Knowledge Resource Center for Ecological Environment in Arid Area
| 绿洲荒漠交错带典型固沙植物水分传输过程研究 | |
| 其他题名 | The hydrological processes of typical sand binding plants in the oasis-desert ecotone |
| 徐世琴 | |
| 出版年 | 2016 |
| 学位类型 | 硕士 |
| 导师 | 吉喜斌 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 水是维持干旱区生态系统及其功能发挥的最关键因子，水分条件决定了植被的生长、分布格局、结构和演替过程。绿洲?荒漠交错带是对水文过程变化响应最为敏感的区域，对于维护绿洲生态系统稳定性具有十分重要的作用。植物水分传输过程涉及多个环节, 包括根系吸水、茎干导水、叶片失水最终将水分散失到大气中，受植物生理生态特征、环境因子等因素的综合影响。本论文利用Li-6400便携式光合作用仪观测了典型固沙植物梭梭、白刺、沙拐枣的气体交换特征，分析了叶片尺度三种植物蒸腾和光合作用，水分利用效率，并引入气孔限制评价模型定量分析了三种植物蒸腾、光合速率的气孔限制。利用Flow32包裹式热平衡茎干液流仪研究了三种植物茎干液流密度的日、生长季动态变化特征，结合气象观测资料分析了茎干液流与环境因子的关系，估算了冠层气孔导度，并构建了两种模型模拟三种植物30分钟时间步长的茎干液流变化。采用全根系挖掘的方法，获得了三种植物根系的分布特征，结合Feddes根系吸水模型定量分析了三种植物的土壤水分来源。研究得出的主要结论如下：（1）三种植物蒸腾和光合速率日变化均呈双峰型，气孔导度在9:00?11:00保持较高水平，之后呈波动下降趋势。梭梭的水分利用效率最大，沙拐枣水分利用效率次之， 白刺最小。梭梭、白刺、沙拐枣蒸腾的气孔限制系数分别为0.71，0.44，0.69，光合的气孔限制系数分别为0.43， 0.64，0.47，气孔对三种植物蒸腾作用的限制明显高于对光合作用的限制。三种植物午间冠层气孔导度随 饱和差（VPD）的增加而降低，呈指数型变化。（2）梭梭茎干液流密度日变化呈双峰型，白刺和沙拐枣茎干液流密度日变化均呈宽幅单峰形。三种植物均存在夜间液流，夜间液流总量分别占生长季总耗水量的12.7 %，2.9 %，10.6 %，由于夜间液流与同期VPD和风速的相关系数很低，据此推测三种植物的夜间液流主要用以水分再分配和茎干补水。生长季，三种植物茎干液流密度存在显著差异：梭梭、沙拐枣茎干液流密度在7月份最大，之后逐渐减弱，而白刺茎干液流密度在7?9月维持较高水平，直到10月中旬才逐渐减弱。（3）光合有效辐射（PAR）、气温和VPD是三种植物茎干液流密度的主要影响因子。茎干液流日变化峰值与PAR、VPD峰值之间存在明显的时滞。另外，茎干液流密度日变化与PAR、VPD存在非对称响应，且非对称的程度存在种间差异。（4）基于茎干液流密度与环境因子响应关系构建模型来模拟梭梭、白刺、沙拐枣30-min时间步长茎干液流密度变化过程。观测值与模拟值的决定系数R2 （P≤0.05）分别为：0.78，0.62，0.75。晴天时的决定系数R2 （P≤0.05）分别为0.86, 0.64, 0,74，降雨发生时白刺基本上观测不到茎干液流，而梭梭与沙拐枣的决定系数R2 （P≤0.05）分别为0.65, 0.71。考虑时滞效应能够显著提升模型模拟精度。但是，模型对低速率茎干液流密度存在低估现象，在未来的研究中需要加以改进。 （5）梭梭为深根系植物，而白刺和沙拐枣为非深根系植物。浅层土壤水（0-40 cm）、中层土壤水（40-100 cm）、深层土壤水（100-300 cm）对熟龄梭梭根系吸水的贡献率分别为26.1 %，32.6 %，33.9 %，对熟龄白刺根系吸水的贡献率分别为23.0 %，60.3 %，16.8 %，对熟龄沙拐枣根系吸水的贡献率分别为70.9 %，24.6 %，4.6 %。熟龄梭梭根系吸收浅层地下水较少，约7.4 %。因此，梭梭主要利用中层及深层土壤水分，还能够利用一定数量的浅层地下水。白刺和沙拐枣主要利用浅层和中层土壤水分。（6）三种植物叶片蒸腾、茎干液流以及根系吸水的动态变化过程以及对环境因子的响应存在显著差异，这是植物适应极端干旱环境的结果。研究还发现，三种植物水分供给与大气蒸腾需求之间的平衡关系还涉及植物的形态适应（如叶面积与根/冠比的调整）。三种植物不同的水分利用策略能够有效的缓解植物对水分的竞争。由于梭梭具有最低的气孔导度、稳定的茎干液流，最深的根系分布，使得该植物比沙拐枣和白刺更加耐旱。上述结论从土壤?植物?大气连续体出发综合阐述了研究区建群植物梭梭、白刺、沙拐枣的叶?气界面、茎干液流以及根?土界面水分传输过程的动态变化特征，揭示了各个界面水分传输的规律，能够为未来深入研究本区生态水文过程、制定科学的植被恢复、水资源管理及生态系统修复措施提供可靠而且详实的数据。由于干旱区呈植物斑块与土壤斑块复合格局，土壤?植被?大气水热传输过程极其复杂，未来仍需要开展大量的研究工作以期获得对本区生态水文过程更丰富的认识。 |
| 英文摘要 | Water is the critical variable for ecosystems in arid regions. It have great effect on the plants growth, distribution, structure, and succession, especially for the oasis - desert ecotone, which is very sensitive to the change of hydrological processes. So, it playing a crucial and unique role in protecting oasis from desertification. The water transport of the plant involves many progresses, and finally transpires into the air through root water uptake, sap flow, and plant transpiration, which was determined by the plant physiological characteristics, environmental variables, and so on.In this study, the gas-exchange parameters of H.ammodendron, C.mongolicum and N.tangutorumin 2014were measured using the Li-6400 portable photosynthetic system to analyze the dynamics of transpiration, photosynthesis, and water use efficiency at the leaf-scale, and to quantify the stomatal control of transpiration and photosynthesis by using two dimensionless index. In order to investigate the water transport in these plants, the danamics of diurnal and sensonal sap flow and its response to environmental variables were studied using Flow32 sap flow gagues based on heat balance method. Two models were developed to simulate 30-min time-scale sap flow. Additionally, the canopy sotomatal conductance to vapor was estimated according to the sap flow data. The root distribution characteristics were analysed by excavating the whole root system of these plants for calculating contribution of different soil layer water to plant transpiration using the Feddes’s water-uptake model. The results indicated that:（1）The daily courses of stomatal conductance of the three species, which all decreased in combination with periodic fluctuation after 11:00 pm, appeared did not follow their diurnal courses of transpiration and photosynthesis. Average stomatal limitation of transpiration （1-Ω） for H.ammodendron, N.tangutorum, and C.mongolicum was 0.71，0.44，0.69, respectively; average stomatal limitation of photosynthesis （Ls） for H.ammodendron, N.tangutorum and C.mongolicum was 0.71，0.44，0.69, respectively. The water use efficiency of these plants was mainly affected by 1-Ω rather than Ls. The mid-day canopy stomatal conductance was decreased exponentially with the increase of saturate vapor pressure deficit （VPD）.（2）The diurnal dynamic of sap flow density for H.ammodendron showed a bimodal change, while the N.tangutorum and C.mongolicum showed a broad unimodal change. The night time sap flow density was significant for these plants. It could explain 12.7 %，2.9 % , and 10.6 % variation of total water consumption for H.ammodendron, N.tangutorum, and C.mongolicum, respectively. Because the VPD and wind velocity imposed weak effects on nighttime sap flow density, so, I presumed that the nighttime sap flow was mainly used for water redistribution and refilling plant xylem. I also found significant difference of sensonal sap flow density among there species （p<0.05）. Additionally, H.ammodendron and C.mongolicum maintained high sap flow density in July, then decreased, while N.tangutorum maintained high sap flow density in August.（3）The sap flow densities of the three species were mainly effected by photosynthetic active radiation （PAR）, air temperature, and VPD. The time lags between the maximum sap flow and the maximum PAR and VPD in a day, and hysteresis between diurnal sap flow and environmental variables were found.（4）Two models, developed based on the relationship between sap flow density and environmental variables, had good performance on simulating the 30 min time-scale sap flow density for these species （the coefficients of determination were 0.78, 0.62, and 0.75 for H.ammodendron, N.tangutorum, and C.mongolicum, respectively）. In sunny days, the model could explain 86 %，64 % , and 74 % variation of sap flow density, respectively. While in rainy days, the model could explain 65 %，71 % variation for H.ammodendron and C.mongolicum, respectively. Sap flow density in N.tangutorum was close to zero. The performance of simulation was significantly improved when the time-lag effects been considered. However, these models underestimated the sap flow density in rainy days and night time, which need to be improved in the future.（5）The root functional type of the three species can be debided into two catergoryies, the phreatophyte and the non-phreatophyte. The result indicated that H.ammodendron belonged to phreatophyte, while N.tangutorum and C.mongolicum were non-phreatophytic species. The H.ammodendron mainly utilized middle and deep soil water and a few groundwater, the N.tangutorum and C.mongolicum mainly utilized shallow and middle soil water, respectively.（6）The dynamics of leaf-scale transpiration, sap flow density, and root water uptake and their responses to environmental variables for thes species were significantly different, which is the result of climate adaption. I also found that the specific morphological adjustments （i.e. leaf area index adaption and the high root/shoot ratio） played very important role in the water balance between water supply and atmospheric evaporative demand for these species. The three species had distinct water use patterns during summer, which could alleviate water competition during long-term water shortage. Low stomatal conductance, stable transpiration rates, and multiple water sources supply of H.ammodendron indicated that this species was more drought-tolerant in the water-limited environment than N.tangutorum and C.mongolicum.These results illustrated the dynamics and mechnisms of water transport in H.ammodendron, N.tangutorum and C.mongolicum, three dominant desert shrubs. It will provide rich and scientific data for deep understanding of the ecohydrological prosesses, and afforestation and water resources managemen in oasis-desert ecotone. However, the interactions among soil, plant, and atmosphere in this area are extremely complicated. So, more researches need to be done in the future for receiving rich information about the ecohydrological processes in arid region. |
| 中文关键词 | 蒸腾 ; 茎干液流 ; 根系吸水 ; 荒漠灌木 ; 干旱区 |
| 英文关键词 | transpiration，stem sap flow root water uptake desert shrubs arid region |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 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/2XILL650/287680 |
| 推荐引用方式 GB/T 7714 | 徐世琴. 绿洲荒漠交错带典型固沙植物水分传输过程研究[D]. 中国科学院大学,2016. |
| 条目包含的文件 | 条目无相关文件。 | |||||
| 个性服务 |
| 推荐该条目 |
| 保存到收藏夹 |
| 导出为Endnote文件 |
| 谷歌学术 |
| 谷歌学术中相似的文章 |
| [徐世琴]的文章 |
| 百度学术 |
| 百度学术中相似的文章 |
| [徐世琴]的文章 |
| 必应学术 |
| 必应学术中相似的文章 |
| [徐世琴]的文章 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
