本文選題：封育　切入點：植被演替　出處：《西北農(nóng)林科技大學(xué)》2017年博士論文

【摘要】：圍欄封育是草原經(jīng)濟有效的管理措施,被廣泛應(yīng)用于黃土高原退化草地的恢復(fù)管理過程中。封育排除了放牧、刈割等人為干擾對草地生態(tài)系統(tǒng)的影響,使得退化草地開展朝良性方向的自然恢復(fù)進(jìn)程,體現(xiàn)在封育后草地蓋度、生產(chǎn)力的增加和土壤結(jié)構(gòu)、肥力和微生物活動的改善與提高,同時伴隨植物群落結(jié)構(gòu)的調(diào)整和物種多樣性的變化。植物和土壤作為草地生態(tài)系統(tǒng)的兩大主要組成部分,兩者間的反饋作用是草地自然恢復(fù)進(jìn)程中植被群落演替的重要驅(qū)動力,這使得針對草地長期封育演替進(jìn)程中的植物-土壤反饋機制的研究具有重要的理論價值和實踐意義。因為黃土高原地區(qū)寧夏云霧山典型草原在長達(dá)35 a的封育演替進(jìn)程中已發(fā)生明顯植被格局變化,本試驗選取具有優(yōu)勢種更替現(xiàn)象的針茅群落作為研究對象,結(jié)合野外和室內(nèi)試驗,對封育演替時間序列草地根系特征、優(yōu)勢種針茅凋落物分解特性、針茅植物生長規(guī)律對土壤生物和非生物特性變化的響應(yīng)特征及針茅的植物-土壤反饋效應(yīng)指數(shù)進(jìn)行了分析。主要研究結(jié)果如下:(1)在草地長期封育演替進(jìn)程中,草地根系生物量和根系形態(tài)特征分別增加49.65%和94.80%,并伴隨土壤水分和養(yǎng)分含量的增加,草地根系物種豐富度下降37.11%。草地根系特征在不同功能組的分配比例及其對封育措施的響應(yīng)存在較大差異,表現(xiàn)為長期封育使得禾草類植物所占草地根系群落比例由41.65%升高至81.22%,其中多年生根莖型禾草根系指標(biāo)增加幅度達(dá)10倍以上,這與禾草類植物根系較大的比根長和比根面積特征及其所受土壤C、N資源的促進(jìn)作用密不可分;相比之下,非禾草類植物根系所占比例呈不斷下降規(guī)律,且其根系特征主要受土壤P資源影響。(2)隨著草地封育演替年限的增加(0、5、9、22和30 a),針茅根系生物量和根系形態(tài)特征分別增加87.29%和119.73%,且其物種組成格局發(fā)生明顯變化,表現(xiàn)為長芒草根系比例由封育初期的77.12%,逐漸降至封育22 a草地的13.42%,并消失于封育30a草地;大針茅根系比例自封育初期的22.88%逐漸增加并在封育22 a草地達(dá)到86.58%,之后迅速下降;甘青針茅出現(xiàn)于封育30 a草地,并占據(jù)高達(dá)77.22%比例的優(yōu)勢地位。(3)為期2 a野外分解試驗結(jié)果顯示,針茅葉片和根系凋落物在分解末期的質(zhì)量損失率平均分別為36.07%和32.00%,葉片凋落物中大針茅分解速率最高,根系凋落物中則為甘青針茅分解最快。3種針茅凋落物分解過程中元素變化規(guī)律相似,但受凋落物類型影響,其中葉片凋落物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含量則平均由420.73 g·kg-1升高至435.09 g·kg-1;葉片和根系凋落物N含量波動式下降,使得其C/N比值波動式上升;葉片凋落物P含量平均由0.29 g·kg-1升高至0.58g·kg-1,根系凋落物P含量則平均由0.30 g·kg-1波動式下降至0.26 g·kg-1。三種針茅的葉片和根系凋落物C、N和P元素均呈釋放模式,且釋放比例分別在23.78%-39.28%、37.20%-60.38%和21.30%-52.28%之間。相關(guān)分析表明,凋落物分解速率與其初始N含量呈正相關(guān),并與初始C/N比值為負(fù)相關(guān)。(4)3種針茅表現(xiàn)出明顯植物生物學(xué)特征差異,其中長芒草有較高的功能性指標(biāo)(比葉面積、葉片養(yǎng)分含量、比根長和比根面積),大針茅有較高的形態(tài)指標(biāo)(植株高度、根冠比和根系形態(tài)),甘青針茅上述指標(biāo)均為中等水平,但有較高的葉片干物質(zhì)含量和分蘗數(shù)目。由于針茅生物量與其高度、根系長度呈正相關(guān)性,使得大針茅具有較高的生物量。(5)3種針茅生物量和根系形態(tài)指標(biāo)在水分添加下平均分別增加94.91%和55.63%,對養(yǎng)分添加響應(yīng)較小,演替早期土樣接種使得3種針茅比根長和比根面積平均增加11.90%,演替中、后期土樣接種使3種針茅生物量平均提高51.30%的同時使其根冠比平均下降22.72%。相比于單種生長模式,混種生長模式下3種針茅根系比根長和比根面積平均增加11.75%。此外,3種針茅對水肥的競爭能力表現(xiàn)為長芒草大針茅甘青針茅,且水肥添加對針茅競爭能力的影響依賴于土壤環(huán)境,表現(xiàn)為演替早期、中期和后期土壤中的水肥添加處理可分別提高長芒草、大針茅和甘青針茅的競爭能力。(6)3種針茅的植物-土壤反饋效應(yīng)存在明顯種間差異,體現(xiàn)在大針茅對同種植物產(chǎn)生顯著正反饋作用,且其與禾草類植物互為正反饋作用;長芒草和甘青針茅則負(fù)反饋作用于同種植物,正反饋作用禾草類植物并受到禾草類植物的負(fù)反饋作用。3種針茅間的反饋關(guān)系表現(xiàn)為為長芒草顯著正反饋作用大針茅并受到大針茅的負(fù)反饋作用,甘青針茅與長芒草、大針茅之間均互為正反饋作用。由此可見,3種針茅自身及與其他植物間的植物-土壤反饋效應(yīng)格局的種間差異是草地封育演替中大針茅取代長芒草成為優(yōu)勢種的重要原因之一。
[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.

【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：S812
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本文編號：1658714