Knowledge Resource Center for Ecological Environment in Arid Area
| 青藏高原典型生态系统优势植物水分利用来源及利用效率研究 | |
| 其他题名 | Plant water sources and water use efficiency of dominant species in typical ecosystems on the Tibetan Plateau |
| 段德玉 | |
| 出版年 | 2007 |
| 学位类型 | 博士 |
| 导师 | 欧阳华 |
| 学位授予单位 | 中国科学院地理科学与资源研究所 |
| 中文摘要 | 青藏高原因其对全球气候变化的极其敏感性和脆弱性，以及对中国、亚洲甚至全球气候变化的深远影响力而受到越来越多的关注。青藏高原自然地表的明显区域分异，引起了其植被从东南到西北呈水平地带性分布，但是对于植被地带性分布格局的主要环境影响或限制因子，目前研究还没有明确的认识。\n论文以青藏高原典型生态系统优势植物为研究对象。在青藏高原从南往北设置一条水平植被样带，沿样带分别在亚高山森林、高山灌丛、高寒草甸、高寒草原和荒漠灌丛植被中各选择一个定点观测样地。运用稳定性同位素技术，利用两项或三项分隔线性混合模型(two- or three-compartment linear mixing model)，研究了各样地不同来源水分对植物生长的相对贡献及其随环境气候条件改变而产生的时空差异，分析了不同植物水分利用效率以及其对气候变化的响应，并探讨了区域水分差异在引起植被水平地带性分布中的作用。\n青藏高原夏季降雨稳定同位素组成存在明显的时空差异。整个研究区域大气雨水线为：y = 6.72x - 5.39。那曲样地降雨稳定同位素值最低，格尔木样地最高。样带北部降雨同位素组成表现出了明显的降雨量效应，而南部则具有显著的温度效应。格尔木样地土壤水富集重同位素组分，且不同深度土壤水同位素值具有明显的分层现象，其它样地由于土层较薄，更容易受到降雨和蒸发的影响，一般表现为表层土壤水富集重同位素组分，而下层土壤水同位素值相对偏低。\n不同物种间植物组织水与区域内各来源水分同位素组成的相关性差异明显，表明植物利用不同来源的水分。格尔木样地唐古特白刺茎组织水同位素值接近地下水，二者具有一致的季节性变化趋势，而林芝样地高山松茎组织水同位素值与降雨有相似的变化趋势。拉萨样地川滇柳茎组织水、那曲样地小嵩草与五道梁样地紫花针茅根系抽提水同位素组成随时间波动较大，与区域各种水源没有固定关系，受当地降雨量影响明显。\n所研究的植物均使用各种来源水的混合水分。唐古特白刺主要利用来自于地下水的深层土壤水，雨水对唐古特白刺的平均贡献率只有14.6%。紫花针茅与小嵩草利用雨水与浅层地下水（地表径流）的混合水分，川滇柳主要使用来自河水的地下水。这三种植物对不同水源的利用率受降雨量影响，紫花针茅、小嵩草和川滇柳利用的水分平均分别有34.2%、43.2%和29.8%来自降雨。林芝高山松主要利用雨水，研究期间高山松利用水分平均有73.6%来自于降雨。\n一次性降雨后，土壤水同位素值都呈现先降低后回升的变化趋势，但是，不同样地降雨对土壤水所能影响的土层深度及其程度都存在较明显差异。一次性降雨后不同植物对雨水的利用率具有相同的时间变化趋势，但不同植物达到最大雨水利用率的时间不同。\n由于地下水、多年冻土等原因，各样地土壤含水量与区域年雨量并不具有一致的空间分布格局。唐古特白刺、紫花针茅叶片δ13C值表明了植物生长环境的干旱，五道梁样地低温也是造成紫花针茅叶片δ13C值偏高的重要原因，表明植物生长也同时受到低温的限制。小嵩草、川滇柳和川滇高山栎叶片δ13C值表明植物生长未受到明显的水分胁迫，且后者的水分利用表现出了一种相对浪费的模式。\n与植被分布一致，样带内植物叶片δ13C值也呈明显地带性分布。叶片δ13C值表明，亚高山阔叶植物、针叶植物、高寒灌木和高寒草甸的生长没有受到明显的水分限制，水分条件不是限制植物生长的主要环境因子。高寒草原与荒漠灌木植物叶片δ13C值表明这两种植物生长环境的干旱，植物生长可能受到了当地水分供应条件的限制。并且，不同植物叶片δ13C值随区域年降雨量变化的幅度不同，表明不同植物所受到的水分胁迫程度具有地带性的差异。降雨量不同引起的区域水分条件的差异，是引起青藏高原不同地区植物叶片δ13C值差异的更重要原因。 |
| 英文摘要 | The Tibetan Plateau is being paid more and more attention due to its susceptibility to global climate change and great influence on Chinese, Asian and even whole global climate changes. Vegetation distribution on the Tibetan Plateau displays significant zonal heterogeneity, therefore typical alpine vegetation zones of forest, shrub, meadow, steppe and desert appear in succession from the southeast to the northwest on the Tibetan Plateau. However, unanimous idea is still not reached now on how the environmental variables controlled the distribution patterns, and which variables take more important role in limiting plant species distribution.\nA vegetation transect was setup from the south to the north of the Tibetan Plateau. One research site was selected in each of the five typical vegetations (submoutain forest, alpine shrub, alpine meadow, alpine steppe and desert shrub) along the transect. Survey and sampling were carried out during the growth season. Combined with meteorologic data, δ2H and δ18O of plants xylem water, soil water, groundwater and precipitation were analyzed to determine water sources of dominant plant species in different ecosystems using two- or three-compartments linear mixing models. The changes of plant water sources with environmental variables were also studied. Plant leaf δ13C values were measured to determine plant water use efficiency and its response to precipitation, temperature and other environmental variables. Based on all the results, the research will determine preliminarily the contributions of regional water conditions to zonal vegetation distribution on the Tibetan Plateau.\nObvious temporal and spatial difference was observed for precipitation δ2H and δ18O values on the Tibetan Plateau. The meteoric water line of summer precipitation in the study areas was y = 6.72x - 5.39. The most negative precipitation isotopic values occurred in Naqu plot while the most positive appeared in Golmud plot. Significant precipitation effect was observed for rainwater isotope values in the north of the transect, however, there was obvious temperature effect in the south. Soil water in Golmud plot had the most positive isotopic values among the five plots and displayed clear isotope value gradient among different depth of soil, which was not observed in other plots.\nThere were different correlations among species between plant xylem water and source water isotope composition, indicating that plants use different water sources. Isotopic values of Nitraria tangutorum Bobr. xylem water were similar to groundwater, and both of them had the same seasonal changing trend in Golmud. Xylem water isotopic values of Pinus densata Mast. had the same seasonal trend with precipitation. Isotope values of water extracted from roots of Stipa purpurea Griseb and Kobresia pygmaea Clarke and stems of P. tabulaeformis varied greatly among sampling time. No clear correlation was found between plant water and source water isotopic values, depending on the amount of precipitation. \nN. tangutorum mainly used deep soil water from groundwater, and mean relative contribution of precipitation to plant growth was only 14.6% in the whole growth season. S. purpurea and K. pygmaea used the mixed water of precipitation and shallow groundwater, and S. rehderiana mainly used groundwater from the river nearby. However, utilization to different sources by the three dominant species was influenced strongly by the amount of regional precipitation. 34.2%, 43.2% and 29.8% of plant xylem water of S. purpurea, K. pygmaea and S. rehderiana were from precipitation respectively. P. densata mainly used rainwater and 73.6% of xylem water derived from precipitation during the growth season.\nSoil water isotope values decreased quickly and then increased gradually after experiencing a medium precipitation event. However, the influence of precipitation on different depth of soil water isotopic values was different among the study areas. Rainwater use ratios by different species changed similarly after the precipitation event, however, different plants spent different time to reach maximum rainwater use ratios after the event. \nSpatial distribution of soil moisture is different significantly from that of precipitation due to regional groundwater and permafrost. Leaf δ13C values of N. tangutorum and S. purpurea showed that the species experienced some water stress. No obvious water stress was observed for the growth of P. densata, S. rehderiana and K. pygmaea. Moreover, Q. aquifolioides use water lavishly because of sufficient rainwater in Linzhi plot.\nJust like vegetation distribution patterns along the transect on the Tibetan Plateau, leaf δ13C values of different dominant plants along the transect showed a clear zonal difference, indicating that the growth of the species along the transect experienced different water stress. Moreover, the regression slope between leaf δ13C values and regional annual precipitation increased from the south to the north along the transect, indicating water stress is more and more serious for the plants from the south to the north. There is no obvious correlation between leafδ13C values and precipitation for submontane broad-leaved, boreal forest species, alpine shrub species and alpine meadow species, indicating that plant growth was not stressed by water supplies. However, significant correlation between leafδ13C values and precipitation for alpine steep and desert shrub species showed that growth of the plants must be limited by water supplies. Our results suggested that zonal variations in leaf δ13C values along the transect were caused mainly by regional water conditions. Zonal vegetation distribution patterns on the Tibetan Plateau are the results of long-term adaptation of plant species to local climate conditions, and variations in water supplies caused by different annual precipitation are mainly responsible for the patterns. |
| 中文关键词 | δ2H、δ18O、δ13C ; 水分利用来源 ; 水分利用效率 ; 植被地带性分布 ; 植被样带 ; 青藏高原 |
| 英文关键词 | δ2H δ18O δ13C plant water sources water use efficiency zonal vegetation distribution vegetation transect the Tibetan Plateau |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院地理科学与资源研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286531 |
| 推荐引用方式 GB/T 7714 | 段德玉. 青藏高原典型生态系统优势植物水分利用来源及利用效率研究[D]. 中国科学院地理科学与资源研究所,2007. |
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