【作者】 李亚娟；

【导师】 龙瑞军；

【作者基本信息】 甘肃农业大学 ， 草业科学， 2013， 博士

【摘要】 高寒草地是青藏高原畜牧业发展的基础。土地利用是自然条件和人为活动的综合反映，土地利用变化对土壤养分含量有着重要影响，同时也影响着生态系统的结构和功能，以及物质循环和能量流动。由于畜牧业需求、草地退化和鼠害猖獗等因素，青藏高原土地利用格局正变得多样。为了解土地利用格局变化对青藏高原高寒草地的影响，于青海省门源县门源种马场、共和县塔拉滩、玛多县鄂陵湖管理站、曲麻莱县约改滩和安多县县城大滩，选择具有典型性和代表性原生草地、封育草地、退化草地、人工草地和农田等土地利用格局分层（0～10cm，10～20cm，20～40cm…）进行全剖面土壤样品采集，研究高寒草地对土地利用格局的响应机制。通过调查确定门源种马场高寒草地利用格局有原生矮嵩草草甸、原生灌丛草甸、退化矮嵩草草甸、退化灌丛草甸、人工草地和农田六种；塔拉滩有封育芨芨草草原、退化芨芨草草原、取土坑、农田、和人工草地草地五种；鄂陵湖管理站有双叉细柄茅原生草原、双叉细柄茅退化草原和人工草地三种；约改滩有原生高寒草甸草原、退化高寒草甸草原、退化高寒草原细柄茅和人工草地四种；安多有原生草甸草原和退化草甸草原两种。研究结果表明：1.青藏高原高寒草地退化导致地上部生物量显著降低，草地生产力下降，但退化使地下生物量普遍有增加的趋势；开垦为农田和人工草地虽然可以获得较高的地上生物量，但地下生物量却很少，这不利于草地的培育和恢复。2.退化使门源和塔拉滩表层土壤的容重明显升高，鄂陵湖管理站和约改滩由于土壤容重整体较大，退化对土壤容重并未产生明显影响。开垦由于翻耕的作用土壤容重有降低的趋势。3.退化导致高寒草地0-10cm土层土壤有机碳、全氮和全磷含量显著降低，但降低的程度因区域而有差异。门源有机碳、全氮和全磷含量平均降低了40.7%、36.0%和17.3%，开垦导致有机碳和全氮均损失了一半左右；塔拉滩退化导致有机碳含量降低了23.2%，而全氮和全磷的降低幅度不大，开垦也导致有机碳损失了一半左右；约改滩有机碳降低了52.9%；安多草地退化导致土壤有机碳、全氮和全磷含量均升高，分别升高了42.6%、104.5%和31.6%。4.退化导致门源和塔拉滩土壤有效氮和有效磷含量显著下降，这也是草地生产力下降的原因之一。由于施肥的作用，开垦种植使得表层土壤有效氮和有效磷含量均较高，但下层变化不大，这对于人工草地的可持续性的不利。退化和开垦均导致玛多鄂陵湖站和曲麻莱约改滩研究区域土壤表层的有效氮和有效磷含量有升高的趋势。5.安多草地土层很薄，土壤整体肥力水平极低，有机碳最高仅为5g/kg，全氮最高仅为0.45g/kg，全磷最高仅为4.4g/kg，有效氮最高仅为27mg/kg，有效磷最高仅为5mg/kg。6.研究区域中除门源研究区域外，土壤的全氮含量普遍偏低，大部分土壤的全氮含量都低于0.5g/kg，属于极度缺乏，研究区域自东北向西南土壤全氮含量逐渐降低。除门源县外，原生草地和退化草地土壤的全磷和全磷含量相对比较稳定，受利用格局的影响较小，全磷含量多在2～4g/kg，有效磷多在4～7mg/kg。7.塔拉滩的取土坑利用格局，由于取土过程拿走了上层土壤，现在的表层土壤是原来的下层土壤土壤碳氮磷的含量极低，是一种特殊的利用格局，恢复利用的难度较大，应持续加强营养元素的投入及整个土壤的培肥。8.青藏高原原生草地土壤碳氮磷沿土壤剖面自上而下普遍有明显的变异，而草地退化和开垦使土壤碳氮磷沿土壤剖面的变异消失或者减小。更多还原

【Abstract】 Alpine grassland is the foundation for animal husbandry development onQinghai-Tibet Plateau. Land use is the comprehensive reflection of the naturalconditions and human activities. The land use changes has an important influence onsoil nutrient content, also affect the ecosystem structure and function, as well as thematerial circulation and energy flow. Because of the husbandry needs, grasslanddegradation and rodent overruning, the land use pattern is becoming diversity onQinghai-Tibet plateau. Soil carbon nitrogen and phosphorus are the essential nutrientelements for plant growth, especially grassland plants. The study was to find theeffects of land use changes on soil carbon nitrogen and phosphorus on Qinghai-TibetPlateau, and the typical and representative land use pattern five area on Qinghai-TibetPlateau were selected. The five area were Menyuan county, Tara beach in Gonghecounty, Maduo county, Qumalai county of Qinghai Province and Anduo county inTibet. The land use pattern included native grassland, enclosed meadow, degradedgrassland, artificial grassland and farmland. Soil land sample were collected by thesoil layer(0～10cm,10～20cm,20～40cm...) in every sample grassland in every landuse pattern.The investigation showed that there were six land use patterns in Menyuancounty, the native Kobresia humilis meadow, native shrub meadow, degradedKobresia humilis meadow, degraded shrub meadow, artificial grassland and farmlandrespectively, five in Tara beach, enclosed Achnatherum splendens grassland,degraded Achnatherum splendens grassland, excavating pit, farmland and artificialgrassland, three in Maduo county, native Ptilagrostis diehotoma grassland, degradedPtilagrostis diehotoma grassland and artificial grassland, four in Qumalai County,native alpine meadow, native alpine grassland, degraded alpine grasslands andartificial grassland, and two in Anduo county, native meadow steppe and degradedmeadow steppe. The result showed that:Degradation of alpine grassland on Qinghai-Tibet Plateau resulted in theaboveground biomass significantly reduced and the grassland productivity declined,but the underground biomass showed increased trend. Reclamation for farmland andartificial grassland obtained higher aboveground biomass even than native grassland,but the underground biomass was small, which was not benificial to the cultivationand restoration of the grassland. Degradation made soil bulk density of the surface soil increased, whilereclamation decreased the surface soil bulk density because of tillage in Menyuan andGonghe county. Soil bulk density was wholely higher in Maduo and Qumalai studyareas, and degradation showed no significant effects on soil bulk density. Butreclamation resulted in soil bulk density of the surface soil decreased because of thecultivation.Soil organic carbon, total nitrogen and total phosphorus in0～10cm soil layerwere significant decreased because of the alpine grassland degradation, and there wasregional difference in the reduction. Soil organic carbon, total nitrogen and totalphosphorus reduced by an average of40.7%,36.0%and17.3%respectively, andreclamation led to the loss of organic carbon and nitrogen in about half in Menyuancounty. Soil organic carbon reduced by an average of23.2%, and total nitrogen andtotal phosphorus decreased little in Gonghe county. Reclamation had also led to theloss of organic carbon by about half. Soil organic carbon decreased52.9%in Qumalaicounty. Soil organic carbon of the artificial grassland in0～10cm is higher than175%of the native grassland. Soil organic carbon, total nitrogen and total phosphoruscontent has increased under degradation in Anduo county, and were increased by42.6%,104.5%and31.6%respectively.Degradation made soil available nitrogen and available phosphorus contentsignificantly decreased in the two research areas, Menyuan and Gonghe County by theQilian Mountain, which could be one of the reasons for the grassland productivitydecrease. Planting cultivation made soil available nitrogen and available phosphoruscontent in the surface soil higher due to the role of fertilization due to the role offertilization, but had no significant effects on the deeper soil layors, which was not infavor of the sustainable use of the reclaimed grassland and the management ofdegraded grassland restoration. Degradation and reclamation showed incredsedeffectc on soil available nitrogen and available phosphorus in surface soil in Maduoand Qumalai research areas of the Source Region of Three Rivers.Reclamation use pattern in Anduo area was less. Soil generally fertility level wasvery low in this region, the highest organic carbon only5g/kg, the highest totalnitrogen only0.45g/kg, the highest total phosphorus only4.4g/kg, the highestavailable nitrogen only27mg/kg, and phosphorus only up to5mg/kg.In the study areas, except for Menyuan area, soil total nitrogen content was generally low, soil total nitrogen content was lower than0.5g/kg in most, whichmeaned extreme shortage. Soil total nitrogen content was gradually decreaed fromnortheast to southwest in the study areas. Except for Menyuan county, soilphosphorus content of the native grassland and degraded grassland was relativelystable, available phosphorus content was generally low, and the spatial variability oftotal phosphorus and available phosphorus content was slight. The total phosphoruscontent variated from2g/kg to4g/kg, and available phosphorus conten from4to7mg/kg, which showed that the degradation has little effect on soil phosphorus.Grassland restoration and utilization needs phosphorus inputs.The excavating pit pattern in Taratan showed extremely lack of soil carbonnitrogen and phosphorus content,which is mainly because the topsoil in the area weretaken away and the current topsoil was the deeper soil formerly. Therefor, soilnutrient contents were extremely lack. Nitrogen and phosphorus input and total soilfertility increase should be strengthened in grassland recovery and utilization.Grassland degradation and reclaimed made soil nutrients variation along soilprofile disappeared or reduced. Soil carbon nitrogen and phosphorus in nativegrassland showed significant variation along soil profile, while that in artificialgrassland and farmland was not significant variation. Grassland degradation andreclaimed made grassland developed to the direction of farmland. Grasslanddegradation showed great loss effects on soil organic carbon, total nitrogen and totalphosphorus in surface soil, while have little effect on that in10～20cm soil, which isbecause degradation inproved soil organic carbon mineralization in surface soil,leading to the carbon oxidation loss.更多还原