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1、青海大学硕士学位论文土地利用方式和植被退化对青海湖北岸高寒草原土壤碳氮含量 的影响姓名：王振群申请学位级别：硕士专业：草业科学指导教师：乔有明20090401I 摘 要 采用野外采样与室内分析测定相结合的方法，以位于青海湖北岸的青海省三角城种羊场为研究区域， 通过对不同土地利用方式、 退化程度和植被类型的样地进行植物和土壤样品的采集和分析，从植被和土壤两个方面对不同样地植物群落数量特征、生物量、土壤颗粒组分、土壤有机碳和全氮含量分别进行了比较研究，结果如下： 1选取围栏封育、围栏放牧、多年生人工草地和农田 4 种土地利用方式为研究对象。显著性分析表明不同土地利用方式间土壤有机碳、全氮储量产生了
2、较明显的差异。030cm深度土体单位面积有机碳储量由高到低依次为： 多年生人工草地围栏封育草地围栏放牧草地农田，多年生人工草地显著高于农田（P0.05） ，而另外两个利用方式下，土壤有机碳储量差异不显著（P0.05） ；030cm 深度全氮储量与有机碳储量变化趋势相似。4 种土地利用方式相比较， 地上生物量由高到低表现为农田多年生人工草地围栏封育草地围栏放牧草地，其值分别为：478.13 g/m2、221.94 g/m2、180.46 g/m2和 115.03 g/m2，其中农田的地上生物量与其它 3 个样地间差异显著（P0.05） ，而其它 3 种土地利用方式间差异不显著（P0.05） ；0
3、30cm 土体内地下生物量由高到低依次为围栏封育围栏放牧多年生人工草地农田，分别为 2416.67 g/m2、1688.25 g/m2、1224.50 g/m2和 1290.75 g/m2。010cm土层土壤粘粒含量以多年生人工草地最高，并显著高于其它 3 种土地利用方式（P0.05） ；1020cm 土层土壤粘粒含量由大到小依次为：多年生人工草地农田围栏封育草地围栏放牧草地；2030cm 土层的土壤粘粒含量无显著差异。同一土层各土地利用方式间粉粒含量均差异不显著（P0.05） 。 2选择了轻度、中度和重度 3 种退化梯度。随着退化程度的加剧，植物群落物种丰富度、 植被盖度、 多样性指数和均匀
4、度指数均呈减小的趋势； 地上和地下生物量亦呈下降趋势。植被发生退化的同时，土壤基本理化性质也产生了差异。随着退化程度的加剧，土壤含水量逐渐减小，土壤 pH 和土壤容重呈增加趋势，土壤砂粒含量逐渐增加，而粘粒含量减少。不同退化程度下， 030 深度单位面积有机碳储量由高到低表现为轻度退化草地中度退化草地重度退化草地，其值分别为 7.18 kg/m2、5.85 kg/m2和 5.20 kg/m2，轻度退化草地显著高于重度退化草地（P0.05） ，与轻度退化草地相比，中度和重度退化草地土壤有机碳储量分别减少了 18.52%、27.58%；土壤全氮储量与有机碳储量变化趋势类似。 3选取了芨芨草草地、金
5、露梅灌丛和冷地早熟禾草地 3 种植被类型。3 种不同植被类型样地相比较，地上生物量从高到低表现为：金露梅灌丛芨芨草草地冷地早熟禾草地，II 其值分别为 326.75 g/m2、211.23 g/m2和 115.03 g/m2，其中芨芨草草地和冷地早熟禾草地之间差异不显著（P0.05） ，但都显著低于金露梅灌丛（P0.05） ；030cm 土体总地下生物量从高到低亦表现为金露梅灌丛芨芨草草地冷地早熟禾草地， 其值分别为4933.58 g/m2、2744.58 g/m2和 1688.25 g/m2，其中金露梅灌丛与其它两种植被类型间差异显著（P0.05） 。所测样地土壤均呈偏碱性，芨芨草草地土壤
6、pH 依土层从上至下逐渐减小，变化规律与其它2 种植被类型相反；土壤含水量介于 13.94%56.10%之间，3 种植被类型 030cm 土层平均土壤含水量以金露梅灌丛最高， 芨芨草草地土壤含水量从上层至下层表现为逐渐增加的变化规律， 与另外两个样地变化趋势相反； 不同植被类型下土壤容重的垂直变化规律均不相同。30 深度单位面积土壤有机碳和全氮储量从高到低均表现为：金露梅灌丛芨芨草草地冷地早熟禾草地， 其值分别为 12.12 kg/m2、 7.83 kg/m2、 5.87 kg/m2和 1.11 kg/m2、 0.93 kg/m2、0.62 kg/m2，金露梅灌丛与芨芨草草地、冷地早熟禾草地间
7、差异显著（P0.05） 。 关键词：关键词：青海湖；土地利用方式；草地退化；植被类型；土壤有机碳；土壤全氮 III Abstract The study area was located in the Sanjiao Cheng Sheep Breeding Farm, which is in the northern region of the Qinghai Lake. Different land-use types, degradation degrees and vegetation types were selected to get soil and plant samples.
8、 On the basis of field investigation and laboratorial analysis, the quantitative characteristics of community, aboveground and underground biomass, soil particle size, the content of soil organic carbon and total nitrogen were investigated. The main results of the study are shown as follows: 1 Four
9、different land-use types, fenced and ungrazed （FU） , fenced and seasonal grazed （FG） , perennial pasture（PP）and crop land（CL） were selected in this study. The results showed that soil organic carbon and total nitrogen storage were different under different land-use types. The storage of soil organic
10、 carbon per unit area varied in the order of PPFUFGCL. The soil organic carbon in the perennial pasture was significantly higher than that in crop land (P0.05), and no significant difference was found between the other two types(P0.05). The change of total nitrogen was similar to organic carbon. The
11、 aboveground biomass varied in the order of CLPPFUFG, and the aboveground biomass of the crop land was siginificantly higher than the orther sites,No significant differences were found among the other three types(P0.05). In 030cm soil depth, the underground biomass varied in the order of FUFGPPCL, t
12、heir values were 2416.67g/m2, 1688.25g/m2, 1224.50g/m2 and 1290.75g/m2 respectively. In 010cm soil layer the soil clay content of PP was significantly higher than those of other three types (P0.05); the soil clay content of the 1020cm soil layer ranged with an order of PPCLFUFG; no significant diffe
13、rence of soil clay content was found in 2030cm soil layer under different land-use types. The soil silt content of the four different land-use types had no significant differences in the same soil layer (P0.05). 2Three degradation degrees, lightly degraded（LD）, moderately degraded（MD） and severely d
14、egraded（SD） were selected in this study. The results showed that with the increase of degradation degree, the species richness index, vegetation coverage, diversity index and evenness index were all correspondingly shown to decrease, and both aboveground and underground biomass also showed decreasin
15、g tendency. Soil physical-chemical properties were different from each other under different degradation degrees when the vegetation showed degradation. The IV increasing degradation degree led to a decrease of soil water content and an increase of soil bulk density and soil pH, and the soil sand co
16、ntent showed an increasing tendency while the soil clay content decreased with the increasing degradation degrees. The storage of soil organic carbon per unit area varied in the order of LDMDSD and their values were 7.18kg/m2, 5.85kg/m2 and 5.20kg/m2. The soil organic carbon in the lightly degraded grassland was significantly higher than that in the severely degraded grassland(P0.05). Compared with the lightly degraded gra
