【作者】 邓文红；

【导师】 沈应柏；

【作者基本信息】 北京林业大学 ， 植物学， 2016， 博士

【摘要】 在长期的自然群落演替过程中,黑沙蒿(Artemisia ordosica)逐渐成为我国沙地群落中的主要建群种,随着黑沙蒿种群的不断扩大,沙地固定早期的一些先锋植物逐渐退出群落,并且黑沙蒿群落中生物多样性较低。尽快修复沙化土地是我国生态建设的艰巨任务。因此,深入研究黑沙蒿群落的形成及演替的生态学规律对沙漠化防治具有非常重要的意义。在宁夏盐池荒漠生态系统定位研究站黑沙蒿标准样地内,选择极低盖度、低盖度、中盖度和高盖度植物4块样地,对其群落特征、物种组成以及土壤含水量进行了研究。在此基础上以样地内自然生长的黑沙蒿为材料,对其化感物质的种类、释放途径、化感作用在群落演替过程中的作用以及化感作用机理进行了较系统的研究。主要研究结果如下：(1)在沙地固定过程中,植物平均高度和平均盖度逐渐增加,物种多样性指数和丰富度指数表现出先升高后降低的过程,黑沙蒿种群不断扩大,最终形成单优势种群落,沙蓬(Agriophyllum squarrosum)、虫实(Corispermum hyssopifolium)、草木樨状黄芪(Astragalus melitodes)逐渐退出植物群落,狗尾草(Setaria viridis)成为黑沙蒿群落的伴生种,4块样地中,除了低盖度样地40-60cm深度的土壤含水量显著高于同一深度其它盖度植物样地的土壤含水量,其它均无显著性差异。(2)在单因素试验的基础上,以气相色谱质谱(GC-MS)峰面积为考察指标,采用3因素(浸提时间、浸提温度、固液比)3水平的正交试验对黑沙蒿根、茎、叶、种子水提取液化学物质的提取方法进行了研究。实验结果表明,根、茎、叶、种子的最佳提取条件分别为：48 h、40℃、1：5,48 h、40℃、1：40,72 h、40℃、1：50,72 h、40℃、1：5。单因素试验和正交试验检测出的物质种类相同,但正交试验检测出的化学物质的含量明显高于单因素试验。正交试验对黑沙蒿化学物质的提取效率高于单因素试验,可以大大提高黑沙蒿中化学物质检测的可靠性。(3)在最佳提取条件下,提取了黑沙蒿根、茎、叶、种子及土壤中的非挥发性化学物质,利用GC-MS对其进行了分析测定。其中检测到的酸性物质35种,主要为小分子有机酸、酚酸和脂肪酸类物质；碱性物质6种,为吗啉、胺类、尿素、嘧啶等；中性物质20种,为烯、炔、醇、酮、酯、醛、呋喃、红没药醇氧化物等。并测定了黑沙蒿根提取液的酸性组分、碱性组分和中性组分对沙蓬种子萌发的影响,结果表明：酸性组分对沙蓬种子萌发的抑制作用最强,说明黑沙蒿水提取液中的化感物质主要为酸性物质。(4)分别测定了三个浓度(0.05 g FW·ml-1、 0.10g FW·mL-1、 0.20 g FW·mL-1)的黑沙蒿根、茎、叶、种子水提取液对黑沙蒿、沙蓬、虫实、草木樨状黄芪和狗尾草种子萌发、幼苗生长以及生物量的影响。结果表明：黑沙蒿提取液对黑沙蒿、沙蓬、虫实、草木樨状黄芪表现为抑制作用,狗尾草表现为促进作用。黑沙蒿各部位提取液均表现出对黑沙蒿根生长的自毒作用最强,其中黑沙蒿叶和茎提取液对根长生长的影响最大,说明黑沙蒿的自毒作用主要是影响根的生长,自毒物质主要来自于地上部枝叶的雨水淋洗或枯枝落叶的腐解。黑沙蒿释放出的化学物质强烈的影响沙蓬、虫实、草木樨状黄芪从种子萌发到生长发育的整个生命过程,且随着提取液浓度的增加而增强。其中根的生长受到的抑制作用最强,说明黑沙蒿释放出的化学物质进入到土壤中,首先影响伴生植物根系的生长。黑沙蒿各部位水提取液对狗尾草种子萌发、幼苗生长以及生物量的积累均表现为促进作用。且随着提取液浓度的增加而增强,达到最大值后,随着提取液浓度的继续增加,促进作用减弱,但在整个测试浓度范围内,均表现为促进作用。(5)采用动态顶空活体采样,热脱附气相色谱质谱联用仪(TCT-GC-MS)收集和测定了黑沙蒿释放出的挥发性有机化合物(VOCs),共检测出23种挥发物。主要为萜烯类物质。生长季中,根释放的主要物质为石竹烯、2-乙基己醇、柠檬烯等：茎叶释放的主要物质为柠檬烯、罗勒烯、3-蒈烯等。成熟季中,根释放的主要物质为石竹烯;茎叶释放的主要物质为柠檬烯、罗勒烯、β-蒎烯、β-水芹烯等。在干燥器中(直径30 cm、高50 cm),分别测定了加入5个体积(0.10 mL、0.25 mL、0.50 mL、1.00mL、2.00 mL)的柠檬烯标准品对沙蓬和虫实种子萌发和幼苗生长的影响,结果表明：柠檬烯对沙蓬种子萌发、幼苗生长以及生物量的积累均有显著的抑制作用,且随着浓度的增加,抑制作用增强。柠檬烯对虫实的影响表现出“低促高抑”的过程。(6)黑沙蒿根和茎提取液处理沙蓬、虫实、草木樨状黄芪、狗尾草幼苗后,用非损伤微测技术(NMT)测定了植物根系吸收K+和NH4+的情况。结果表明：黑沙蒿根和茎提取液处理沙蓬、虫实、草木樨状黄芪幼苗后,引起K+和NH4+外流；而狗尾草幼苗受到黑沙蒿根和茎提取液处理后,K+和NH4+内流。黑沙蒿提取液对4种受试植物的影响主要是通过NH4+实现的。综合以上结果,本文得出以下结论：黑沙蒿植株能够释放化感物质来影响共生植物种子萌发和幼苗生长发育,从而对群落的植物组成和分布格局产生影响,因此,在黑沙蒿群落的形成以及演替过程中,化感作用起着非常重要的作用。更多还原

【Abstract】 Artemisia ordosica has gradually become the dominant species of the sand community in the process of plant succession. Some of early pioneer plants in the stabilization process of sand dunes have gradually withdrawed from the community and has a lower biodiversity with the continuous expansion of A. ordosica population. Repair desertification of land as soon as possible is the formidable task of ecological construction in our country. Therefore, the further research of ecology laws during the formation and succession of A. ordosica community plays a very important meaning in prevention and control of desertification. In this thesis,4 plots (very low coverage, low coverage, middle coverage and high plant coverage) were selected in standard plot of A。 ordosica of desert ecosystem research station in Yanchi County, Ningxia Hui Autonomous Region and the community characteristics, species composition and soil water contents were studied. On the basis of these, species of allelochemicals, release approach, allelopathy in the process of community succession and the allelopathy mechanism of A. ordosica had been a systematic researched. The main conclusions are as follows:(1) In the process of sand fixation, The average height and average coverage of plants gradually increased, Shannon-Weiner index and Simpson index showed an increase and then decrease trend. The population of A. ordosica was expanding constantly, and ultimately a single dominant species population was formed. Agriophyllum squarrosum、 Corispermum hyssopifolium、 Astragalus melitodes gradually exited plant community and Setaria viridis became a companion species of A. ordosica community. There were no significant difference except the soil moisture contents of 40-60 centimeters depth of the low coverage sample were significantly higher than those of the other plant samples with the same depth.(2) On the basis of single factor experiment, Method of aqueous extraction of chemical substances in roots, stems, leaves and seeds from A. ordosica were studied using the three factors (extraction time, extraction temperature and solid-liquid ratio) 3 levels orthogonal experiment and the chemical substances of extracting solution were detected by gas chromatography mass spectrometry (GC-MS). The results showed that the best extraction conditions in roots, stems, leaves and seeds were: 48 h、 40℃、 1:5,48 h、 40℃、 1:40,72 h、 40 ℃、1:50,72 h、 40℃、 1:5. The chemical substances detected by single factor test and orthogonal test were the same, but the contents of the orthogonal test were significantly higher than those of the single factor test. The extraction efficiencies of chemical substances from A. ordosica using the orthogonal experiment were higher than those of the single factor test and the reliability of chemicals detection could greatly be improved.(3) The non-volatile chemical substances were extracted from the roots, stems, leaves, seeds of A. ordosica and soil under optimal extraction conditions. The extracts were analyzed by GC-MS and detected 35 acidic organic compounds,6 alkaline organic compounds and 20 neutral organic compounds. They were phenols, low-molecular-weight organic acids and fatty acids in acidic substances, morpholine, amine, urea and pyrimidine in alkaline substances and alkene, alkyne, alcohol, ketone, ester, aldehyde, furan and bisabolol oxide in neutral substances. Then inhibitory activities of acidic, alkaline and neutral components of root extraction from A. ordosica on the germination of A. squarrosum were evaluated using the petri dishes method. The results showed that inhibitory effect of acidic components on the germination of A. squarrostm was the strongest. So the allelochemicals of aqueous extracts from A. ordosica were mainly acidic organic compounds.(4) Seed germination, seedling growth and dry mass tests from the five test species (A. ordosica, A. squarrosum, C. hyssopifolium, A. melitodes, S. viridis) were conducted with aqueous extracts of 3 concentration (0.05,0.10 and 0.20 g FW-mL-1) from the roots, stems, leaves and seeds of A. ordosica. The results showed that A. ordosica extracts had inhibitory effects on seed germination, seedling growth and dry mass of A. ordosica, A. squarrosum, C. hyssopifolium and A. melitodes. On the contrary, A. ordosica extracts had promotion effects on seed germination, seedling growth and dry mass of S. viridis. Autointoxication of aqueous extracts from the roots, stems, leaves and seeds of A. ordosica on root growth was the highest. In general, the inhibitory effects of extracts from leaves and stems were more pronounced than those of roots and seeds extracts. These illustrated that the autointoxication of A. ordosica mainly influenced the growth of root. Autotoxins chemicals mainly came from stems and leaves by rainfull or decomposition of litters. The chemical substances releasing from A. ordosica had noteworthy effects on A. squarrosum, C. hyssopifolium and A. melitodes in the whole course of an individual’s life, from seed germination to growth and development, and the effects increased with higher concentration of extracts. Among them, the growth of roots was the strongest inhibitory effects. These illustrated that the chemical substances into the soil first influenced the growth of roots of associated plant roots. The aqueous extracts of A. ordosica significantly promoted seed germination, seedling growth and dry mass of S. viridis, and the effects increased with higher concentration of extracts. After reaching the maximum, the promoting effects were decreased when concentrations were increased. But extracts of all parts of A. ordosica in test concentration range had positive effects.(5) Volatile organic compounds (VOCs) from A. ordosica under different growth seasons were collected using dynamic headspace collection methods and identified by TCT-GC-MS. The results indicated that terpenes were the dominant VOCs releasing from A. ordosica, in which had 23 VOCs. The main volatiles releasing from roots in the growing season were caryophyllene,2-ethyl hexanol, Limonene et al, and those of stems and leaves were Limonene, ocimene,3-carene et al. The main volatile releasing from roots in the mature season was caryophyllene, and those of stems and leaves were Limonene, ocimene, β-pinene, β-phellandrene et al. Seed germination and seedling growth tests from A. squarrosum and C. hyssopifolium were conducted with Limonene of 5 volume (0.10 mL,0.25 mL,0.50 mL,1.00 mL,2.00 mL) in dryer (diameter of 30 cm, height of 50 cm). The results indicated that the volatile of Limonene had significant negative effects on seed germination, seedling growth and dry mass of A. squarrosum, and the inhibitory effects increased with higher concentrations of volatile of Limonene. The volatile of Limonene displayed allelopathic effects on C. hyssopifolium and the effects were concentration-dependent. The effects of Limonene were positive on seed germination, seedling growth and dry mass when the concentrations of Limonene were low and negative when the concentrations were high.(6) The K+and NH4+ flux were measured in seedling roots of the four associated herbaceous plants(A. squarrosum, C. hyssopifolium, A. melitodes, S. viridis) using non-invasive micro-test technique (NMT) after being treated with the extracts of roots and stems from A. ordosica. The results indicated that exposure of roots (A. squarrosum, C. hyssopifolium, A. melitodes) to extracts from A. ordosica induced outflow of K+and NH4+, but inflow in S. viridis. The extracts of A. ordosica mainly influenced the absorption of NH4+.According to these results, this paper draws the following conclusions:A. ordosica can release the allelochemicals to influence the symbiotic plant seed germination, seedling growth and development, thus affecting the plant composition and distribution pattern. Therefore allelopathy plays a very important role.更多还原