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荒漠建群种梭梭和白梭梭对降水的再分配及其生态意义研究
戴岳
学位类型博士
导师李彦
2015
学位授予单位中国科学院大学
学位授予地点北京
学位专业生态学
关键词梭梭属植物 穿透降水 树干茎流 生理生态响应 个体形态调节 稳定性同位素 水分来源
摘要水是荒漠生态系统的首要限制因素,影响着生态系统生态过程的各环节。在干旱区,降水和地下水是植物可利用的两个重要水源。降水在灌丛干扰下以穿透雨和树干茎流的方式到达地表,影响了降水在植被冠层下的入渗以及再分配,对荒漠植被的生存和生长具有重要意义。然而,仅凭降水无法满足一些植物正常的生长需求,地下水成为植物用水的重要组成部分。近50年来,全球气候变化以及人类活动的加剧,导致古尔班通古特沙漠的降水与地下水位正在发生显著的改变,这些改变正导致荒漠植物水分利用的适应性变化。本研究以古尔班通古特沙漠的建群种梭梭(Haloxylon ammodendron)和白梭梭(Haloxylon persicum)为对象,从冠层对降水的再分配过程、梭梭和白梭梭对去除降水再分配分量(穿透降水、树干茎流)的生理响应和个体形态调节以及梭梭和白梭梭的水分来源三个方面研究这两个物种在水分受限的荒漠环境中对各自生境的适应。 结果表明,2012年和2013年生长季,在梭梭和白梭梭的冠层对降水的再分配过程中,穿透降水、树干茎流量和截留量与降水量均呈显著的线性正相关(p<0.001);穿透降水占总降水的比例最大。自然降水条件下,梭梭、白梭梭的穿透降水分别占降水总量的61.6%、73.5%;树干茎流分别占降水总量的7.3%、5.7%;截留量分别占降水总量的31.0%、20.8%。梭梭和白梭梭形成树干茎流的最小降水量为0.8 mm。梭梭的集流率变化范围在1.72–128.91,白梭梭的集流率变化范围在0.12–122.71。梭梭表现出更强的产生树干茎流的潜力,意味着极端降水事件增多时,梭梭能够将更多的降水储存在土壤深层,以备干旱时使用。 为了研究梭梭和白梭梭对去除降水再分配分量(穿透降水、树干茎流)的生理响应和个体形态调节,实验共设置4种降水处理,即去除穿透降水处理、去除树干茎流处理、同时去除穿透降水和树干茎流处理以及自然降水处理。2011–2013年生长季,4种降水处理下,梭梭的生理响应不显著,而个体形态调节各处理间差异显著。穿透降水和树干茎流的去除在生长季中后期减缓了梭梭同化枝的生长,加速了同化枝脱落,这种影响在大的降水脉冲后表现更为明显。梭梭通过脱落同化枝以维持生理稳定性。2012和2013年生长季,在不同降水处理下,白梭梭的生理响应和个体形态调节没有显著差别,但是同时去除穿透降水和树干茎流的处理对白梭梭造成一定的水分胁迫,在生长季中后期引起白梭梭的叶水势、光合能力、同化枝的生长速率降低。白梭梭对穿透降水和树干茎流缺失的响应没有梭梭表现的强烈,表明降水条件变化时,梭梭能更快地做出调整。 2013年生长季,应用稳定性同位素技术研究了梭梭和白梭梭的水分利用动态以及这两个物种对夏季大的降水脉冲引起的土壤水分脉冲的响应。结果表明,生长在丘间低地的梭梭和生长在沙丘顶部的白梭梭有着不同的水分来源。这两种植物对不同水源的吸收具有明显的季节转换现象:在表层土壤含水量充足的早春季节,梭梭主要利用浅层土壤水(0–40 cm)而白梭梭主要利用中层土壤水(40–100 cm);在表层土壤含水量亏缺的夏季,梭梭主要利用地下水而白梭梭主要利用深层土壤水(100–300 cm)。夏季大的降水脉冲后,梭梭和白梭梭都增加了对浅层土壤水的利用,但梭梭仍主要利用地下水而白梭梭主要利用深层土壤水。 本研究表明,梭梭和白梭梭对降水具有汇聚、储存进而延后利用的功能。这两个物种通过“自集水”增强对水分亏缺的抵抗能力,提高对降水的利用效率以适应干旱缺水的环境。因此,梭梭和白梭梭群落能够承受一定程度的干旱和气候变化,在自然条件下保持相对的稳定。也就是说,梭梭、白梭梭对降水的再分配具有重要的生态意义。
其他摘要In desert environments, water is the principal factor limiting the ecological processes, and precipitation and groundwater are two primary water sources for plants. Precipitation is partitioned into throughfall and stemflow by canopy during reaching the ground, which alter water infiltrition and redistribution and play a crucial role on survial and growth of plants. However, precipitaion can hardly satisfy the growth needs of plants, and groundwater is another important water source for plants. Within the current background of global climate change, significant increase in precipitation has been recorded in the arid region of central Asia over the past 50 years. In addition, in the transition region between the Gurbantonggut desert and oases, the groundwater table has fallen significantly as a result of the overexploitation of groundwater. All these changes would definitely lead to the changes of plant water usage in this region. Haloxylon ammodendron and Haloxylon persicum are the dominant species in the Gurbantonggut desert. This study aims to investigate precipitation partitioning by canopy of H. ammodendron and H. persicum; and the responses of H. ammodendron and H. persicum when throughfall and stemflow were eliminated, from the perspective of ecophysiological activities and morphological adjustment of individuals. The dynamics of water use of these two species were also studied. The results showed that, during the growth season of 2012 and 2013, throughfall, stemflow and interception increased linearly with the increasing precipitation amount (p<0.001). Throughfall accounted for the largest percentage of total precipitation. Based on the observation from the natural precipitation, the average throughfall in H. ammodendron and H. persicum was 61.6% and 73.5% of total precipitation, respectively. The average stemflow in H. ammodendron and H. persicum was 7.3% and 5.7% of total precipitation, respectively. Interception in H. ammodendron and H. persicum was 31.0% and 20.8% of total precipitation, respectively. Stemflow occurred when total amount of precipitation was more than 0.8 mm for both shrubs. Funneling ratios of H. ammodendron were in the range of 1.72–128.91, and in the range of 0.12–122.71 for H. persicum. H. ammodendron showed greater potential than H. persicum in collecting stemflow, which means that H. ammodendron has the capacity to store more precipitation water in the deep soil layer to cope with the drought. In order to investigate response of H. ammodendron and H. persicum to variation in precipitation partitioning (throughfall and stemflow), the experiments were carried out under natural precipitation and manipulated precipitation treatments (no throughfall, no stemflow, and no throughfall and no stemflow, respectively). During the growing season of 2011 to 2013, the branch water potential, chlorophyll fluorescence parameters and photosynthetic parameters of H. ammodendron appeared to be insensitive to precipitation changes, but the branch growth rate differed significantly among four precipitation treatments. Assimilating branches under the treatment of no throughfall, no stemflow, and no throughfall and no stemflow had slower growth or earlier defoliation than natural precipitation treatments in the middle or late growing season, especially after the large precipitation pulses. The result showed that efficient morphological adjustment of H. ammodendron individuals contributes to its maintenance of photosynthesis and acclimation to variation in water condition. During the growing season of 2012 and 2013, the branch water potential, chlorophyll fluorescence parameters, photosynthetic parameters of H. persicum showed no significant difference among four treatments, and its individual morphological adjustment appeared to be insensitive to precipitation changes. However, treatments of no throughfall and no stemflow resulted in lower branch water potential, photosynthesis capacity and the more defoliation of assimilating branches, implying that it may have an impact on growth of H. persicum. H. persicum was less sensitive to the removal of throughfall and stemflow than H. ammodendron, implying that H. ammodendron has a quicker response to the precipitation change than H. persicum. During the growth season of 2013, we used stable oxygen isotopes to study the dynamics of water usage of two Haloxylon species and their responses to the soil water fluctuations resulted from summer precipitation. H. ammodendron growing on inter-dune and H. persicum growing on the adjacent dune crest had distinct water use patterns and were able to shift water utilization according to the upper soil water content: when the upper soil water content was abundant in early spring, H. ammodendron mainly used shallow soil water(0–40 cm) while H. persicum mainly used middle soil water(40–100 cm); when the upper soil water content was depleted in summer, H. ammodendron mainly used groundwater while H. persicum mainly used deep soil water(100–300 cm). H. ammodendron and H. persicum increased utilization of upper water sources following the relatively large summer precipitations. However, H. ammodendron mainly took up groundwater and H. persicum mainly deep soil water. In conclusion, H. ammodendron and H. persicum have the ability to collect, store and utilize precipitation water. Both species enhanced their resistance to water deficiency, and improved precipitation use efficiency by “autonomous water collection”. Therefore, H. ammodendron and H. persicum could tolerate a certain degree of drought and climate change, and maintain the stability of communities under natural conditions. Namely, the redistribution of precipitation water by these two species is ecological important.
学科领域生态学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14605
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
戴岳. 荒漠建群种梭梭和白梭梭对降水的再分配及其生态意义研究[D]. 北京. 中国科学院大学,2015.
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