by observations of species richness changes along elevational gradients, as these have proven to be useful platforms from which to research the effects of environmental change on mechanisms of species coexistence. It was long believed that the richness patterns along elevational gradients should reflect the latitudinal pattern, because the environmental variation across elevations was similar to that of the latitudinal gradient. However, many studies have shown that a large number of taxa exhibit their greatest richness at intermediate elevations. Many studies try to explain this phenomenon, however, the underlying reasons still very clear.In this study, we used the functional diversity, phylogenetic diversity and a Bayesian evolutionary model to access the underlying reason of herb elevational richness pattern. Our study area in Dangling mountain, located in southwest of Beijing. The elevational gradient from 1020 to 2300 m, its natural vegetation consists of highly heterogeneous, warm, temperate zone, deciduous broad-leaved forest. We surveyed 12 transects on a continuous elevational gradient. We divided 12 transects into 142 plots, each 10×10 m2. Within each plot, the abundance, height and DBH of overstory-layer species (height > 3.0 m) be recorded, three subplots were selected randomly for the herbaceous inventory; every species in the subplots was recorded. We also collected the functional traits as: leaf hardiness, leaf area, leaf thickness, leaf mass per area and hair density. We calculated the phylogenetic diverisity by Phylomatic 2.0. We measured the soil temperature, soil moisture, soil nitrogen availability, soil phosphorus availability and soil pH along the elevational gradient. The results as below: We employed GMM to detect the relationship among over-story species cover, herb species and temperature. The result showed that the cover from over-story species significant change the abundance and height of herb species, but the impacts on richness is varied along the elevational gradient: at low elevations, the cover from over-story species promote the herb richenss, whereas at high elevations, the cover reduce the herb richness. Temperature in non-gaps being cooler than in forest gaps, and overstory cover show a positive relationship with herb abundance. We found that the period of high temperature (> 35℃) was the best predictor of herb richness below the timberline, while the frost period was the best predictor for herb communities above the timberline. Phylogenetic diversity peaked at intermediate elevations, suggesting that herb species suffer more abiotic stress at lower and higher elevations. Individual trait functional diversity analyses showed that functional traits related to drought tolerance (leaf mass per area, leaf area) exhibited positive relationships with elevation, while functional traits related to freezing tolerance (leaf hardiness and hair density) exhibited negative relationships. We constructed a geographical range-based, stochastic simulation model that incorporates speciation, evolution, niche conservatism, range shifts and extinctions under late Quaternary temperature cycles along elevational gradients. In the model, elevational patterns of species richness arise from the differential survival of founder lineages, consolidated by speciation and the inheritance of thermal niche characteristics. The model yields a surprisingly rich variety of realistic patterns of phylogeny and biogeography. Mountaintop extinctions during interglacials and lowland extinctions at glacial maxima favour mid-elevation lineages, especially under the constraints of niche conservatism. According to the results, we suggested that (1) temperature has a profound effect on height and richness of herb communities, while the overstory over is moderating the effect of temperature on herb community structure and influence the abundance of herb community. Conversely, decreases in accumulated temperature weakened the relative importance of overstory cover. We concluded that the interaction of temperature and overstory cover shape the morphology, abundance and richness of herb communities. (2) Our results highlight that herb richness at low elevations is limited by high temperature and therefore drought, and by low temperature at high elevations. We conclude that our results provide trait-based support for the physiological tolerance hypothesis, suggesting that mid-elevation is the most suitable habitat to support a wider range of functional strategies and more species. (3) hump-shape richness pattern also can be shaped by evolutionary process, we found the mountain top species have higher extinaction rate when temperature become warmer, while lowland species have higher extinaction rate when temperature become cooler. Mid-elevation species be favoured because no matter how temperature varied, the species always have suitable habitats. |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/36869]  |
| 专题 | 生态环境研究中心_城市与区域生态国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 蒋子涵. 北京东灵山草本植物多样性海拔格局机制研究[D]. 北京. 中国科学院研究生院. 2015. |
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