Knowledge Resource Center for Ecological Environment in Arid Area
| 准噶尔盆地南缘荒漠植物对小降雨事件的生理响应 | |
| 其他题名 | Physiological responses of desert plants to small rainfall events at the south periphery of Junggar Basin |
| 吴玉 | |
| 出版年 | 2014 |
| 学位类型 | 博士 |
| 导师 | 李彦 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 水是荒漠植物生存和生长的关键限制因子。小降雨事件(<5 mm)在准噶尔盆地年降雨频次中占有很大比重(>80%)，并且发生间隔较短(<10 d)。相比于偶发的、难以预测的大降雨，小降雨可能是干旱区植物较稳定的水源之一。曾有研究显示雾、露等叶湿润事件中，一些植物可通过叶片吸收水分。本研究将思路拓展到小降雨上，拟揭示荒漠植物对小降雨事件可能的利用策略。实验在准噶尔盆地南缘原始生境中开展，模拟了1 mm和6 mm人工降雨，通过原位监测的方法对比了4种植物功能型(短生活史草本植物、长生活史草本植物、非潜水灌木和潜水灌木)共28种植物对大、小降雨的生理响应。 结果表明，多数草本植物的净光合速率(PN)、气孔导度(gs)和蒸腾速率(Tr)在1 mm降雨过后保持稳定或增加，但增幅小于6 mm降雨，瞬时水分利用效率(WUE)即使在6 mm降雨下所受影响也不大。对灌木来说，1 mm降雨过后，PN的响应种间差异较大，gs和Tr不变或增加，WUE保持恒定或显著降低到与6 mm降雨接近的水平。用“相对有效性”衡量1 mm降雨的效应，发现非潜水灌木的gs-相对有效性和潜水灌木的WUE-相对有效性分别高达71.8%和76.5%。实验结果证实了荒漠植物能够利用小降雨提供的水分。 1 mm降雨不能被植物根系吸收，故叶面吸水可能是有效的途径。本研究对各物种的离体叶片进行了吸水能力测试。按照植物功能型、植物生活型、叶面类型和叶质地属性将植物分类，对比各分类单位的单位面积叶片吸水量(LWUC)和叶片相对含水量增量(Rw)。结果显示草本植物的LWUC和Rw比灌木高。进一步用关联度分析法寻找植物功能性状与植物对小降雨响应之间可能的联系，发现叶面毛的疏密程度与植物蒸腾作用关系较大。叶面毛可以截留水分供植物直接吸收，或通过影响蒸腾耗水而在荒漠植物利用小降雨中起到积极作用。在所研究的物种当中，多数草本植物有叶面毛而多数灌木无叶面毛，因此草本植物和灌木可能分别直接和间接地从小降雨事件中获益。 为了解不同降雨模式对植物生理特性和生物量分配的影响，以4种一年生草本植物地肤(Kochia scoparia)、滨藜(Atriplex patens)、盐角草(Salicornia europaea)、短柱猪毛菜(Salsola lanata)为研究对象，测定其在不同人工降雨模式下，叶片光合特性和生物量分配情况。在温室中模拟了4种降雨模式，即在湿润和干旱两种条件下分别施行每周两次小降雨和总水量相等的一次大降雨。结果发现降雨量主导着植物总生物量和各部分生物量，而降雨频次增多趋使植物加大对地下生物量的分配。本研究主要结论为：小降雨对荒漠植物具有生理有效性，对维持荒漠生态系统的生物多样性具有重要意义；植物在不同降雨模式下表现出光合响应和生物量分配对策。研究结果有助于我们理解并预测全球变化背景下，荒漠植物对降雨变化的生理响应和形态适应。 |
| 英文摘要 | Water is a key limiting factor for surviving and growth of desert plants. Small rainfall events (<5 mm) account for a large proportion (>80%) of annual precipitation frequency with short intervals (<10 d) in Junggar Basin. Compared to occasional and unpredictable large rainfall, small rainfall might be a stable water source for plants in arid region. Previous researches showed that some plants can absorb water via leaves during leaf wetting events which result from fog or dew. This research expands to small rainfall events, and the purpose is to elucidate the possible strategy for desert plants to utilizing small rainfall events. The study investigated the physiological responses of 28 species to 1 mm and 6 mm simulated rainfalls in the field of the south edge of the Junggar Basin. For comparison, species were grouped into four plant functional types: short lifecycle herbs, long lifecycle herbs, non-phreatophyte shrubs and phreatophyte shrubs. The results showed that, the net photosynthetic rate (PN), stomatal conductance (gs) and transpiration rate (Tr) were stable or increased in most herbs after 1 mm rainfall, but the increase was less than those seen after 6 mm rainfall. The instantaneous water use efficiency (WUE) were generally less affected, even after 6 mm rainfall. For shrubs, after 1 mm rainfall, the PN responses varied between species and gs and Tr were unchanged or increased. WUE were either constant or were significantly reduced to levels that were similar to those seen after 6 mm rainfall. The “relative effectiveness” were used to evaluate how effective a 1 mm rainfall was. And we found that the gs-relative effectiveness of non-phreatophyte shrubs and the WUE-relative effectiveness of phreatophyte shrubs were up to 71.8% and 76.5%, respectively. The results demonstrated that water of small rainfall could be utilized by desert plants. 1 mm rainfall could not be absorbed by roots, thus the foliar water uptake was the possible effective way, and the foliar water uptake capacities of excised leaves from all species were assessed. We compared leaf water uptake content (LWUC) and percentage increase in leaf water content (Rw) within plant functional types, plant life forms, leaf surface traits and leaf texture attributes. And the results showed that LWUC and Rw of herbs were higher than those of shrubs. Then the association degree analysis was used to find possible relationships between plant functional traits and plants’ response to small rainfall. The results exhibited that large association degree existing in absorbent trichomes density and transpiration rate. Trichomes can intercept water for plants absorption directly, or play positive role in plants utilizing small rainfall through affecting water consume during transpiration. Of all the studied species, most herbs have trichomes while most shrubs have no trichomes, thus herbs and shrubs might be beneficial from small rainfall events directly and indirectly, respectively. To understand the effect of different precipitation patterns on physiological characteristics and biomass allocations, the photosynthesis and biomass allocations of four annuals (Kochia scoparia, Atriplex patens, Salicornia europaea and Salsola lanata) were investigated in greenhouse conditions. Four precipitation patterns were simulated: two small rainfall events versus one large rainfall event with equivalent total water amount which were applied weekly under wet and drought conditions, respectively. The results implied that total rainfall amount dominated total biomass and the biomass allocations, while more rainfall frequency tends to allocate more belowground biomass. In conclusion, small rainfall events have physiological effects on desert plants and have important implications in maintaining biological diversity of desert ecosystems. Meanwhile, the desert plants showed photosynthetic responses and biomass allocation strategies under different precipitation patterens. The study im |
| 中文关键词 | 小降雨 ; 植物功能型 ; 叶面吸水 ; 叶面毛 ; 光合速率 ; 气孔导度 |
| 英文关键词 | Small rainfall events Plant functional types Leaf water uptake Trichomes Photosynthetic rate Stomatal conductance |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院新疆生态与地理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287431 |
| 推荐引用方式 GB/T 7714 | 吴玉. 准噶尔盆地南缘荒漠植物对小降雨事件的生理响应[D]. 中国科学院大学,2014. |
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