Knowledge Resource Center for Ecological Environment in Arid Area
| 干旱沙区草本植物的水分利用特征研究 | |
| 其他题名 | The Water Use Characteristics of Herbaceous Species in Arid Desert Areas |
| 朱瑞清 | |
| 出版年 | 2015 |
| 学位类型 | 博士 |
| 导师 | 李新荣 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 摘 要 植被重建是遏制荒漠化进程和防止风沙危害的重要手段。在干旱沙区土壤含水量低，地下水埋深很深，降水通常是唯一的补给水源，植被的恢复与重建在很大程度上取决于土壤水分的植被承载力。植物水分利用特征是植被重建工程中的植物种选择、植被密度控制与空间优化配置、以及探讨水分平衡与植被演替等关键问题的核心。以往的文献报道多以木本沙生植物，如柠条(Caragana korshinskii)，油蒿(Artemisia ordosica)等为研究对象，研究其形态学或生理变化对水分动态的响应。而对群落中不同草本植物的水分利用关系研究还相对较少。在腾格里沙漠南缘沙坡头地区，草本植物盖度在固定沙丘上可以达到17.0±2.2%，接近灌木盖度，而生物量可以达到4.32±3.2kg?100m-2是灌木生物量的一半；在流动沙丘上草本植物的盖度要大于木本植物，是木本植物盖度的1.6倍，生物量是灌木的73%。由此可见，草本植物在干旱沙区生态系统中的地位和其水分利用特征对干旱沙区的生态平衡的影响是至关重要的。 本文主要以腾格里沙漠东南缘沙坡头地区沙漠-绿洲过渡地带的草本植物作为研究对象， 选择5种沙地类型，即：流动沙丘、半流动沙丘、半固定沙丘、固定沙丘和草原化荒漠。应用植被调查方法对不同沙地类型草本植物分布格局、多样性、生活型、生长动态和群落结构进行了观测研究，并以不同类型沙地上的6种优势草本植物为研究对象，研究不同沙地主要草本植物的水分利用特征和生存策略。另外选择了2种优势木本植物种作为参照。此外对不同生境下土壤含水量、土壤水势、土壤肥力和细颗粒含量梯度变化进行观测，利用控制实验定量研究各草本植物自然状况下水分生理特征和在土壤水分梯度下的水分利用特征。通过综合分析探讨了干旱沙区草本植物的生态适应性规律和草本植物的水分利用特征，取得了如下研究结果： 1.能够定居在流动沙丘上的植物属于高耗水量植物，如：沙米(Agriophyllum squarrosum)，其WUE峰值高，且在较低的水分梯度时就能首先达到峰值。相反，定居在固定沙丘和草原化荒漠的优势植物种，如小画眉草(Eragrostis poaeoides)、茵陈蒿(Artemisia capillaries)，属于低耗水量植物，其WUE峰值较低，其蒸腾耗水量曲线具有“平台期”现象，并且WUE峰值出现在相对较高的土壤水分梯度上。相关性分析结果表明，8种供试植物的种盖度与其所在的根际水分梯度下的日均蒸腾量呈显著负相关关系(R2=0.94，p<0.01)，即：种盖度与蒸腾耗水量有很好的线性负相关关系，这反应了植物在种群水平上的水分利用量大小的过渡特征和适应对策。实验表明先锋草本植物种，如：沙米，能够战胜恶劣的流沙环境(风蚀、沙埋、炙热和干旱的沙丘表面)是靠高耗水量(Tr高、日均蒸腾量高)、低盖度(种盖度低)、快速生长(高WUE峰值，并且WUE出现在较干旱条件下，生命周期短)、“早起”“避热、避辐射”等策略，成功在流动沙丘上定居。相反，固定沙丘和荒漠化草原优势植物种采取的是保守的水分利用方式(低蒸腾速率、低WUE峰值、蒸腾耗水量曲线具有“平台期”现象)和较好的土壤生境(土壤养分高，细颗粒含量高和因此形成的对雨水的高截留，相对粗糙的土壤表面和相对较高的植被郁闭程度所形成的低土壤表面温度，低风蚀，低沙埋，低辐射)，以长期适应干旱条件。 2. 固定沙丘和草原化荒漠的优势草本植物种为低耗水量草本植物，根系总体较其他草本植物浅(4-15cm)，主要利用表层土壤水分，受降水影响较大，年生物量和种群盖度波动较大，是干旱沙区生态系统中的机会主义者(opportunist)，如：小画眉草和茵陈蒿。在干旱少雨的年份，它们在草本植物种中发芽率相对最高，死亡率也为最高(分别为：94.15%和46.33%)，不与其他植物争夺水分；在雨水好的年份，其发芽率仍为最高，死亡率相对其他草本植物高，但是比起干旱年份大幅降低，利用7、8、9月份的雨季快速建立生物量，完成生命周期，在其各自所在生境草本植物种中的IV值达到最高(分别为124.1，128.4)，是靠典型的r-策略适应干旱沙区生境。 相反，流动沙丘和半流动沙丘上的优势草本植物种是高耗水量植物，根系总体较其他草本植物深(>40cm)，主要利用流动半流动沙丘深层土壤水分，受雨水影响较小，年生物量和种盖度波动较小，发芽率在草本植物种是最低的，但是成活率是最高的，在其各自所在生境草本植物种中的IV值达到最高，是靠典型的k-策略适应干旱沙区。 3. 本研究发现在自然状况下，干旱沙区各植物蒸腾速率(Tr)日变化所形成的“单峰型” 曲线代表着植物的较强的蒸腾能力和较强的水分利用能力，“双峰型” 曲线代表着植物对干旱沙区土壤水分亏缺的适应和生理调节能力，当土壤水分充足时“双峰型” 曲线植物也可以转变成“单峰型” 曲线。 在蒸腾速率和光合日变化曲线中，“单峰型”或“双峰型”甚至是“多峰型”并不是植物固有的特征性曲线，其线型同时受天气因子、植物自身生理调节、和土壤水分供应量的共同制约。并且，在相同的土壤水分条件和天气状况下，蒸腾速率日变化曲线和光合速率日变化曲线的线型也可以不一致，本研究认为蒸腾速率曲线容易受到土壤含水量的影响，其线型受制于土壤含水量；光合速率日变化曲线更容易受植物自身的生理调节的影响，对天气因子和土壤水分的响应相对较弱。 4. 本文依据土壤水分梯度下植物水分消耗量的变化曲线，把研究区域的8种优势植物种划分为高水分消耗量植物、温和水分消耗量植物、低水分消耗量植物3种水分消耗类型： a. 高耗水量植物，此类植物有：沙米、刺蓬(Salsola ruthenica)、花棒(Hedysarum scoparium)、油蒿。其日均蒸腾耗水量随着土壤水分梯度的增加而增加，在干旱胁迫减小时(土壤含水量>1.7%)蒸腾耗水量大幅度增加(>土壤水分为1.1%时日均耗水量的3.6倍)在接近田间持水量的时候这种增加趋势仍在持续，且日均蒸腾耗水量>12.21±1.09 g?g-1d-1； b. 低耗水量植物，有：小画眉草、茵陈蒿。此类植物日均蒸腾耗水量随土壤水分含量的增加而增加的幅度小(土壤含水量增至1.7%时，日均蒸腾耗水量<1.1%时的1.8倍)，当土壤含水量进一步增加的时候，植物蒸腾耗水量表现出一定的“平台期”效应，最大耗水量小于2.45g?g-1d-1； c. 温和用水植物，有：蒙古虫实和雾冰藜(Bassia dasyphylla)。此类植物日均蒸腾耗水量大小介于高耗水量植物和低耗水量植物之间，耗水量曲线也随着土壤含水量增加而增加，但增加趋势介于高耗水量植物和低耗水量植物之间，没有明显的“平台期”现象，本文定义为温和用水植物。 以上结果解释了本研究区域的各植物具有相对较高的生境专一特征，即：高耗水量植物特定生存在高含水量低养分土壤，如沙米仅生长在流动沙丘上；而低耗水量植物仅生存在低土壤水分和高养分环境，如茵陈蒿多分布在草原化荒漠上。本研究亦表明，最高水分含量沙地承载最少的草本植被(流动沙丘植被稀疏但其上草本植物是属于高耗水量型植物)，而最低水分含量沙地承载最大的草本植被(草原化荒漠植被茂密但其上草本植物属于低耗水量型植物)，这一现象说明草本植物的水分生理特征对其分布和不同类型沙地植被结构有较大影响，同时也说明土壤质地对草本植物的分布具有较大影响，即质地较细的土壤(粘粒和粉粒含量)和土壤肥力(总氮、有机质含量)有利于草本植物的繁衍。 综上所述，草本植物是干旱沙区生态系统重要的组成部分和水分利用主体，其水分利用生理特征的多样性增加了干旱沙区生态系统的稳定性。本研究结果对风沙自然植被重建和恢复以及荒漠草原的生态保护实践具有重要的借鉴意义。 |
| 英文摘要 | ABSTRACT Revegetation is a common method used to curb desertification processes and prevent wind erosion to adjacent areas. But water supply is extremely limited in arid desert area, rainfall is usually the only water supply, water supplies play a restrictive role on revegetation or rehabilitation programs in this area. Plant water use characteristics thus play a key important role in chosing revegetation species, optimizing the revegetation density and the plant species collocation ratio, determining water consumption thresholds of arid desert area, predicting soil water balance and succession orientation issues and so on.Previous studies were around woody psammophytes, such as Caragana korshinskii and Artemisia ordosica, in terms of morphological or physiological changes in individual level or community level perspectively. Comparative studies on adaptive physiological traits between species of different herbs are rare, let alone studies combining physiological characteristics and environmental gradients. In fact, in Shapotou area in the southest fringe of Tenger Desert, the herbaceous cover is up to 17.0 ± 2.2% at fixed dunes, approximate to that of shrubs, and the biomass is up to 4.32 ± 3.2 kg?100m-2, close to half of that in shrubs. At shifting dunes, herbaceous cover is more than that of shrubs, 1.6 times larger as that of shrubs, the biomass is reach 73% of shrubs. Thus the importance of herbaceous species and the influence of herbaceous water use characteristics is vital for the ecosystem stability and equilibrium in arid desert areas. This study focused on an desert-oasis transitional zone on the southeast fringe of Tengger Desert in Shapotou region. According to sand-fixation degree and the vegetation situation, this study selected five different sandy land types as study area: shifting dunes, semi-shifting dunes, semi-fixed dunes, fixed dunes and steppified desert. The herbaceous distribution pattern, vegetation species diversity, life type, growing dynamics and community structure were observed by vegetation survey methods, during which we selected six dominant herbaceous species among different type of sandy lands, to research on the water use characteristics and survial strategies. Two dominant woody plants were choosen as a comparison, representing water use characteristics and survival strategies of woody vegetation.Environment gradients (soil moisture, soil fertility, soil water potential and fine particle content) were accquired by field experiments;absolute quantitative methods were applied to obtain the interspecific plants' physiological and water use characteristics under soil moisture gradients. This study was trying to give a comprehensive understanding on the adaptative ecological features of herbaceous species in arid desert area, and to define and clarify herbaceous water use characteristics. Main results as: 1. The herbaceous plants who can surviv on mobile sand dunes are prodigal water use plants (Agriophyllum squarrosum) with high water consumption, high crest value of WUE and cresting at relatively low moisture gradients. In contrast, the dominant herbaceous plants settled in fixed dunes and steppified deserts are conservative water use plants (Eragrostis poaeoides, Bassia dasyphylla and Artemisia capillaries), with low WUE crest, plateau phenomenon occurring in their diurnal transpiration curve, WUE cresting at relatively high soil moisture gradients. Correlation analysis showed that species cover of eight kinds dominant plants was significantly and negatively correlated with diurnal transpiration under the soil moisture gradient of rhizosphere (R2=0.94, p<0.01)。Namely, herbaceous cover has a good linear correlation with transpiration, which helps to understand that herbaceous distribution pattern and community structure were strongly affected by soil moisture gradients in arid desert area. The results also showed that pioneer herbaceous species plant (Agriophyllum squarrosum) can survive the extreme severe environment (shifting sand surface, with relatively high wind erosion, sand burial, hot and drought of dune surface) is by high water consumption (high Tr and diurnal transpiration volume), and low plant cover (low species cover), and fast growth (high WUE crest, and WUE cresting at relatively low soil moisture conditions, short life cycle). So as to take the full advantage of high soil water content of shifting dunes, maximize the best out of worst, establishe the first green lifeline while there is no any other plants can do. In contrast, herbaceous species living in fixed dunes and steppified deserts (Eragrostis poaeoides and Artemisia capillaries) are conservative water users (with low Tr, relatively low WUE crest, low diurnal water consumption and plateau curve) taking the full advantage of the improved conditions of high fixation soil surface (high soil nutrients, high content of fine particles and thus the high retention of rainwater) and the relative superiority of the micro-environment (relatively rough surfac？e and higher degree of vegetation canopy closure, low surface temperature, low wind erosion, low sand burial, low solar radiation), so as to chronically adapt to drought conditions in high fixation sandy lands. 2. The dominant herbaceous species in fixed dunes and steppified deserts (Eragrostis poaeoides and Artemisia capillaries) are conservative water users, with relatively shallower root system (4-15cm deep) compared with other herbs, mainly depending on top soil surface water, which has a strong reliance on precipitation, and the biomass and species cove fluctuates with precipitation varing. Thus they play a role of opportunist in arid desert ecosystem.In drought years, Eragrostis poaeoides and Artemisia capillaries had a relatively high germination rate, but also highest mortality (respectively: 94.15% and 46.33%), thus there is no vie occurred for water with other plants;In the year with abundant precipitation, they has a high germination rate, and a relatively low mortality (although higher than other herbs but lowest when compared with drought and normal years), making good use of high precipitation season (in July, August, Octomber) establishing biomass rapidly, completing life cycle, achieve the higest IV value (respectively 124.1, 128.4) among herbaceous in their respective type of sandy land. The dominant herbaceous species in fixed dunes and steppified deserts (Eragrostis poaeoides and Artemisia capillaries) rely on typical r-strategy to adapt to arid desert habitats. Whereas, the dominant herbaceous species surive in shifting and semi-shifting dunes (Agriophyllum squarrosum, Salsola ruthenica) are prodigal water use plants, with deep root system (>40cm), relying mainly on the abundance soil water in deep soil layers of shifting and semi-shifting dunes, less influenced by precipitation, the biomass and species cover fluctuated little. They had the lowest germination rate in herbaceous species, but the highest survival rates, and achieved the highest IV values (respectively 274.5,189.4) among herbaceous species in their respective type of sandy land, relying on typical k-strategy adapting to arid desert area. 3. The unimodal curve of diurnal Tr variation of each plant in arid desert area represents the strong transpiration capability and strong water use capability, while bimodal curve represents the adaptability and self-regulation of plants on soil water deficit. This study found that bimodal curve type plants can also be unimodal curve type plants when soil water is sufficient. Thus the curve types (unimodal, bimodal or multimodal) of diurnal Tr and Pr variation do not represent a characteristic curve that links to certain plants, the curve types were determined by the joint restriction of physiological adjustments of plants, water supply and meterological factors. Further more, the curve of Tr and Pr doesn’t match under the same environmental conditions in terms of soil moisture and meterological factors. It is to say，the Tr curve is more affected by soil water content, or restricted by soil water content, while the Pr curve is more affected by physiological adjustments of plants, less by water and meterological conditions. 4. This study classified the 8 dominant herbaceous species in the study area into 3 types of water use characteristics, based on plant diurnal water consumption curves, respectively prodigal water use plants, moderate water use plants and conservative water use plants: a. prodigal water use plants, such as: Agriophyllum squarrosum, Salsola ruthenica, Hedysarum scoparium, Artemisia ordosica. Their average diurnal transpiration consumption increase with soil moisture,with the decreasing of in drought stress (soil moisture 1.7%) the diurnal transpiration consumption increases drastically (3.6 times as that of soil moisture 1.1%), the increasing trend continues when water contents increased closely to field capacity, and the transpiration consumption is higher than 12.21±1.09 g?g-1d-1; b. conservative water use plants: Eragrostis poaeoides, Artemisia capillaries. They had a smaller increasing range with soil water contents increasing (less than 1.8 times as that of soil moisture 1.1% when soil moisture increased to 1.7% ), when soil moisture further increased the transpiration consumption curve showed a plateau effect, the maximum water consumption was less than 2.45g?g-1d-1； c. moderate water use plants: Corispermum mongolicum, Bassia dasyphylla. The transpiration amount of this kind of plants was in the range between prodigal water use plants and conservative water use plants, the water consumption curve increased with the increasing of soil water content, but the increasing trend was between prodigal and conservative water use plants, with no obvious plateau effect was observed. The results can also be a reasonable explanation to the study areas that the plants with relatively high site-restricted distribution, namely: prodigal water use plants restrictedly distributed in sites with high water content and low soil nutrient, such as Agriophyllum squarrosum, specificity grows on shifting dunes; while conservative water use plants restrictedly distributed in sites with low water content and high soil nutrient, such as Artemisia capillaries restrictedly grows on steppified deserts. As well, the results can be reasonable explanation to the phenomenon that a the sites with highest water content carrying the least vegetation (shifting dunes have sparse vegetation but prodigal water use herbs), while the sites with the lowest moisture content carrying the largest amount of vegetation (steppified deserts with dense vegetation but the herbs belong to the conservative water use plants). To sum up, the aboundance of herbaceous water use physiology increases the stability of ecosystems in arid desert areas, and herbaceous species are the main part of water use and an important part consist the arid desert ecosystems. The results of this study provided scientific basis for China's desert control, vegetation restoration and ecological environment construction. |
| 中文关键词 | 干旱沙区 ; 草本植物 ; 水分利用特征 ; 植被重建 ; 环境梯度 |
| 英文关键词 | arid and desert area herb water use characteristics vegetation environmental gradients |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287529 |
| 推荐引用方式 GB/T 7714 | 朱瑞清. 干旱沙区草本植物的水分利用特征研究[D]. 中国科学院大学,2015. |
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