【作者】 李媛；

【导师】 程积民；

【作者基本信息】 西北农林科技大学 ， 草业科学， 2012， 硕士

【摘要】 云雾山典型草原位于黄土高原地区，该地区由于降水量低，且多以暴雨出现，水土流失与干旱并存，植被恢复难度较大。以往学者对该区施行的植被恢复措施主要有人工建设和禁牧封育，并且取得了显著效果。但近年来由于封育时间过长，一些草地开始出现退化现象，植被的覆盖度减小。出现这种现象，主要由于长期的封育，缺乏适度的干扰，最终导致草地生态系统枯落物的大量积累，物种多样性减小。“中度干扰假说”指出只有当干扰频率中等时，物种生存的机会才是最多的，群落多样性最高。因此，本研究主要从火烧干扰对草地植被特征及土壤理化性质的影响展开研究，旨在为黄土高原典型草原的可持续发展提供基础数据。由于人为原因着火，本试验选择3个本氏针茅群落分别为火烧第1年（2011年5月过火）、火烧第3年（2009年11月过火）、火烧第11年（2000年5月过火），同时选择邻近的一块未烧地作为对照。于2011年9月对4个样地进行植被调查及土壤养分测定，以期揭示不同火烧恢复年限植被及土壤特征。研究结论如下：对不同火烧恢复年限本氏针茅群落植被特征进行研究，结果表明：1、火烧第1年、3年、11年和未烧样地物种数分别为37种、35种、38种和33种，可见火烧样地物种数增加。过火后，第1年和第3年两个样地本氏针茅的优势度小于大针茅，说明优势种——本氏针茅对火烧很敏感，经火烧干扰后物种优势度减小。火烧第11年，本氏针茅优势度已恢复，增加到85.85，而未烧地本氏针茅的优势度为72.01，说明火烧对本氏针茅生长具有潜在作用。2、不同火烧恢复年限本氏针茅群落密度、高度、盖度、地上生物量及枯落物蓄积量的变化。火烧初期即3年以内，群落的高度、地上生物量和枯落物蓄积量显著减小，密度显著增加；火烧后期即11年时，群落的密度（株丛数）显著减小，主要由于优势种本氏针茅属多年生禾本科植被、簇生,并且在群落中占有优势地位；但火烧第11年时群落盖度、生物量和枯落物蓄积量显著增加，高度无显著变化。火烧第1年对地上生物量无显著影响，但可显著减小枯落物蓄积量。3、不同火烧恢复年限群落多样性的变化。火烧第1年、3年、11年与未烧地比较，群落多样性指数无显著差异；火烧第1年均匀度指数显著减小，但丰富度指数显著增加；火烧第3年、11年与未烧地相比，均匀度指数和丰富度指数均无显著差异。对不同火烧恢复年限本氏针茅群落土壤理化性质进行研究，结果表明：1、火烧对土壤含水量的影响表现为：火烧第1年含水量变化最大，土壤表层0-10cm含水量大于未烧地，10cm以下土壤含水量逐渐减小。火烧第3年、11年和未烧地土壤含水量变化趋势基本一致。2、火烧对土壤容重的影响表现为：0-50cm土壤剖面从上到下，火烧第1年土壤容重变化幅度最小；火烧第3年土壤容重变化最大；火烧第11年和未烧地容重变化基本一致。土壤0-20cm，火烧第1年、3年容重小于未烧地和火烧第11年；土壤20-40cm，火烧第1年容重小于未烧地和火烧第11年，火烧第3年大于未烧地和火烧第11年；土壤40-50cm，除了火烧第1年容重最小，其他样地容重基本一致。3、火烧后土壤化学性质的变化。火烧第1年地土壤剖面各层SOC、全N、全P和速效K含量都显著高于未烧地；火烧第3年样地土壤剖面各层SOC、全N、全P和速效K含量与未烧地差异不显著；火烧第11年样地土壤剖面各层全N含量都显著高于未烧地，SOC、全P和速效K含量除了0-10cm层与未烧地差异不显著外，其它土层均显著增加；4个样地的土壤剖面各层从上到下SOC、土壤全N、全P和速效K含量呈递减趋势；3个火烧样地土壤表层（0-10cm）的pH值和未烧地差异不显著。更多还原

【Abstract】 The Yunwu Mountains locate in typical steppe of loess plateau, due to less rainfall, soil andwater loss and drought, the restoration of vegetation is difficult. Artificial grasslandconstruction and pasture enclosure were conducted as restoration measures of this region byprevious researchers, and had achieved many positive effects. However, in recent years,because of long-term enclosure and lack of appropriate interference, grassland appeared somedegeneration phenomenon, and causing the coverage of vegetation decreasing, many littersaccumulating."Moderate interference hypothesis" points out that only when the interferenceof medium frequency, the species had the most the chance of survival, species diversity wasthe highest. In this paper, we mainly focus on the effect of fire on the vegetation and soilnutrient characteristics.In present studies, three Stipa bungeana communities were selected as experimentalsamples that burned in2011(one year),2009(three years) and2000(eleven years),respectively, and the nearby sample without burned as control. In September2011, thevegetation characteristics and soil nutrient were determined. The aim of this study was toreveal the characteristics of vegetation and soil physical and chemical properties in differentburning periods. The resuts were as follow:Vegetation character of Stipa bungeana communities:(1) The number of species were37(burned one year)、35(burned three years)、38(burnedeleven years) and33(without burned), respectively. The number of species increased inburning sample. After fire, the advantage degree of S. bungeana were less than the advantagedegree of Stipa grandis in burned one year and three years, which explained that the dominantspecies S. bungeana was sensitive for fire experiment. The advantage degree of S. bungeanahad been restored in burned eleven years, which explained that fire had a positive effect onthe S. bungeana community in long-term development.(2) Changes of community density, height, coverage, above-ground biomass and theamount of litter. For burned three years, the height of the community reduced, density andabove-ground biomass increased, coverage had no significant change; For burned eleven years, the density and coverage of the community reduced, the above-ground biomassincreased, the height of the community had no significant change. The main reasons were thatthe S. bungeana was perennial grasses, tufted and inhibited the growth of other forbs. Forburned one year, fire had no significant effect on above-ground biomass, and reduced amountof litter significantly.(3) Changes of community diversity. Compare with without burned sample, the diversityindex had no significant change for burned samples.The evenness index decreasedsignificantly in burned one year, and compare with without burned sample, evenness indexhas no significant difference for burned three and eleven years. The abundance index wasincreased in burned one and three years, and the fire had no significant difference for burnedeleven years.Soil physical and chemical properties of S. bungeana community:(1) Affect of fire on soil moisture: The content of soil moisture changed significantly inburned one year, in the surface soil layer0-10cm water content were greater than withoutburned sample,10cm below the soil water content decreased gradually. Three years andeleven years after the fire, the soil moisture had no significant difference with unburningstand.(2) Affect of fire on soil bulk density was as follows: The soil bulk density changedsignificantly in burned three years, compare with witnout burned sample,0-20cm of soilbulk density was less,20-40cm was greater,40-50cm was same. For burned eleven years,soil layers of bulk density were basically same with without burned.(3) Change of soil chemical properties after fire was as follows: SOC, total N, total P andavailable K concentrations were significantly higher at all depths for burned samples thanwithout burned sample. SOC, total N, total P and available K concentrations had nosignificant differences at all depths in burned three years. Total N concentrations weresignificantly high at all depths in burned eleven years. SOC,total P and available Kconcentrations were significantly high at all depths(except0-10cm).For four samples, SOC,total N, total P and available K concentrations were decreasing in soil profile from up to down.Soil pH had no significant differences in burned three years.更多还原