【作者】 蔡志风；

【导师】 郝明德；

【作者基本信息】 西北农林科技大学 ， 生态学， 2011， 硕士

【摘要】 本文利用长期轮作培肥定位试验,并结合2010年对黄土区不同种植年限苜蓿草地的野外调查,对连作不同施肥条件、粮草轮作不同生长年限以及黄土区不同种植年限的苜蓿草地群落特征、多样性及其稳定性变化进行了研究,为黄土区苜蓿人工草地持续高效利用提供科学的依据。主要研究结论如下:1.不同施肥条件下连作苜蓿草地群落物种多样性和生态优势度指数变化不显著,植被生物量明显增大,苜蓿种群重要值及其产量亦显著增加,施肥可维系群落多样性和稳定性,提高苜蓿草地生产力。2.施肥后,苜蓿生态位宽度增大,竞争力相对增强;杂类草之间生态位重叠较大且竞争较为激烈,苜蓿和杂类草的竞争相对缓和,施肥可增强苜蓿种群竞争力,缓解种间竞争压力,提高群落的稳定性。不同施肥措施下连作苜蓿草群落物种多样性与生产力的关系发生了一些改变,总体上表现为负二次函数关系。3.轮作苜蓿草地植被生物量、群落物种多样性和生态优势度指数,苜蓿重要值及其产量随生长年限增加均呈先升后降的变化趋势,物种丰富度指数、杂类草生物量的变化趋势与之相反。人工草地3龄后,随着苜蓿生长时间延长和杂类草入侵,群落生产力稳定性开始显著下降,人工草地呈明显退化态势。4.轮作苜蓿草地群落物种多样性与生产力关系随种植年限的延长发生了一些改变,这与种间竞争密切相关。轮作草地中苜蓿生态幅(0.60)最宽,附地菜(0.58)等杂类草也具有较宽生态幅,苜蓿与附地菜的重叠值(0.995)最大,且同其它杂类草的重叠程度亦较高,杂类草与苜蓿间竞争激烈,导致草地退化。5.轮作苜蓿草地群落稳定性在3龄时最大,尔后随草地生产力和生物多样性下降而降低,人工草地很快衰退,苜蓿施肥可适当延缓人工草地的自然演替进程。6.苜蓿人工草地大约在26年后,其群落开始向长芒草过渡,逐渐被长芒草群落所替代,标志着苜蓿人工草地已经退化。草地演替6龄后,群落物种多样性呈明显增加趋势,群落结构趋向于越复杂化,其生态稳定性相对增大,苜蓿人工草地处于退化演替阶段。7.苜蓿人工草地群落物种多样性与生产力的关系随演替进程推进发生了一些变化,它们在不同演替时间和生境条件下的总体关系表现为负二次函数关系。人工草地中苜蓿和杂草附地菜间重叠值最大为0.99,竞争最激烈。杂类草与苜蓿之间具有高度重叠生态幅是导致草地退化的一个重要因素。更多还原

【Abstract】 The changes of the communities characteristics,biodiversity and stability of alfalfa grasslands communities under different fertilizations,different growth age alfalfa grasslands communities in cropping wheat-alfalfa rotation system from the trial of long-term located fertilize.and the investigation of different growth age alfalfa grassland in gully region of the Loess Plateau were analyzed,respectively,to provide the scientific basis for sustainable and efficient use of artificial alfalfa grassland in Loess Region.The results were as follows:1.The species diversity indexes and ecological dominance index of the continuous cropping alfalfa grassland under different fertilizer treatments did not significantly differ,but the vegetation biomass tended to obviously increase,and the yield and importance value of alfalfa populations also raised significantly.Pmanure could maintain species diversity and stability of communities to some extent,and enhance alfalfa grassland productivity.2.After fertilizer treatments,niche breadth of alfalfa population increased and the competitiveness relatively strengthened;niche overlaps and competitives between two forbs were the larger and more intense,while the competitives.between Medicago sativa and other species were relative ease.fertilization can enhance the competitive of alfalfa populations, reduced the pressure between two species and improve the stability of communities.Under different fertilizations,the relationship between species diversity and productivity in the continuous cropping alfalfa grassland had been some changes, generally showed a negative quadratic function.3.The vegetation biomass,species diversity and ecological dominance index of the alfalfa rotation grassland,and the important value and yeild of alfalfa populations with the growth years decreased at first and increased subsquently decreased,but the species richness index and the aboveground biomass of forbs were opposite trends.After artificial grassland 3 years old,the stability of community productivity began to decline significantly,artificial glassland was in significantly degraded situation with the growth years of alfalfa and forbs prolonged invasion.4.The relationship between species diversity and productivity in alfalfa rotation grassland had undergone some changes with the plant years extension,which is closely related to interspecific competition.In rotation glassland the ecological amplitude (0.60)of alfalfa populations was the most wide,and the ecological amplitude of forbs such as Peduncularis(0.58) were larger , alfalfa and Peduncularis attached to the overlap value(0.995).maximum,and with other forbs also higher degree of overlap,the competitions between Medicago sativa and fors were most intense,which led to the sowing grassland degrade.5.The stability of alfalfa grassland in rotation was best in 3 years old,and later reduced with the decline in grassland productivity and biological diversity,grassland artificial would soon degrade,fertilization may be appropriate to delay the process of natural succession of artificial glassland.6.Artificial alfalfa grassland communities began to evolved toward the original vegetation community after about 26 years,was gradually replaced by bungeana community,which marked the alfalfa pasture has been completely degraded.After age 6 of grassland succession,the species diversity increased significantly,the structure of communities tended to be more complex,and its ecological stability relatively increased,showing that the artificial alfalfa grassland was in a stage of regressive succession.7.The relationship between species diversity and productivity had undergone some changes in alfalfa artificial grassland with the succession process forward,the overall relationship between them was a negative quadratic function under different under different successional time and habitat conditions.Maximum overlap occured between alfalfa and Peduncularis,its value was 0.99,there were the most competitive among alfalfa and forbs.The competitions between forbs and alfalfa for a limited resource is an important factor,which made the sowing grassland more degenerative.更多还原