【作者】 汪卫卫；

【导师】 胡良军；

【作者基本信息】 东北师范大学 ， 草业科学， 2007， 硕士

【摘要】 土壤是一个时空连续的变异体,具有高度的空间异质性。土壤空间格局就是这种空间异质性的具体表现。放牧的实质是一种生态干扰,干扰是引起生态系统空间异质性的重要来源之一。探索草地土壤养分空间格局在放牧干扰条件下的特征及其动态变化机制,对于认识放牧强度与草地土壤养分空间格局之间的关系有重要理论意义,并对揭示放牧与土壤养分之间复杂的生态关系具有重要作用。本研究采用野外随机典型样地调查与实验室分析的方法,同时利用传统统计学和地统计学相结合的数据分析与处理方法,对松嫩草地不同放牧压力下的土壤养分空间格局特征及其变化进行了研究,尤其针对草地土壤养分含量水平、空间变异性、空间自相关性及不同养分之间的相关性进行了系统的研究。利用地统计学的变异函数分析和Kriging空间插值估计法,比较不同放牧强度干扰对土壤各养分因子空间格局的影响。研究获得的主要结论如下:1、研究区6种土壤养分的变异系数在7.6%～29.1%之间。其中,土壤速效磷的变异系数最高,速效氮的变异系数最小。土壤有机质、全氮、全磷、速效磷的变异属于中等变异,而速效氮、速效钾的空间变异属于弱变异。各土壤特性的相关分析表明,土壤有机质与全氮、全磷和速效磷的相关系数较高,且与全磷呈极显著正相关,与速效磷呈显著正相关。2、天然无牧草地上,土壤中各种养分在剖面的分布基本为上高下低。土壤有机质、全氮、全磷含量随土层深度的增加逐渐下降;速效氮在0～50㎝土层,速效磷在0～100㎝土层呈先减少后增加再减少的“S”型分布;土壤养分在垂直方向上具有明显的分层和富聚现象。3、重度放牧导致土壤有机质在0～10㎝的含量下降,而轻度和中度放牧则增加了土壤有机质含量;土壤全氮在0～10㎝随放牧强度的增加而下降;土壤全磷在10～50㎝范围内以重度放牧含量最高,而在0～10㎝层则以中牧草地含量最高。土壤有机质、全氮和全磷三者之间具有相似的空间分布规律。4、土壤速效氮在各放牧区的含量均高于无牧区,且各放牧梯度下,速效氮含量在剖面的变化幅度不大;土壤速效磷含量(0～10㎝)随放牧强度的增加而增加,但10～20㎝重牧草地土壤中速效磷含量却陡然下降;土壤速效钾含量0～20㎝层,重牧草地高于其它样地,而20～30㎝、30～50㎝层以无牧草地土壤中速效钾含量最高。5、土壤有机质、全磷、速效磷的理论模型属于指数模型;全氮、速效氮、速效钾的理论模型属于球状模型;6种土壤养分中,有机质、全氮和全磷具有中等强度的空间相关性;而速效氮、速效磷和速效钾的空间相关性很弱。更多还原

【Abstract】 Soil is a continuum with high spatio-temporal heterogeneity which might be defined as spatial patterns as well. Ecological disturbance is one of the most important causes forming the spatial heterogeneity. Therefore, it is important to establish the dynamics of soil nutrients spatial patterns under grazing disturbance in grassland ecosystems; and it is also meaningful theoretically for recognizing the relations between grazing pressures and soil spatial heterogeneity; else, it is also helpful to further understand the interactions between grazing and soil nutrients patterns in grasslands ecosystem.Our research was conducted focusing on the grassland soil nutrients’spatial patterns under different grazing pressures on the Songnen meadow steppes. By use of site investigation and laboratory analysis, soil nutrients’contents, spatial variability, and correlation of different nutrient components under diverse grazing gradients were studied with the aid of statistic and geo-statistical methods. Data analysis was applied due to the semivariogram method and Kriging algorithm. Soil nutrients’spatial patterns under different grazing pressures were quantified and compared mutually. Herein, the grazing gradients were defined as naturally ungrazed meadows, lightly grazed meadows, moderately grazed meadows, and heavily grazed meadows. The soil nutrient indicators were selected as SOM, soil total nitrogen, total phosphorus, total potassium and soil available nitrogen, available phosphorus, and available potassium.Finally, some conclusions were established as follows:1.The coefficients of variability (CV) of all the target nutrients indicators appear all in the range of 7.6～29.1%, in which the CV of available phosphorus is the biggest while that of available nitrogen is at the down end. Soil organic matter (SOM), total nitrogen, available phosphorus perform with medium variance, while that of total phosphorus, available nitrogen, available potassium do with weak variance. The correlation analysis of each soil nutrient components shows that, the SOM performs extremely significantly positive with total phosphorus and significantly positive with available phosphorus.2.In natural grasslands, soil nutrients concentrate in the upper layer of the profile and decrease along the profile from top to lower. The distributions of SOM, total nitrogen, total phosphorus decrease gradually along the soil depth. Available nitrogen in 0～50㎝ layer, and available phosphorus in 0～100㎝ layer distribute with a“S”shape along the soil profile. Vertically, these soil nutrient variables vary with obvious stratification and surface accumulation features.3.Heavily intense grazing might result in the decrease of SOM in 0～10㎝ layer, while light grazing and moderate grazing may have an opposite impact. Soil total nitrogen content increase positively with the increasing grazing pressure. The content of soil total phosphorus showed highest at 10～50cm layer in heavily-grazed grasslands. However, soil total phosphorus showed the highest in 0～10㎝ layer of the moderately-grazed grassland. Overall, SOM, soil total nitrogen and total phosphorus showed similar spatial patterns under different grazing pressures.4. The available nitrogen under grazing showed higher than that of non-grazed ones with a limited variation range along the soil profile. With the increasing of grazing pressure, the content of soil available phosphorus increased at 0～10㎝ soil layer, but decreased swiftly at 10～20㎝ in heavily-grazed grasslands. The contents of available potassium in heavily-grazed grasslands revealed higher than that of the other grasslands; and the available potassium of ungrazed grasslands showed the highest at 20～30㎝ layer and 30～50㎝ layer.5.The semi-variograms of SOM, soil total phosphorus and available phosphorus were best described by exponential model; the best model for semi-variogram of soil total nitrogen, available nitrogen and available potassium were spherical model. Among the six types of target soil nutrient components, SOM, total nitrogen and total phosphorus have a moderate spatial dependence, while available nitrogen, available phosphorus and available potassium, have very weak spatial dependence.更多还原