【作者】 赵阳；

【导师】 赵传燕；

【作者基本信息】 兰州大学 ， 农业生态， 2012， 博士

【摘要】 全球水资源极度短缺和严重分布不均已经成为公认的事实。由于水资源的不均分布,加之地理等因素的制约,全世界出现了面积约3000多万平方公里的干旱区,约占全球陆地总面积的20%。有关研究表明,在我国干旱区的面积(不包括半干旱地区面积)约占全中国陆地总面积的1/4。我国干旱区较为独特,位于中国的西北部,深居内陆,与非洲,西亚,澳大利亚等地的干旱区不同的是,境内又有一系列的高山环绕,海洋湿润水汽很难到达这里,因此气候十分干旱。在干旱区的平原地区植被非常稀少,基本上属于荒漠植物,植物的覆盖度在10%以下,只有在河流两岸以及地下水适宜带才有较多的植物生长,覆盖度才可达到20-40%,但是植被种类有限。植物与水分的关系一直是干旱区生态学研究的中心内容,而受制于水分的植物生长状态及其形态、生理研究又是该领域的热点和难点,成为干旱区生态环境保护和恢复重建中必须面对的基础科学问题。黑河是我国西北地区典型的内陆河流,即黑河流域上游为森林草地,中游为绿洲农田,下游为荒漠绿洲。黑河起源于青海省的祁连山脉,中间流经甘肃省的河西走廊,最后到达内蒙古自治区的额济纳旗,全长总共821km。黑河下游属于典型的干旱区,虽然在这里植物种类很少,植物的生长状态和形态学、生理学特征严重依赖于地下水的分布和埋深,但是却生长着世界上为数不多的荒漠河岸植物—胡杨(Populus euphratica Oliv.)。作为我国第二大荒漠河岸胡杨林,由于水资源的匮乏和人类活动的影响,致使胡杨林面积极度萎缩,现分布面积为2.94x104 hm2,与30年前相比,减少了2.06 x104 hm2。目前胡杨林病、虫害严重,长势不良,天然更新能力极弱,面临着该物种在本地区消失的危险。由于胡杨是维持荒漠河岸林生态系统平衡的关键物种,也是联合国粮农组织(FAO)确定为最急需优先保护的林木基因资源,所以胡杨的保护与重建势在必行。目前,国家也已经将内蒙古额济纳胡杨林规划为国家级保护森林,主要以胡杨等植物群落和生物多样性为保护对象,胡杨的情况才有所好转。然而,依据限制性环境因子(地下水),如何有效的判别胡杨的生长状态,如何合理的进行胡杨的恢复和重建,如何科学的预测未来胡杨的变迁却知之甚少。因此,本论文以额济纳旗天然胡杨林为研究对象,分别在不同的地下水位,分析了胡杨的生长状态和胡杨叶的形态学和生理学特征,希望能为制定胡杨林的保护和恢复重建中提供科学依据。本研究所取得的主要结论如下：1.在不同的地下水位,受水分胁迫程度的不同,天然胡杨的生长状态有较大的差异。胡杨的种群密度(population density),枯枝占所有枝条的比例(ratio of died branches to full branches),树冠,树高均随地下水位的变化而变化。通过研究,可将胡杨的生长状态分为3个级别：(1)地下水位深度在～3m之内时,胡杨长势很好,种群密度最大(-700-～200株/平方公里),枯枝占所有枝条的比例很小(<～10%)。是胡杨生长发育的最佳地下水位。(2)地下水位深度在～3m-～5m之间时,胡杨长势良好,种群密度有所下降(-200--50株/平方公里),枯枝占所有枝条的比例提高(-10%-～60%)。此时,已经发生水分胁迫,是胡杨生长发育较为适宜的地下水位。(3)地下水位深度超过～5m时,胡杨长势差,有的甚至死亡,种群密度最低(<-50株/平方公里),枯枝占所有枝条的比例最高(-60%--100%)。水分胁迫逐渐加剧,是胡杨生长与发育的不适宜水位。2.在不同的地下水位,胡杨叶片形态学、生理学参数均明显发生改变。本研究的三个胡杨叶片形态学、生理学参数为：气孔密度(stomatal density),比叶面积(specific leaf area),稳定碳同位素组成(stable carbon isotopic composition)。三者都可以指示不同的地下水位,也就是不同的水分胁迫程度,且指示程度各有不同。3.胡杨叶气孔密度(stomatal density, SD)可以对不同地下水位做出响应。随着地下水位的降低(水分胁迫程度的加剧)胡杨叶气孔密度呈现先减小后增加再减小的三次多项式模型变化。这个变化趋势是由盐分胁迫和水分胁迫共同作用形成的。即,盐分胁迫发生在较浅的地下水位(～2.0m-～2.7m),水分胁迫发生在较深的地下水位(～2.7m--8.5m),而地下水位在～2.7m附近处很狭小的范围内胡杨可能不受胁迫(不受盐分胁迫和不受水分胁迫)。在水分胁迫的过程中,随着地下水位埋深(水分胁迫程度的加剧),气孔密度形成了三个部分：由于叶面积减小造成的气孔密度增加部分(地下水位～2.7m-～3.7m),由于气孔数量减小形成的气孔密度减小部分(地下水位～5.2m--8.5m)和两者之间的过渡性区域(地下水位～3.7m-～5.2m)。4.胡杨叶片比叶面积(SLA)可以指示水分胁迫。随着地下水位的加深,胡杨的比叶面积以指数方式逐渐减小。地下水位较浅(-2m-～3m)时,比叶面积对地下水位的变化更为敏感。5.胡杨叶片稳定碳同位素组成(d13C)也可以指示水分胁迫。随着地下水位的加深,胡杨叶片d13C值逐渐增加。地下水位在～7m出现阈值,当地下水位深于～7m时,d13C对地下水位的变化更加敏感。6.在气孔密度的制备和计算中,本研究继承了传统的透明胶带粘取法和显微拍照法并具新意的运用了遥感图像处理技术—面向对象分类,进行胡杨叶气孔密度的计算。利用专业的面向对象分类软件(eCognition)对气孔图像进行多尺度分割,然后将生成的分类图像导入ArcGIS软件中计算气孔密度,最后用R语言编写代码进行批处理。利用宏观图像处理技术解决微观的问题,并且取得了处理速度快,计算精度高的效果。更多还原

【Abstract】 It has become a well-known fact that the global water resource is in extreme shortage and with severely uneven distribution. Due to the uneven distribution of water resources as well as the constraint of geographic factors, there appears an arid region of more than 30 million square kilometers all around the world. It approximately occupies 20% of the total global land area. Studies have shown that the area of arid regions in China (not including the area of semi-arid regions) largely occupies about 25% of the total land area. The arid regions in our country are relatively unique for they are largely located at the inner continent or northwestern part of China. Comparing with the arid regions in Africa, western Asia and Australia, these regions in our country are mostly surrounded by huge mountain chains. Therefore, it is very difficult for the wet vapor from sea to reach and correspondingly the climate is rather dry. Vegetation is rare in the arid plains and there essentially grows a kind of desert plant. Plant coverage is below 10% and it can reach 20% to 40% only on the sides of rivers and groundwater-suitable regions, where can grow lots of plant. But the vegetation species is limited. The relationship between plant and moisture is always a research focus in the ecological study of arid regions. Moreover, research for the growing status and morphology as well as physiology of plant, which are all subject to water, is a hot and difficult study issue in this field. This is also a basic must-face problem for the protection and reconstruction of the ecological environment in arid regions.Heihe is a typical inland river in the northwestern part of our country, the upper reaches of which is covered with forest grass, the middle reaches and lower reaches are respectively scattered by oasis farmland and oasis desert. Heihe River originates in Qilian Mountains in Qinghai Province and flows through Hexi Corridor of Gansu Province; it finally reaches the Inner Mongolia Autonomous Region Ejina, with the total length being of 821km. The lower reaches of Heihe River are a typical arid area. Although the plant species is limited here and the growing status, morphology as well as physiological characteristics of the plant extremely depend on the distribution and depth of groundwater, there still grows a globally rare desert plant-Populus euphratica Oliv. As the second largest desert riparian Populus euphratica Oliv forest, its area has withered extremely due to shortage of water resource and the influence of human activity. Now its distribution area is of 2.94 x104 hm2, which has decreased 2.06×10 4 hm2 comparing with 30 years ago. Now the Populus euphratica Oliv forest is heavily damaged by pests and diseases, the growing status of this tree is bad and its natural regeneration ability is very weak. Thus Populus euphratica Oliv faces the danger of disappearing from the region. Because Populus euphratica Oliv is a key species in maintaining the ecological balance of desert riparian forests and it is determined by FAO as the forest genetic resource needing to be protected prior to others, the protection and reconstruction of Populus euphratica Oliv is imperative. At present, our country has already taken the Ejina Populus euphratica Oliv forest as a national protection forest, which is mainly for the protection of Populus euphratica Oliv, plant communities and biodiversity. Then the status of Populus euphratica Oliv has improved. However, according to the restrictive environmental factor (groundwater), we still know little about how to effectively distinguish the growing status of Populus euphratica Oliv, how to make reasonable rehabilitation and reconstruction as well as how to scientifically predict the changes of Populus euphratica Oliv in the future. Therefore, this article took natural Populus euphratica Oliv of Ejina as its study object and analyzed the growing status, the morphology of leaves as well as the physiological characteristics of Populus euphratica Oliv in different groundwater levels. We hope that our study can provide a scientific basis for the protection and reconstruction of Populus euphratica Oliv. The main conclusions of this study are as follows:1. As to different groundwater levels with different degrees of water stress, the growing status of natural Populus euphratica Oliv are quite different. The population density (PD), ratio of died branches to full branches (RBF), the crown and height of Populus euphratica Oliv all vary as the groundwater changes. Generally speaking, the growing status of Populus euphratica Oliv can be divided into 3 levels:(1) population density (-700-～200tree/hm2) is rather high where the groundwater table is less than～3 m, and ratio of died branches to full branches is very low (<～10%). This groundwater level forms the optimum wet conditions for for Populus euphratica Oliv to grow and develop. (2) the density(～200-～50 tree/hm2) is much reduced where the groundwater table is between～3 and～5 m, and ratio of died branches to full branches is promoted (～10%-～60%). At this time, water stress is happened and this groundwater table is appropriate to growth and development of Populus euphratica Oliv. (2) the density(<～50 tree/hm2) is very low when the groundwater table is beyond～5 m, and ratio of died branches to full branches is very high (-60% -～100%). This groundwater table is not suitable for the growth and development of Populus euphratica Oliv.2. The morphological and physiological parameters of Populus euphratica Oliv were significantly changed with different groundwater tables. In this study, three leaf-related morphological and physiological parameters of Populus euphratica Oliv are stomatal density, specific leaf area and stable carbon isotopic composition. Both of them can indicate different different groundwater tables.3. Variation of stomatal density (SD) of Populus euphratica Oliv can indicate different groundwater tables. salt stress dictates leaf stomatal density (SD) of shallow groundwater conditions (less than～2.7 m) and that water stress dictates leaf stomatal density (SD) of deep groundwater conditions (larger than～2.7 m), the narrow zone around～2.7 m probably being a stress-free zone (neither salt stress nor water stress). Within the water-stressed portion (from～2.7 to～8.5 m) or the bell-shaped portion, SD climbing segment (～2.7 -～3.7 m) is leaf-area controlled and the declining segment (～5.2 -～8.5 m) is stomatal-number controlled with the plateau segment (～3.7 -～5.2 m) being the transition.4. Variation of specific leaf area (SLA) of Populus euphratica Oliv can indicate different groundwater tables (water stress). Specific leaf area (SLA) decreases exponentially with increasing groundwater tables. Our research show that specific leaf area (SLA) is more sensitive to groundwater tables when the table is shallow and～3 m of groundwater table seems to be a threshold where SLA becomes less sensitive to groundwater table. 5. Variation of stable carbon isotopic composition (d13C) of Populus euphratica Oliv can also indicate different groundwater tables (water stress). The d13 is also strongly dependent on groundwater table. Our research show that stable carbon isotopic composition (d13C) becomes more sensitive when the groundwater table is deep and-7 m of DG seems to be a threshold where the d13C signature becomes more sensitive to DG.6. In the preparation and calculation of stomatal density, this study has inherited the traditional ways of adhesive cellophane tape emulated and microscopic photographed method, it also made the creative use of remote sensing image processing technology (object-oriented classification) to calculate the Populus euphratica Oliv leaves stomatal density. We used the professional object-oriented classification software (eCognition) to give a multiscale segmentation for the stomatal images. Then we imported the generated classification images into the ArcGIS software to calculate stomatal density. Finally, we made a batch program using R language to deal with a lot of photos’data. Using macro-image processing technology to solve micro-problems, and achieve the effect of fast processing speed, high precision calculation.更多还原