论文标题:干旱区植物的水分选择性利用研究
Studies on Selective Utilization of Water by Plants in Aridland Region
论文作者
论文导师 卢琦；孟平,论文学位 博士,论文专业 水土保持与荒漠化防治
论文单位 中国林业科学研究院,点击次数 495,论文页数 119页File Size6933K
2007-06-01论文网 http://www.lw23.com/lunwen_2692862/
aridland; plant water sources; water-use efficiency, WUE; stable isotopes; ~(13)C; D; ~(18)O
为研究典型荒漠植物对干旱环境的适应策略，探讨极端环境条件下植物与环境的互动关系，本文选择具有代表性的荒漠生态系统：干旱区甘肃民勤绿洲—荒漠生态系统和极干旱区内蒙古额济纳绿洲—荒漠生态系统为研究对象，利用稳定同位素D、~(18)O、~(13)C，结合不同生境内植物的生理生态学特征的测定，对干旱区典型绿洲荒漠植物的水分利用来源和水分利用效率进行研究。主要结论如下： 1、不同典型荒漠植物的水分来源及水分利用效率存在差异 利用稳定同位素D和~(18)O，对不同季节内民勤半固定沙丘梭梭(Haloxylon ammodendron)、白刺(Nitraria tangutorum)、沙拐枣(Calligonum mongolicum)，丘间低地沙蒿(Artemisia arenaria)、披针叶黄华(Thermopsis schischkinii)，灌溉井附近沙枣(Elaeagnus angustifolia)的水分利用来源研究表明，不同植物的稳定同位素值存在显著差异(P＜0.05)；土壤水的D和~(18)O在70cm以上土层有显著分馏；在夏季的干旱月，白刺主要利用浅层土壤水(＜1.5m)，梭梭主要利用较深层土壤水(＞1.5m)，沙拐枣主要利用地下水(深层土壤水)，沙枣主要利用附近灌溉井水渗透补给的较深层土壤水(＞2m)，沙蒿、披针叶黄华利用丘间低地较深层(粘土层)贮存的水分补给的较深层土壤水(＞2m)；在秋季，梭梭、白刺和沙拐枣能够利用较大脉冲降雨补给的土壤水；在春季植物萌动发芽期，梭梭、白刺和沙拐枣都主要利用浅层土壤水维持正常的生命活动。对土壤水的利用深度由深到浅顺序为：沙拐枣、梭梭、白刺。同位素信号表明沙拐枣事实上也是深根性植物，甚至能够达到地下水位的深度；由于在2.0m处遇到的干沙层给土壤的取样带来困难，因此，本研究没有进行深层土壤的取样和研究，如果能够对更深层的土壤进行分析，应该有助于对沙拐枣水分利用的理解。 2、典型荒漠植物对降雨的吸收利用 利用稳定同位素D和~(18)O，研究了干旱区水分的主要来源—降雨对典型绿洲荒漠植物水分利用的影响，结果表明，对强度大的降雨(47.6mm)，不同植物都可以在相对较长的时间内持续吸收利用。但不同植物对降雨的响应不同，沙蒿、沙米(Agriophyllum squarrosum)对降雨的反应较为敏感，降雨当天就可以利用雨水；而梭梭、沙拐枣和白刺则第二天才开始吸收利用。对较小强度的秋季降雨(3-6mm)，典型荒漠植物也可以吸收利用，但是持续时间短。 3、不同生境胡杨(Populus euphratica)的生理生态特性及水分利用研究 利用稳定同位素D、~(18)O和~(13)C，结合光合特征、叶水势等生理生态学指标的测定，对胡杨在干旱环境下的适应策略进行研究，发现：不同生境内胡杨的主要水分来源都是地下水，而地下水主要来自黑河河流的间断补给；胡杨成熟木主要利用地下水，幼苗主要利用来自地下水补充的较深层土壤水；距河岸越远，胡杨的水分利用效率越高。 生态输水一周后，距河岸较近的胡杨成熟木对河水的利用程度显著增加，距河岸较远的林带中间(距河岸110m)和近戈壁处(距河岸250m)胡杨的水分利用来源没有明显改变。生态输水可以促进河岸胡杨林的生长，持续时间较长的生态输水可以促进距河岸较远处(18km)的戈壁上的胡杨林的生长；持续时间较短、水量较少的生态输水仅在短时间内、对距离河岸较近的胡杨生长有用，对距离河岸较远的胡杨林没有显著作用。这可以为黑河生态输水的方式提供借鉴。 4、荒漠植物的水分利用效率及水势、光合速率的研究 利用稳定同位素~(13)C研究了典型荒漠植物的长期水分利用效率，并测定了植物的水势指标。研究结果显示，植物叶片的碳同位素组成具有相同的变化趋势，在干旱的7月较高(WUE高)，降雨量多的8月、9月降低(WUE)。民勤荒漠植物水势由高到低的时间依次为：8月、9月、7月，与水分利用效率的季节变化反应的适应特征有相同趋势。 由于沙拐枣主要利用地下水(或深层土壤水)，且蒸腾速率高，水分利用效率低于梭梭，因此在荒漠生态系统植被恢复过程中，大量栽植这类利用深层水源的植物，会与梭梭人工林竞争水分，影响退化梭梭人工林植被恢复；甚至可能会消耗更多地下水，不利于区域地下水位的保持。尤其对于额济纳绿洲来说，地下水是胡杨赖以生存的基础，因此在选择造林树种时，对利用深层水源的植物种选择需要慎重考虑。
To examine the adaptive strategies of representative desert oasis plants developed underwater stress and to interpret the relationship between plants and environment in both arid andextreme arid area in China, stable isotopes of hydrogen (D), oxygen (~(18)O), and carbon(~(13)C)were used to infer possible water utilization patterns and water utilization efficiency(WUE) of several dominant species in Minqin arid oasis-desert ecosystem, GanSu, China andEjin extremely arid oasis-desert ecosystem, Inner Mongolia, China. The main result of thisstudy are summerized as follows. A. Variation in water utility pattern and WUE among desert plant species: TheδD andδ~(18)O values for stems water, soil water, and groundwater were compared toidentify water sources for the small arbor Haloxylon ammodendron, the shrub Nitrariatangutorum and Calligonum mongolicum in semi-fixed sand dune, the subshrub Artemisiaarenaria and the perennial grass Thermopsis schischkinii in lowland between sand dunes, andthe shrub Elaeagnus angustifolia near an irrigation well. The stable isotope ratios of xylemwater were significantly different among species (P＜0.05). Strong isotopic enrichment ofhydrogen and oxygen occurred in soil layer shallower than 70 cm. In the dry month of summer,N. tangutorum used shallow soil water (＜1.5 m), H. ammodendron used water in deeper soillayer (＞1.5 m), while C. mongolicum mainly relied on groundwater (or deep layer soil water).E. angustifolia used water in soil layer deeper than 2m, which was recharged mainly by theirrigation water. A. arenaria, T. schischkinii and E.angustifolia used water at seem deep soillayer which was recharged by water stored in wet sand layer or claypan. In autumn, soil waterrecharged by large precipitation was the main water source for three species in semi-fixed sanddune, whereas the growth of these species in spring benefited effectively from water in uppersoil layer. The sequence of depth of soil water layer supporting three dominant species was listfrom deep to shallow as: C. mongolicum. H. ammodendron, N. tangutorum. The utility of groundwater by C. mongolicum based on isotope signal implies that its rootsystem is long enough to uptake groundwater. Nevertheless, soil in deeper layer was notsampled in our study because it was difficult to break through dry sand layer at about 2.0 mdepth. B. Utilization of summer rains by dominant desert plants: The relationship between the size of summer rains and water utilization of desert plantswas evaluated by comparing stable isotope ratios of different waters. The stable isotope data showed that all desert species could use precipitation from large rain event (47.6 mm in thisstudy) for quite a long time up to a few weeks. Both A. arenaria and A. Squarrosum were sosensitive to precipitation that they used rain water on the rain day, but H. ammodendron, C.mongolicum, N. tangutorum began to use rain water one day after the rain day. Comparing withthe large rain event, the small one (3-6 mm in this study) could also favor the developmentof desert plants but only in a relatively brief time up to couple days. C. Physiological Characters of Populus euphratica in different habitat forms: To study possible adaption strategy of P.euphratica to arid environment, stable isotoperatios in conjunction with other ecophysiological characteristics (e.g. photosynthesis character,leaf water potential) were measured. The stable isotope data suggest that P. euphratica uptakemainly groundwater recharged by Heihe river for development. The mature P. euphratica usedgroundwater for development while the saplings tended to use deeper soil water as complementto groundwater. Furthermore, the further the P. euphratica grows to the riverbank, the higherWUE that the individual plant has. The utility of river water by mature P. euphratica near the riverbank increasedsignificantly one week after the water transport event. But no significant increase was foundfor P. euphratica grown in the middle of forest and Gobi, 110 m and 250 m from riverbankrespectively. Water transport in Heihe river can favor the development and restoration of P.euphratica. The water transport with high quantity in relatively long time facilitated the growthofP. euphratica at Gobi far away (18 km) from the riverbank. The water transport with lowquantity in high frequency only facilitated the growth of P. euphratica near the riverbank. Thisfeedback of P. euphratica to water transport is also helpful for designing reasonable mode ofwater transport. D. WUE, water potential, photosynthetic rate of desert plants: Theδ~(13)C value of leaves were measured to evaluate the intrinsic water-use efficiency(WUE) of each plant. The predawn water potential (φ_(pd)) and midday water potential (φ_(md)) ofeach species were also measured. The ~(13)C measurements indicated that all plants have higher~(13)C value (high WUE) in arid month (July) of summer season and lower ~(13)C value (low WUE)in wet months (August and September). This variation was negatively consistent with the valueof water potential which was higher in August and September than that in July. The shrub C. mongolicum, which has higher evaporation rate and lower water utilizationefficiency than H. ammodendron, mainly use ground water (or deep soil water) freely.Consequently, Planting C. mongolicum in this area might exhaust groundwater. C. mongolicum will compete with H. ammodendron so severely that the restoration of H. ammodendron wasdelayed. P. euphratica and other species which also rely on groundwater for survival. Soreforestation with C. mongolicum might cause irreversible groundwater shortages and is not agood choice.
|
