元谋干热河谷土壤水分胁迫对典型恢复草种的影响机制
文献类型：学位论文
| 作者 | 贺玉晓 |
| 学位类别 | 博士 |
| 答辩日期 | 2013 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 刘刚才 |
| 关键词 | 干热河谷 土壤水分胁迫 生理生态 影响机制 |
| 其他题名 | Effect Mechanism of Soil Water Stress on Resrotation Grasses in Yuanmou Dry-hot Valley |
| 学位专业 | 自然地理学 |
| 中文摘要 | 我国干热河谷区，年均降雨量少、年均温较高而使该区水热矛盾突出，土壤水分严重亏缺，植被恢复极其困难。本研究以元谋干热河谷典型恢复草种：乡土种扭黄茅、外来种百喜草和柱花草3种禾本科植物为研究对象，采用盆栽和称重控制土壤含水量的方法，在无水分胁迫、轻度、中度和重度水分胁迫4种土壤水分处理下，系统研究元谋干热河谷土壤水分胁迫对供试草种的影响机制，通过分析比较不同梯度水分胁迫下供试草外部生长特性、及影响植物生长特性的、内在的水分生理、光合生理及生理生化的变化特征，揭示当地土壤水分胁迫对典型恢复草种的生理生态影响规律。主要研究结论如下： （1）土壤水分胁迫对供试草生长特性的影响 水分胁迫使3种供试草种的绝对株高、冠幅面积及叶面积减小，生长速度减缓，但比叶重和根容量增加，且水分胁迫对草生长特性的影响具有明显的季节差异，干热季节水分胁迫对草的影响大于雨季和干旱季节。供试草种为了应对水分胁迫，其生长具有明显的资源指向性：随着胁迫的加剧，供试草根生物量增加，同时降低地上部分生物量的积累。干旱季节，3种草都以积累根部生物量为主，同时降低地上部分生物量甚至牺牲地上部分（如扭黄茅）来保全根的生存；在干热季节和雨季植物的萌芽和生长旺盛期，3种供试草在保全生命的前提下通过不同的途径发展地上部分生物量的生长以达到开花结籽、延续种群的目的。 （2）土壤水分胁迫对供试草水分生理的影响 水分胁迫下3种供试草叶片总含水量、自由水含量和相对含水量下降，束缚水含量、束缚水/自由水及水分饱和亏增加，干热季节土壤水分胁迫对叶片含水量的影响大于干旱季节和雨季。3种草叶水势均随着土壤水分的降低而降低。相关分析表明，叶水势与温度呈负相关关系，而与湿度呈正相关关系。干热季节，大气温度是影响扭黄茅叶水势变化的第一影响因子，雨季，大气湿度则成为主要影响因子；各季节大气温度是百喜草叶水势的主要影响因子。重度胁迫下供试草叶片保水力最大，且雨季叶片保水力大于干旱和干热季节。干旱和干热季节水分胁迫下，柱花草保水力最大，其次是百喜草；雨季，以扭黄茅的保水力最大，其次是柱花草。 （3）土壤水分胁迫对供试草光合生理的影响 3种典型恢复草种在不同土壤水分下，其光响应曲线即净光合速率随光合有效辐射的变化表现出基本一致的趋势，均是在低强度光合有效辐射时净光合速率迅速增加，达到一定强度的光合有效辐射后，净光合速率增幅渐趋平缓，采用直角双曲线修正模型拟合较好。不同草种光响应曲线的高低呈相似的变化规律，即净光合速率和最大净光合速率在同等光强时的基本表现为无水分胁迫和轻度水分胁迫大于中度、重度水分胁迫。低强度光合有效辐射时，供试草净光合速率的降低为气孔限制因素起主导作用，随着光合有效辐射强度的升高，供试草净光合速率的降低主要由非气孔限制因素起主导作用。 从光饱和点和光补偿点的变化导致的各供试草有效光强范围变化来看，雨季扭黄茅对光的生态适应能力增强，具有较强的生长潜力；百喜草对干热季节高光强的生态适应能力较强；柱花草中度水分胁迫水平对光环境具有较强的适应性。干热季节扭黄茅和百喜草暗呼吸速率较高，表明在干热季节，供试草叶片是通过暗呼吸提供能量来维持代谢活动，提高叶片生理活性，以抵御水分胁迫对其的影响。 土壤水分胁迫使供试草初始荧光增加，最大PSⅡ的光能转换效率和PSⅡ的潜在活性降低，各处理水平以重度胁迫下的变幅最大，且干热季节草叶绿素荧光参数的增加或降低速率高于干旱季节和雨季，表明随着水分胁迫程度的加剧，供试草PSⅡ反应中心受到一定程度的破坏或可逆失活。 （4）土壤水分胁迫使供试草叶片脯氨酸含量产生了累积效应，以重度水平增加幅度较大。扭黄茅和百喜草叶片脯氨酸含量三个季节的变化大小为干热季节>干旱季节>雨季，而柱花草脯氨酸含量的季节变化规律为干旱季节>干热季节>雨季。 （5）植物对土壤水分的适应有一个耐受范围（即生态幅），短时间地靠近耐受范围下限，不会对植物产生很大的影响，反而会对植物的抗旱起到锻炼作用，但长期地停滞在耐受范围的下限，将会对植物产生较大的伤害作用。 （6）模糊隶属函数对3种供试草抗旱性的综合评价表明，在干热季节，3种供试草的抗旱性大小顺序为百喜草>柱花草>扭黄茅，雨季其抗旱性大小顺序为扭黄茅>柱花草>百喜草，表明百喜草和柱花草对干热河谷极端干热气候有较强的适应性，而扭黄茅一旦成功度过极端的干热天气，在干热河谷具有较强的生长潜力。 |
| 英文摘要 | The dry-hot valley is a typical ecological fragile system, which characterized by a dry climate, obvious contradictory between water and heat and sever soil moisture deficit. Water-poor is a main limited factor for vegetation restoration in the Yuanmou Dry-hot valley. Three typical restoration grasses (Heteropogon contortus, Paspalum notatum and Stylosanthes Swartz) were selected to observe their responses of physiology and ecology to different soil water stress levels controlled by potted-seedlings and weighting method. The variation of growth characteristics, water physiological, photosynthetic physiology and physiological and biochemical of three typical restoration grasses were analyzed and compared under water enough supply, light water stress, moderate and severe water stress to reveal the response mechanism of the selected grasses to local dry-climate and soil moisture deficit. The main results were as follows: (1) Impact characteristics of soil water stress on the grasses’ growth features Under soil water stress, the absolute plant height, crown breadth area and leaf area of three grass species reduced while specific leaf weight and root volume increased. The impact of water stress on grasses’ growth characteristics had significant seasonal differences, and the influence of water stress on grasses in dry-hot season was greater than in rainy and arid season. To adapt to water stress, the grasses’ growth had obvious allocation direction: with the aggravation of water stress, the root biomass increased, while decreased the accumulation of above-ground biomass. In arid season, three species gave priority to root biomass accumulation, while reducing aboveground biomass even sacrifice the aerial parts (such as Heteropogon contortus) to preserve the roots survive. During the dry-hot season and rainy season, the period of plant germination and growing, on the premise of preserving life, the three grasses showed different ways to increase aboveground biomass to achieve the purpose of flowering, fruiting, and continuation of species. (2) Impact characteristics of soil water stress on the grasses’ water physiology With the increase of soil water stress, the leaf water content, relative water content and free water content decreased, and the bound water content, bound water/free water and the critical water saturation deficiency increased for all three kinds of grasses. The influence of soil water stress on leaf water content in dry-hot season is stronger than in the dry season and rainy season. The leaf water potential of three kinds of grasses decreased with water stress increasing. The correlation analysis indicated that the leaf water potential had a negative correlation to atmospheric temperature and a positive correlation to atmospheric humidity. In dry-hot season, the atmospheric temperature was the first factor influencing on the leaf water potential of Heteropogon contortus, atmospheric humidity followed. While in rainy reason, the atmospheric humidity was the major impact factor. The atmosphere temperature was the main factors affecting the water potential of Paspalum notatum in each season. Water-holding capacity reached the maximum under the severe water stress, and it was higher in rainy season than in arid and dry-hot season. In arid season and dry-hot season, the water-holding capacity of Stylosanthes guianensis was higher than that of Paspalum notatum and Heteropogon contortus under soil water stress. While in rainy season, the water-hloding capacity of Heteropogon contortus was highest, Stylosanthes guianensis and Heteropogon contortus followed. (3) Impact characteristics of soil water stress on the grasses’ photosynthetic physiology The changes of light response curve showed same trends for the three typical restoration grasses under different soil water stress levels. The net photosynthetic rate (Pn) was sharply increased at low photosynthetically active radiation (PAR), but after PAR reached certain degree the Pn was increased slowly and the curve became flat. Curve fittings by modified rectangular hyperbola model were performed well. For different grasses the high-low changes of light response curves showed a similar regulation with soil moisture reducing, it was Pn at same PAR showed higher under the water enough supply and light soil water stress than under medium soil water stress and severe soil water stress. With low intensity of PAR, stomatal limitation was the main factor of influencing Pn, but with the increasing of PAR, the main reason for impact of intensity changed from stomatal limitation to non-stomatal limitation. According to the changes of valid intensity range resulted from variations of light compensation point and light saturation point, Heteropogon contortus showed considerably strong adaptability to light ecological adaptability in rainy season, which indicated that Heteropogon contortus had a strong growth potential. And Paspalum notatum had strong adaptability to high PAR ecological adaptability in dry-hot season. Stylosanthes guianensis had strong adaptability to light environment under medium soil water stress in arid season. The dark respiration rates (Rd) of Heteropogon contortus and Paspalum notatum under soil water stress in dry-hot season were higher than in rainy and arid season. This indicated that in order to resist the soil water stress, the leaves metabolic activity were maintained by Rd providing energy to enhance physiological activity. Soil water stress induced the increase of the minimal fluorescence (Fo) and a decrease of the maximum quantum yield of photo-systemⅡ (PSⅡ) (Fv/Fm) and potential activity of PSⅡ (Fv/Fo) of the three kinds of grasses. And the amplitude of variation of them reached the maximum under severe soil water stress. The rate of increase or reduce of fluorescence parameter in dry-hot season were higher than in rainy season and arid season. It means that with the increase of drought extent, the degree of photoinhibition increased, i.e., water stress restrained the photochemical activity in PSⅡ and reduced the light part used in photochemical reactions and actual photochemical efficiency, resulting in response center in PSⅡ damaged or reversible inactive. (4) Soil water stress had a cumulative effect on the leaves Proline content and it reached the maximum under severe soil water stress. The leaves Proline content of Heteropogon contortus and Paspalum notatum decreased by order of dry-hot season, arid season and rainy season, while the leave Proline content of Stylosanthes Swartz decreased by order of arid season, dry-hot season and rainy season. (5) There was a tolerance range of soil water stress (i.e., ecological amplitude) for grasses, withstanding short periods of tolerable water stress, not only it would not have an appatent impact on the grasses, but also it could enhance the grasses’ resistence to drought. But for long-term period of this condition, it would produce a big damage on the plants. (6) Fuzzy subordinative Function was used for comprehensive evaluation of grasses drought resistance. The results showed that the three species decreased in the order of Paspalum notatum > Stylosanthes Swartz > Heteropogon contortus in dry-hot season, while decreased in the order of Heteropogon contortus> Stylosanthes Swartz > Paspalum notatum in rainy season, which indicated that Paspalum notatum and Stylosanthes Swartz had strong adaptability to extreme dry-hot climate in dry-hot valley, and Stylosanthes Swartz once successfully survived at the extreme dry-hot weather, it would have strong growth potential in the dry-hot valley. |
| 语种 | 中文 |
| 公开日期 | 2014-07-23 |
| 源URL | [http://ir.imde.ac.cn/handle/131551/7051]  |
| 专题 | 成都山地灾害与环境研究所_山地灾害与地表过程重点实验室 |
| 推荐引用方式 GB/T 7714 | 贺玉晓. 元谋干热河谷土壤水分胁迫对典型恢复草种的影响机制[D]. 北京. 中国科学院研究生院. 2013. |
入库方式： OAI收割
来源：成都山地灾害与环境研究所
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