KMS XINJIANG INSTITUTE OF ECOLOGY AND GEOGRAPHY，CAS
| 基于氢氧稳定同位素胡杨(Populus euphratica)和柽柳(Tamarix ramosissima)的水分利用策略研究 | |
| 周天河 | |
| Subtype | 硕士 |
| Thesis Advisor | 赵成义 |
| 2015 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Discipline | 自然地理学 |
| Keyword | 胡杨 柽柳 稳定氢氧同位素 水分利用策略 实生幼苗 根系 |
| Abstract | 胡杨(Populus euphratica)和柽柳(Tamarix ramosissima)是塔里木河流域的两种主要优势物种，对于维护荒漠河岸林的生态平衡，隔断沙漠、保护绿洲农牧业生产有重要作用。近几十年来，人类活动改变了流域的地表水文过程，胡杨和柽柳的生态水文过程发生了巨大变化。研究胡杨和柽柳的水分来源和用水方式，探讨它们的水分利用策略及对干旱环境的适应机制，为揭示干旱区荒漠河岸植物生态水文过程机理，干旱区生态系统的保护和恢复措施提供依据。本文基于氢氧稳定同位素技术，通过控制试验分析了不同地下水埋深下胡杨和柽柳的幼苗茎干水和各潜在水源（土壤水、地下水）的δD和δ18O同位素组成特征；结合植物株高、根系等生长指标测定，利用IsoSource模型和平均深度模型，研究了胡杨和柽柳幼苗对各潜在水源的利用比例和根系吸水的平均土壤深度；通过野外试验测定，分析了塔里木河上游距河岸不同距离胡杨和柽柳茎干水和各潜在水源的δD和δ18O同位素组成特征，量化了胡杨和柽柳对各潜在水源的利用比例。取得的结论如下： （1）单一生境下胡杨和柽柳的幼苗茎干水δ18O值差异不显著，二者具有相似的水分利用特征。在0.3 m和0.8 m地下水埋深下，深层土壤水和地下水是其主要水源，利用比例超过80%；在1.3 m和1.8 m地下水埋深下，浅层土壤水为其主要水源，直接利用地下水的比例很小；在1.8 m埋深时，胡杨幼苗不能直接利用地下水，对0-80 cm土壤水的利用比例高达79.9%，柽柳幼苗利用地下水的比例仅为12.9%，对0-80 cm土壤水的利用比例达到62%。 （2）混合生境下，胡杨和柽柳的幼苗对水分的竞争作用使柽柳幼苗主要利用深层土壤水和地下水，胡杨幼苗主要利用浅层土壤水，柽柳幼苗茎干水δ18O值显著小于胡杨幼苗。地下水埋深为1.3 m时，胡杨幼苗主要利用浅层0-40 cm土壤水，利用比例为46.6%，柽柳幼苗主要利用60-130 cm土壤水和地下水，比例分别达到47.3%和24.5%。柽柳幼苗利用水分的平均深度显著深于胡杨幼苗，表明柽柳幼苗对干旱环境的适应能力优于胡杨幼苗。 （3）胡杨幼苗各级根系的生物量均小于柽柳幼苗。胡杨幼苗根系总量在0.8 m 地下水埋深条件下达到最大，为36.07 g；而柽柳幼苗在该地下水埋深下根系生物量最小，仅为27.29 g，在0.3 m和1.3 m地下水埋深时达到最大，分别为65.87 g和75.05 g。胡杨和柽柳的幼苗的细根垂直分布随着地下水埋深的增加而加深，且地下水埋深越深，细根生物量在深层土壤中所占的比例越大。混合种植情况下胡杨和柽柳的幼苗细根生物量在深层土壤所占比例均大于单一种植情况。胡杨幼苗的耐盐和耐旱能力均弱于柽柳幼苗。 （4）柽柳茎干水的δ18O值小于胡杨，二者均随河岸距离增加而减小。在河岸，胡杨可利用14.2%的河水，柽柳对河水的利用比例最大达到35.3%，二者对0-100 cm土壤水的利用比例较高。远离河岸，胡杨主要利用大于120 cm深的土壤水以及地下水，地下水的利用比例可达40%~50%；柽柳以地下水作为其主要水源，最大利用比例可达94.5%。胡杨生长需要适宜的地下水埋深（3.5-4.2 m），柽柳在浅地下水埋深和大于4.5 m的深地下水埋深条件下均能良好生长，对不同水分条件的适应能力优于胡杨。 |
| Other Abstract | As the dominated species in Tarim River Basin, Populus euphratica and Tamarix ramosissima play an important role in maintaining ecological balance of desert riparian forests, sapcing desert and protect the agricultural in oasis. However, the distribution areas of P. euphratica and T. ramosissima have withered extremely due to hydrological processes change by human in the Tarim River Basin in recent decades. We studied the water uptake of P. euphratica and T. ramosissima, explored the water-use strategy and the adaptive strategy of arid environment under different moisture conditions, which will be important significance to reveal the ecohydrology process of desert riparian forests and to protect and reconstruct the ecological environment in arid regions. A pot experiment with 4 different groundwater depths was conducted. The δD and δ18O compositions of the stem water and potential water sources (soil water and groundwater), and photosynthetic characteristic parameters were measured. By using the IsoSource model and the mean depth of water uptake model, we calculated the contributions of potential water sources to total plant water uptake and the mean soil depth of water uptake by P. euphratica seedlings and T. ramosissima seedlings under different groundwater tables. In the upstream of Tarim River, we also measured the δD and δ18O compositions of the stem water from P. euphratica and T. ramosissima and potential water sources in the riparian zone with different water tables. The results were as follows: The rates of water uptake for P. euphratica seedlings and T. ramosissima seedlings planting alone were not significant, with a similar δ18O value of stem water. When the groundwater tables reached up to 0.3 m and 0.8 m, the soil water was favorable for their growth, that is, P. euphratica seedlings and T. ramosissima seedlings mainly used groundwater and lower soil water, with the utilization rate over 80%. When the groundwater tables were 1.3 m and 1.8 m, soil water stress was heavy, P. euphratica seedlings and T. ramosissima seedlings used shallow soil water primarily. Populus euphratica seedlings could not use groundwater directly when the groundwater table was 1.8 m, and obtained 79.9% of its water from the soil layer 0-80 cm, Tamarix ramosissima seedlings obtained 12.9% and 62% of its water from groundwater and the soil layer 0-80 cm, respectively. When P. euphratica seedlings were coexisted with T. ramosissima seedlings, their water-use strategies were changed to reduce the competition for water. T. ramosissima seedlings was mainly used lower soil water and groundwater, obtained 47.3% and 24.5% of its water from the soil layer 60-130 cm and groundwater respectively when the groundwater was 1.3 m. While P. euphratica seedlings was mainly used shallow soil water from the soil layer 0-40 cm, with the utilization rate over 46.6%. These results suggest that T. ramosissima seedlings were much easy to adapt the drought environment than those of P. euphratica seedlings in the arid region. The root biomass of different orders of P. euphratica seedlings was less than that T. ramosissima seedlings, and the maximum value was 36.07 g when the groundwater table was 0.8 m. While the root biomass of T. ramosissima seedlings in the same groundwater table was the minimum, with a biomass of 27.29 g. When the groundwater tables reached up to 0.3 m and 1.3 m, the root biomass of T. ramosissima seedlings was a maximum, with the biomass of 65.87 g and 75.05 g respectively. The vertical distribution of fine roots of P. euphratica seedlings and T. ramosissima seedlings was deeper as the groundwater depth increased. The deeper the groundwater table was, the greater the proportion of fine root biomass in the deep soil layer accounted. Salt and drought tolerance of P. euphratica seedlings was weaker than that of T. ramosissima seedlings. The δ18O values of stem water decreased as the distance far away from river increased, and the δ18O value of stem water from T. ramosissima was lower than P. euphratica. At the river bank, P. euphratica and T. ramosissima could use stream water directly, the largest utilization rate of P. euphratica was 14.2%, and 35.3% for T. ramosissima. The contribution of shallow soil water to water uptake was high. Far away from the river bank, the contribution of subsoil water in 100-300 cm layers and utiliazation of groundwater increased, and the contribution of shallow soil water decreased. P. euphratica mainly used the soil water under 120 cm layers and also the groundwater, with the largest utilization rate of groundwater 40%~50%. T. ramosissima mainly used groundwater, with the largest rate 94.5%. P. euphratica could survive at suitable water tables (3.5~4.2 m), T. ramosissima could grow well in shallow groundwater area and the area with groundwater table under 4.5 m. Comparition the water sources between P. euphratica and T. ramosissima, the adaptability of T. ramosissima was superior than that P. euphratica under variable water availabilities. |
| Subject Area | 自然地理学 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xjlas.org/handle/365004/14683 |
| Collection | 研究系统_荒漠环境研究室 |
| Affiliation | 中科院新疆生态与地理研究所 |
| Recommended Citation GB/T 7714 | 周天河. 基于氢氧稳定同位素胡杨(Populus euphratica)和柽柳(Tamarix ramosissima)的水分利用策略研究[D]. 北京. 中国科学院大学,2015. |
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