黄土高原典型草原针茅群落封育演替进程中的植物-土壤反馈机制研究

发布时间：2018-03-24 14:31

  本文选题：封育　切入点：植被演替　出处：《西北农林科技大学》2017年博士论文

【摘要】：围栏封育是草原经济有效的管理措施,被广泛应用于黄土高原退化草地的恢复管理过程中。封育排除了放牧、刈割等人为干扰对草地生态系统的影响,使得退化草地开展朝良性方向的自然恢复进程,体现在封育后草地盖度、生产力的增加和土壤结构、肥力和微生物活动的改善与提高,同时伴随植物群落结构的调整和物种多样性的变化。植物和土壤作为草地生态系统的两大主要组成部分,两者间的反馈作用是草地自然恢复进程中植被群落演替的重要驱动力,这使得针对草地长期封育演替进程中的植物-土壤反馈机制的研究具有重要的理论价值和实践意义。因为黄土高原地区宁夏云雾山典型草原在长达35 a的封育演替进程中已发生明显植被格局变化,本试验选取具有优势种更替现象的针茅群落作为研究对象,结合野外和室内试验,对封育演替时间序列草地根系特征、优势种针茅凋落物分解特性、针茅植物生长规律对土壤生物和非生物特性变化的响应特征及针茅的植物-土壤反馈效应指数进行了分析。主要研究结果如下:(1)在草地长期封育演替进程中,草地根系生物量和根系形态特征分别增加49.65%和94.80%,并伴随土壤水分和养分含量的增加,草地根系物种丰富度下降37.11%。草地根系特征在不同功能组的分配比例及其对封育措施的响应存在较大差异,表现为长期封育使得禾草类植物所占草地根系群落比例由41.65%升高至81.22%,其中多年生根茎型禾草根系指标增加幅度达10倍以上,这与禾草类植物根系较大的比根长和比根面积特征及其所受土壤C、N资源的促进作用密不可分;相比之下,非禾草类植物根系所占比例呈不断下降规律,且其根系特征主要受土壤P资源影响。(2)随着草地封育演替年限的增加(0、5、9、22和30 a),针茅根系生物量和根系形态特征分别增加87.29%和119.73%,且其物种组成格局发生明显变化,表现为长芒草根系比例由封育初期的77.12%,逐渐降至封育22 a草地的13.42%,并消失于封育30a草地;大针茅根系比例自封育初期的22.88%逐渐增加并在封育22 a草地达到86.58%,之后迅速下降;甘青针茅出现于封育30 a草地,并占据高达77.22%比例的优势地位。(3)为期2 a野外分解试验结果显示,针茅叶片和根系凋落物在分解末期的质量损失率平均分别为36.07%和32.00%,叶片凋落物中大针茅分解速率最高,根系凋落物中则为甘青针茅分解最快。3种针茅凋落物分解过程中元素变化规律相似,但受凋落物类型影响,其中叶片凋落物C含量平均由452.24 g·kg-1降低至440.21 g·kg-1,根系凋落物C含量则平均由420.73 g·kg-1升高至435.09 g·kg-1;叶片和根系凋落物N含量波动式下降,使得其C/N比值波动式上升;叶片凋落物P含量平均由0.29 g·kg-1升高至0.58g·kg-1,根系凋落物P含量则平均由0.30 g·kg-1波动式下降至0.26 g·kg-1。三种针茅的叶片和根系凋落物C、N和P元素均呈释放模式,且释放比例分别在23.78%-39.28%、37.20%-60.38%和21.30%-52.28%之间。相关分析表明,凋落物分解速率与其初始N含量呈正相关,并与初始C/N比值为负相关。(4)3种针茅表现出明显植物生物学特征差异,其中长芒草有较高的功能性指标(比叶面积、叶片养分含量、比根长和比根面积),大针茅有较高的形态指标(植株高度、根冠比和根系形态),甘青针茅上述指标均为中等水平,但有较高的叶片干物质含量和分蘖数目。由于针茅生物量与其高度、根系长度呈正相关性,使得大针茅具有较高的生物量。(5)3种针茅生物量和根系形态指标在水分添加下平均分别增加94.91%和55.63%,对养分添加响应较小,演替早期土样接种使得3种针茅比根长和比根面积平均增加11.90%,演替中、后期土样接种使3种针茅生物量平均提高51.30%的同时使其根冠比平均下降22.72%。相比于单种生长模式,混种生长模式下3种针茅根系比根长和比根面积平均增加11.75%。此外,3种针茅对水肥的竞争能力表现为长芒草大针茅甘青针茅,且水肥添加对针茅竞争能力的影响依赖于土壤环境,表现为演替早期、中期和后期土壤中的水肥添加处理可分别提高长芒草、大针茅和甘青针茅的竞争能力。(6)3种针茅的植物-土壤反馈效应存在明显种间差异,体现在大针茅对同种植物产生显著正反馈作用,且其与禾草类植物互为正反馈作用;长芒草和甘青针茅则负反馈作用于同种植物,正反馈作用禾草类植物并受到禾草类植物的负反馈作用。3种针茅间的反馈关系表现为为长芒草显著正反馈作用大针茅并受到大针茅的负反馈作用,甘青针茅与长芒草、大针茅之间均互为正反馈作用。由此可见,3种针茅自身及与其他植物间的植物-土壤反馈效应格局的种间差异是草地封育演替中大针茅取代长芒草成为优势种的重要原因之一。
[Abstract]:Fencing is economical and effective grassland management measures, is widely used in the Loess Plateau, the degraded grassland restoration management process. Fencing excluding grazing, mowing disturbances such as impact on grassland ecosystem, the grassland degradation in the benign direction to carry out the natural recovery process, reflected in the enclosed grassland coverage, productivity the increase and soil structure, fertility and microbial activity improved, accompanied by changes in plant community structure adjustment and species diversity of plant and soil. As the grassland ecological system includes two parts, the feedback effect between the natural recovery process of vegetation of grassland is an important driving force in succession, which makes study on grassland vegetation succession in the process of long-term plant soil feedback mechanism has important theoretical value and practical significance. Because the Loess Plateau of Ningxia cloud Mountain steppe has had the obvious change of vegetation pattern in a 35 A enclosure in the succession process, this study has the phenomenon of the replacement of the dominant species of Stipa communities as the research object, combined with field and laboratory tests, the vegetation succession time series grass root characteristics, the decomposition characteristics of dominant species of Stipa litter, and the response characteristics of Stipa grandis the plant growth rule on soil biological and non biological characteristic changes of the plant soil feedback effect index were analyzed. The main results are as follows: (1) in the long grass vegetation succession process, grass root biomass and root morphology were increased by 49.65% and 94.80%, and with the increase of soil moisture and nutrient content. Root, grass species richness decreased 37.11%. grass root characteristics are quite different in the proportion of different functional groups and the response of education measures on the letter, as long letter Education makes a grass plant for grass root community ratio increased from 41.65% to 81.22%, the perennial rhizomatous grass root system index increased more than 10 times, and the larger the grass plant specific root length and specific root area characteristics and soil C, close N resources promotion; in contrast, non grass root proportion is declining and the rules and characteristics of root was mainly affected by soil P resources. (2) with the increase of grassland fencing and the succession (0,5,9,22 and 30 A), Stipa root biomass and root morphological characteristics increased 87.29% and 119.73% respectively, and the pattern of species composition changed significantly is the root of Stipa bungeana, the proportion by the enclosure early 77.12%, gradually reduced to 22 a grassland enclosure 13.42%, and disappeared in the fenced grassland 30A; Stipa grandis root proportion of self fertility early 22.88% increased gradually and in the letter With 22 a grassland reached 86.58%, after the rapid decline; Gansu appeared in enclosure 30 Stipa a grassland, and occupy the ratio of up to 77.22% dominant position. (3) a 2 a field experiment results show that the Stipa leaf and root litter in the decomposition of the average rate of mass loss at the end of 36.07% and 32% respectively, Stipa grandis leaf litter decomposition rate is the highest, root litter is the changes of the elements in Gansu is the fastest.3 species of Stipa decomposition litter decomposition process is similar, but affected by litter type, the leaf litter C content from an average of 452.24 g kg-1 reduced to 440.21 G - kg-1, root litter the C content of kg-1 increased from an average of 420.73 g to 435.09 G - kg-1; leaf and root litter N content fluctuation decline, the ratio of C/N increasing; the P content of leaf litter from an average of 0.29 g kg-1 increased to 0.58g, kg-1, root litter The P content is from an average of 0.30 G - kg-1 wave decreased to 0.26 g and kg-1. three species of Stipa leaf and root litter C, N and P elements were released and release mode, respectively in 23.78%-39.28%, between 37.20%-60.38% and 21.30%-52.28%. Correlation analysis showed that the litter decomposition rate and the initial N content positively and, with the initial C/N ratio was negative correlation. 3 (4) showed significant differences in plant species of Stipa bungeana and biological characteristics, functional index (higher specific leaf area, leaf nutrient content, specific root length and specific root area), S.grandis morphological index of high (plant height, root shoot ratio and the root morphology), Gansu Stipa were in medium level, but there is a higher number of leaf dry matter content and tillering. Because Stipa biomass and height, root length was positively correlated with the biomass of Stipa grandis had higher (5) 3. Stipa species biomass and root morphological indexes in water added average increased 94.91% and 55.63%, in response to nutrient addition in small, early successional soils inoculated with the 3 kinds of Stipa specific root length and specific root area increased by 11.90% on average, while the late succession, soil inoculation of 3 Stipa biomass increased 51.30% in average. The ratio of root was decreased by 22.72%. compared to the single species growth model, hybrid growth mode 3 Stipa root specific root length and specific root area increased 11.75%. in addition, the competition ability of 3 kinds of water and fertilizer for Stipa bungeana S.grandis Gansu and fertilizer effects on Stipa, Stipa competitive ability depends on the soil the environment is early middle and late succession, soil water and fertilizer added processing can improve the S.bungeana respectively, S.grandis Qinghai and Gansu Stipa competitive ability. (6) 3 species of Stipa plant soil feedback effect Significant interspecific differences, reflected in the S.grandis on the same plant species have a significant positive feedback effect, and the grasses and other positive feedback; S.bungeana and Gansu is a negative feedback effect on Stipa species of plants, the positive feedback of grasses and grasses of the negative feedback effect of.3 feedback the relationship between the performance of Stipa bungeana is significant positive feedback and negative feedback effect by stipagrandis stipagrandis, Gansu and Stipa bungeana, S.grandis between each other for positive feedback. Thus, interspecific differences in plant species of Stipa - 3 itself and other plant soil feedback effect pattern of grassland fencing in the succession of Stipa bungeana instead become one of the important reasons of the dominant species.

【学位授予单位】：西北农林科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S812
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本文编号：1658714