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题名: 河流水文变化对河岸带植物群落的影响
作者: 修晨
学位类别: 博士
答辩日期: 2015-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 欧阳志云
关键词: 草本植物,河流断流,群落结构,洪泛平原,易北河,Grass, Flow cut-off, Community structure, Floodplain, the Elbe River
其他题名: Effects of hydrologic changes to riparian plant communities in rivers
学位专业: 生态学
中文摘要:       由于人为或自然干扰的影响,河流水文条件的变化对河岸带植物群落有严重干扰,植物群落特征发生重大改变。开展河岸带植物群落对水文变化的响应的研究,对维护湿地生态平衡、保护河岸带生物多样性、改善生境质量、提升河岸带管理、促进生态修复及河道可持续发展具有重要的意义。
    本研究以“河流水文变化对河岸带植物群落的影响”为主题,以两个科学问题为主线,从河岸带植物群落对河流水文变化响应的思路出发,在两个案例区(北京永定河和的德国易北河中部) 研究河流水文变化对河岸带植物群落的影响。通过比较不同水文类型样方的植物群落特征的差异,旨在揭示植物群落结构和功能对水文变化的响应。从生物多样性、物种来源、区系结构、生活型、生态型结构和生物量等多方面对不同水文类型生境的植物群落特征进行了详细分析与比较,对受河流断流和洪水等影响、与水文变化相关的环境影响因素进行总结和排序,并探讨这些影响因子对植物群落的影响,最后综合各项结果对河岸带生态系统的管理和生态恢复提出建议。主要结论如下:
    (1) 永定河河岸带草本植物群落共有维管束植物17 科43 属56 种,其中种子植物16 科43 属55 种,蕨类植物有1 科1 种。常年有水河段的种子植物有32种,占总种数的57.1%;季节性有水河段共有22 种,占总种数的39.3%;常年干涸河段有17 种,占总种数的30.4%。在三种水文类型的河段中,种数最多的科均为禾本科和菊科,分别占各自河段总种数的比例在25%以上。与常年有水和常年干涸河段相比,季节性有水河段具有最高的物种丰富度和生物多样性指数。常年有水与季节性有水河段的湿生种构成有最高的相似性。
    (2) 永定河河岸带植物群落的生态型和生活型结构在不同水文河段具有显著性差异,但是它们对河流水文变化具有不同的生态响应。从常年有水到季节性有水河段,一年生和二年生植物比例增加至59%,而多年生植物比例则降低至41%。而随着干旱进一步加剧,到常年干涸河段,生活型结构则基本保持不变。而生态型结构从常年有水到季节性有水河段仅有微小变化,但随着水文条件进一步丧失,到常年干涸河段,生态型结构发生剧烈变化。中生和旱生种的植物比例分别增加了12.8%和11.8%,而湿生种比例则大幅下降了24.6%。常年有水河段的植物地上生物量显著地高于其它两个水文类型河段。
    (3) 北京永定河河岸带植物群落特征的主要梯度与水文因子及相关联的土壤因子有显著的相关关系。RDA 分析结果显示,河岸带水文因子土壤湿度与土壤全氮呈现正相关关系,这表明具有更高营养水平和更湿润土壤的河岸带生境可产生更高的区域性草本生物多样性。河岸带多年生植物更倾向于选择一个具有高土壤养分和常年有水的环境。植物生态型结构与水文因子强相关关系,表明植物群落对于水文条件的长期生态响应。而生物量和土壤全氮、水文因子具有正相关关系,表明河岸带植物在湿润与土壤营养丰富的环境中具有更好的生态功能。
    (4) 德国易北河中部的河岸带草本植物群落共有维管束植物29 科76 属113种,其中种子植物28 科75 属112 种,蕨类植物有1 科1 种。湿润草地的种子植物有35 种,占总种数的30.7%;中湿草地的种子植物共有50 种,占总种数的43.9%;干旱草地有最多的种子植物,共有78 种,占总种数的69.3%。在三种水文类型的分层草地中,种数最多的科均为禾本科和菊科,分别占各自河段总种数的比例在28%以上。三个水文类型分层中,湿润草地的物种丰富度和生物多样性指数最低,中湿草地与干旱草地的香浓多样性指数都较高。中湿草地和干旱草地在各个生态型物种构成上都具有最高相似性。
    (5) 德国易北河中部河岸带植物群落的生态型和生活型结构在不同水文河段具有显著性差异,但是它们对河流水文变化具有不同的生态响应。在三种水文类型分层样方中,多年生植物的比例都占据主导优势地位,比例始终在66%以上。而从湿润草地到中湿草地,一年生植物比例仅有微小的变化;但随着水分进一步递减,一年生植物比例则发生剧烈变化,锐减至干旱草地的13.8%,降幅超过50%。从湿润草地到中湿草地,湿生种从湿润草地的68.6%降至中湿草地的50%,而中生种和旱生种的比例则不断增加。随着水分条件进一步递减,到干旱草地湿生种比例已锐减至30%,而中生种和旱生种比例已经分别增加至45%和25%。
    (6) 德国易北河中部的河岸带植物群落特征的主要梯度与水文因子及相关联的土壤因子有显著的相关关系。RDA 分析结果显示,德国易北河中部的河流水文因子是影响河岸带植物群落结构最重要的环境因子,同时也揭示了与水文因子相关的土壤营养因子对河岸带植物群落也产生影响。河岸带水文因子洪水滞留时间、地下水最大值与土壤有效钾呈现正相关关系,这显示了河岸带水文状况的改变影响了土壤环境因子。本研究结果表明,受洪水物理胁迫较小的河岸带生境可能产生更高的区域生物多样性,河岸带多年生植物倾向于选择具有受洪水干扰较小,但仍有一定水分支持的环境生长。
     (7) 在河流极端水文事件(河流断流和洪水)的影响下,两条河流的植物群落生态型结构和生活型结构对水文变化的响应表现出相同的规律。随着环境中水分条件的增加,从干旱草地到湿润草地、从常年干涸到常年有水河段,湿生种比例增加,中生和旱生种比例减少;一年生植物的比例呈单峰型变化,在“中等干扰”的水文条件生境中(季节性有水和中湿草地)比例最高。两条河流河岸带植物的生物多样性对干扰强度的响应上呈现出相同的规律:随着胁迫干扰(干旱和水淹胁迫)强度的增加,两条河流河岸带植物的生物多样性均逐渐降低。两条河流的河岸带植物群落与环境因子都呈显著相关关系,河流水文因子是影响植物群落的最重要的环境因子,受水文变化影响的土壤因子也对植物群落产生影响。
    对北京永定河和德国易北河中部河岸带植物的研究结果表明,河流水文条件变化对河岸带植物群落结构和功能有很大的影响。河岸带植物群落在生物多样性、生态型结构、生活型结构和生物量等方面对水文变化产生了生态型响应。河岸带植物群落结构和功能的变化与河流水文条件有重大关系,因此河流极端水文事件对河岸带生态系统的影响已不容忽视。
英文摘要:       Riparian zones are highly modified by frequent and intense natural or human-mediated disturbances in most parts of the world, which has caused dramatic changes to riparian plant communities. Studies on the responses of riparian plant community to hydrologic modifications would greatly enhance our ability to maintain ecological balance, preserve ecological diversity, improve management and environmental quality in riparian zone and ultimately develop ecological sustainability and provide scientific basis for future stream ecological restoration.
       In this study, we focus on “the effects of hydrologic modifications to riparian plant communities in rivers” as the main theme, use two scientific questions as the main line. Using the ”space-for-time substitution” method, we investigated the effects of hydrologic modifications to the riparian plant community in Yongding River of northern China and the Middle Elbe River in Germany, by comparing community structure metrics (diversity, plant moisture affinity group, and lifespan) and a function metric (biomass) under three hydrologic plot types. The objectives of this study are (1) to investigate the effects of stream flow cut-off on the riparian plant community by comparing community structure metrics in three streamflows (perennial, seasonal and dried-up); (2) to investigate the effects of flood disturbance on the riparian plant community by comparing community structure metrics in three hydrologic strata grasslands (humid, intermediate, dry). The implications for the management of riparian zone and ecological restoration were also discussed. The main conclusions are as followed:
      (1) A total of 56 herb plant species from 43 genera and 17 families were recorded, including 55 seed plants and 1 fern plant. There are 32 species in perennial flow, accounting for 57.1% of the total; 22 species in seasonal flow, accounting for 39.3% of the total; 17 species in seasonal flow, accounting for 30.4% of the total. The largest families were Compositae and Gramineae, which accounts for more than 25% in each stream section. The stream section with seasonal flow had the highest plant alpha diversity (richness and Shannon index). Hydric species had the largest similarity index between perennial and seasonal flow sites.
      (2) Along the hydrologic gradients in Yongding River, responses of plant moisture group and lifespan were inconsistent within various hydrologic stages,although they changed significantly (chi-squared = 40.59, df = 4, P = 0.001; chi-squared = 18.69, df = 4, P = 0.001 respectively). From perennial to seasonal streamflow, annuals and biennials greatly increased (by ~59 %), whereas perennials decreased by ~41%. The plant moisture group changed only slightly. However, from seasonal to dried-up flow, the percentage of mesics and xerics increased by 12.8% and 11.8%, respectively, whereas hydrics decreased dramatically, by 24.6%. Lifespan remained nearly constant as the drought deepened. Perennial flow sites had significantly higher AG-biomass (P < 0.05) than the other two hydrologic conditions.
      (3) The main gradients of the riparian plant community metrics for the Yongding River were significantly related to the hydrological and related soil variables. The four environmental variables that significantly explained variance in community metrics were FP (F = 4.87, P = 0.012, variance explained = 13%), Moist (F = 3.41, P = 0.024, var. exp. = 8%), TC (F = 4.99, P = 0.008, var. exp. = 11%), and TN (F = 3.86, P = 0.032, var. exp. = 7%). The RDA results showed that the factor Moist was positively correlated with TN, indicating that hydrologic conditions affect soil variables. It suggests that a stream landscape with higher nutrient levels and moister soil produces the greatest regional herb species diversity.
      (4) A total of 113 herb plant species from 76 genera and 29 families were recorded, including 112 seed plants and 1 fern plant. There are 35 species in humid grassland, accounting for 30.7% of the total; 50 species in intermediate grassland, accounting for 43.9% of the total; 78 species in dry grassland, accounting for 69.3% of the total. The largest families were Gramineae and Compositae, which accounts for more than 28% in each strata grassland. The hydrologic strata of humid grassland have the lowest plant alpha diversity (richness and Shannon index), while intermediate and dry grassland have higher alpha diversity. The largest similarity index was found in all type of life span intermediate and dry grassland.
      (5) Along the hydrologic gradients in the middle Elbe River, responses of plant moisture group and lifespan were inconsistent within various hydrologic stages, although they changed significantly. Among three hydrologic strata, perennials occupied the dominant position; the percentage was all more than 66% in each strata grassland. From humid to intermediate grassland, annuals changed only slightly; but as the hydrological regime decreased further, percentage of annuals changed dramatically, decreased from 30% in intermediate grassland to 13.8% in dry grassland with a 50% drop. However, along the hydrological gradients, plant moisture group changed greatly. Hydrics decreased continuously from 68.6% in humid grassland to 30% only in dry grassland. In contrast, mesics and xerics increased both by 19.3%.
      (6) The main gradients of the riparian plant community metrics for the middle Elbe River were significantly related to the hydrological and related soil variables. Hydrological variables (FDmean and GDmax) are the most important environmental factor influencing riparian plant community. The three environmental variables that significantly explained variance in community metrics were FDmean (F = 19.90, P = 0.002, variance explained = 25.5%), GDmax (F = 20.41, P = 0.002, var. exp. = 19%) and AK (F = 3.12, P = 0.038, var. exp. = 3%). The RDA results showed that the hydrological variables were negatively correlated with diversity index, indicating that riparian grassland with less flood disturbance may have the greatest regional herb species diversity.
      (7) Under the influence of stream hydrologic extreme events (flow cut-off and flood), the responses of plant moisture group and lifespan in two rivers to the stream hydrologic changes showed the same pattern. With the increasing moisture conditions in the riparian zone (from dried-up to perennial flow, from dry to humid grasslands), hydrics increased dramatically while mesics and xerics decreased. Meanwhile, the percentage of annuals showed a single peak curve change, in which the highest value was found in the plots sufferd moderate hydrologic disturbance (seasonal flow and intermediate grassland). In addition, the responses of plant diversity in two rivers to the disturbance intensity showed the same pattern. With the increasing intensity of disturbance stress (drought and flooding stress), plant alpha diversity of two rivers both decreased. The main gradients of the riparian plant community metrics for the two rivers were significantly related to the environmental variables. The hydrological varilables were the most important factors influencing the plant community, while the hydrological related soil variables also play a role.
      Based on these results, we conclude that hydrologic modification of stream has a large influence on riparian plant community structure and function. Plant communities respond ecologically to such hydrological change by community metrics (diversity, plant moisture affinity group, lifespan, and biomass). Hydrologic changes correlated significantly with change of plant community. Therefore, it is necessary to give more importance to the effect of extreme hydrological events on riparian ecosystem.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34450
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修晨. 河流水文变化对河岸带植物群落的影响[D]. 北京. 中国科学院研究生院. 2015.
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