Study On Soil Physical And Chemical Characteristics Under Different Land Uses In Qinghai Lake Area

The Tibet Plateau due to its high altitude, large temperature difference between day and night, low vegetation coverage and biodiversity, it becomes the sensitive area of global change and the ecosystems fragile area. While Qinghai Lake as an important part of the plateau, located in the western arid region, eastern monsoon area and Tibetan Plateau region of the three major convergence zone, are the important part of wave.to maintain ecological safety in the Northeastern Tibetan Plateau. In recent years, however, affected by the global change and human activities,the lake grassland degradation and aggravation of desertification trends make it has become a potential erosion area.What kind of development trend will be in the change of land type around the lake under the natural environmental change and human disturbance is particularly important to Qinghai Lake ecological protection and sustainable development. The basic soil physicochemical properties is the basis research of soil environment and the entire ecosystem, The analyses of soil physic chemical properties under the same parent material in different land use ways are rarely seen. So confirmed grassland and farmland on the same parent material around Gangcha County in northern of Qinghai Lake as a research area on the early basis analysis of surface layer soil particle size and the remote sensing interpretation map of 1987,2000 and 2010 in Qinghai Lake basin. To search for the soil succession law under different land use ways through analyzing the samples variety and difference of soil particle size, mineral composition, organic elements, magnetic susceptibility, chromaticity and ph,in order to provide theoretical support for ecological environmental protection of the study area and even the surrounding region of Qinghai Lake. The results show:1. The average content of soil particle size composition of grassland are silt(70.8%), clay(20.22%) and sand(8.98%), the average content of soil particle size composition of farmland are silt(70.8%),clay(20.22%) and sand(8.98%);The overall composition of soil particle size on the farmland is greater than the grassland on a lengthways profile, soil particle size composition differences in particular above 30 cm, farmland size frequency curve has multimodal and coarsening trend, mostly grassland have the characteristics of bimodal size frequency curve(a peak and a second peak) in aeolian loess deposition. Grassland and farmland soil particle size have smaller otherness below 30 cm and size frequency curve characteristics tend to aeolian loess, indicating soil parent material of the study area is aeolian loess;2. The average contents of soil total carbon in grassland and farmland are 3.15% and 2.82% respectively, the average soil nitrogen contents are 3.15% and 2.82%, the average C/N of grassland and farmland are16.66 and 19.4, total carbon and nitrogen contents of grassland are greater than farmland above 30 cm,while the differentiation between grassland and farmland is smaller below 30 cm, in addition the total carbon and nitrogen maximum content of grasslands in 0-10 cm segment, of farmland in 10-20 cm segment.3. Grassland soil detected in seven kinds of minerals, followed by the content in turn is the quartz, albite, calcite, muscovite, clinochlore oblique, dolomite, magnesite, farmland soil is not detected magnesite, the mineral content in turn is quartz, albite, calcite, muscovite, clinochlore, oblique, dolomite. Grassland soils except quartz content less than farmland, the rest of mineral content greater than farmland; the albite content of grassland greater than farmland above 30 cm, it’s content in 30-50 cm segment is small, the muscovite and clinochlore content of grassland greater than farmland above 30 cm,and smaller below 30 cm.4. The average Xlf of grassland and farmland are 46.11×10-8m3kg-1 and 54.33×10-8m3kg-1. The average Xfd of grassland and farmland are 7.22% and 6.96%,the Xlf of grassland is smaller than farmland on the whole profile, the Xfd of grassland is greater than farmland above 30 cm, indicating a higher intensity of pedogenesis than the farmland,there is a small otherness between grassland Xfd and farmland Xfd below 30 cm.5. The average of ph of grassland and farmland were 8.42,8.38, were alkaline, the ph of grassland is greater than farmland in lengthways profile, the ph of grassland is greater than farmland above 40 cm, and smaller below 30 cm.6. Farmland chromaticity value(lightness, redness, yellowness) is greater than the grassland on the whole, the lightness of grassland has increase trend and of farmland has decrease trend above 30 cm, the lightness of grassland and farmland have no otherness change below 30 cm, while the change of redness and yellowness in lengthways profile just the opposite with lightness.7. The correlation between different physical and chemical properties index are influenced by different ways of land use obviously. Due to smaller external disturbances,the soil particle structure in grassland was closely and the particle size also correlated significantly with total carbon, total nitrogenand chromaticity, but there was no remarkable correlation with ph; due to greater external disturbances, the farmland has less soil fine fraction and has no significant correlation with total carbon, total nitrogen or chromaticity, but there was significant correlation with ph, the magnetic susceptibility has significant correlation with the granularity of grassland and farmland,but the otherness were small.Overall, the grassland and farmland soil of study area have similarities and differences by a formation depth of 30-35cm: soil physical and chemical properties of grassland and farmland have significantly difference above 30 cm,indicating that the above 30 cm of soil was the main human activities disturbance stratum, and the impact of agricultural production mainly concentrated in this range, the soil physical and chemical properties of grassland and farmland has no significantly difference below 30 cm, indicating thatsoil evolution will tend to homogeneityin the case of human activity does not interfering or lesser intensity. It can be compared with soil physical and chemical characteristics between farming and grazing that: farmland soil physical and chemical indicators are quite different at different sampling points, have a significant spatial heterogeneity. Soil particle size of farmland takes on the characteristic of coarsening, organic carbon and organic nitrogen are significantly lower than the grassland, the indication of grassland and farmland such as magnetic susceptibility and mineral composition shows that the intensity of pedogenesis of farmland is lower than the grassland, the farmland of the study area at the risk of land desertification exists desertification risk, and in the Qinghai Lake area, grazing pattern will be a more rational land use patterns.