Study On Soil Salinization And Ecologic Effects In The Typical Oasis Of Arid Regions

Soil salinization is a major type of land desertification and degeneration in the worldwide today. Soil salinization is also a major constraint and obstacle of oasis' agricultural sustainable development in arid and semiarid areas, and poses the enormous threat stably to the oasis ecosystem. Therefore, it has the vital realistic significance to evaluate accurately and prevent scientifically soil salinization in order to promote oasis'agricultural development and regional sustainable development in arid areas.This study selected the delta oasis of Weigan and Kuqa River as the typical research area, which has a long-term researched foundation in Xinjiang's arid area. Under the theory of landscape ecology and sustainable development, used different periods'remote sensing satellite data and long-term field measuring data as the basic data sources, used spatial information technology (RS, GIS, GPS), statistics technology and landscape ecology method, to research synthetically the change of soil salinization and ecologic effects in the delta oasis of Weigan and Kuqa River. Grasping scientific the change rule of the soil salinization and eco-environment in different spatial and temporal scale which could provide scientific basis for the regional eco-environment construction and land sustainable development. At the same time, studying on the change of soil salinization and ecologic effects in the delta oasis of Weigan and Kuqa River is a regional respond to the change of global. Through the research of the regional soil salinization, this thesis indicates some major conclusions as the following:1) Taking the 1989's,2001's TM/ETM+ and 2007's ALOS satellite data as the basic information sources, launch the research of soil salinization change trends. On the foundation of data basic, using the methods of the geography model, transfer matrix, the LUCC model to analysis the change of soil salinization and explored the quantitatively the distribution and the change trends of soil salinization. The results indicate the areas of severely soil salinization presented the obvious decreased trends in the delta oasis of Weigan and Kuqa River from 1989 to 2007; the areas of moderately soil salinization present the fluctuation up and down, but the whole areas was decreased; the slightly soil salinization presented the obvious decreased trends, while the areas of non-salinization showed the trendy of dramatically raise. At the same time, union salty chronometers space interpolation result analysis, the salinized soil is mainly distributed in the lower reaches of the Weigan and Kuqa River, the northern margin of the Tarim River, the west-southern, the southern, and the eastern, the east-southern of oasis. The soluble salt by the chloride primarily, and is accompanied by the few sulfate-chlorination category of things. The distributions of salinized soils are stripe inside oasis, while are slices in the marginal oasis. The main distribution trendy displays the transfer from inside to outside of oasis.2) On the foundation of analysis the satellite data (TM/ETM+ and ALOS), established the spatial and temporal data basic of LUCC in the delta oasis of Weigan and Kuqa River by the combination of RS and GIS. On the foundation of data basic, using the methods of the geography model, transfer matrix, the LUCC model to analysis the change of LUCC, reveal the distribution and change laws of LUCC quantitatively. The results indicate:the whole tendency is the surely increasing of oasis areas in the delta oasis of Weigan and Kuqa River from 1989 to 2007.The type of LUCC showed the continued increasing of the human living region, and the decreased of the natural forest, grass and soil salinization.3) Taking the data of field investigations as the brief data sources, analyzed the spatial distributions of the characteristics of soil salinization. The results indicate:the soil salt content, conductivity, TDS and eight ions assume "T" in three distribution, which is 0-10cm>10-30cm>30-50cm. The salty chronometers gather intensely in the different sample time. The characteristics of soil salinization have different changeability in the space. Using the analysis of correlation and regression to study the relations between the soil compositions, the results indicated the relations of correlation between content of salt with conductivity and K++Na+ are very positive significantly(P<0.01), and the fitful of regression models are very well; the relations of correlation between content of salt with TDS and Cl- are positive significant (P<0.05), and the fitful of regression models are well too; while, the models of regression between content of salt with soil PH, content of water, CO32-,HCO3-, SO42-,Ca2+ and Mg2+ are not significant. Through the principal components analysis, think in this oasis soil system, the soil mantle characteristic available four principal constituents manifests:the first principal components have represented the soil salt chemicals condition, the second principal components and the third principal components have reflected the soil structure condition, but the fourth principal components have represented the soil alkalize characteristic.4) Using the method of numerical classification, analyze the relationship of halophytes with soil chemical factors in the delta oasis of Weigan and Kuqa River. The results indicated that the characteristics of soil salt and soil pH are negative correlative to richness index, diversity index, and evenness index significantly (P<0.05), while are positive correlative to dominance index significantly (P<0.05). Soil salinity and soil PH turned up to be the main determinants to the distribution patterns of halophytes. The soil salinity affects this local vegetation distributed essential factor, simultaneously the soil PH value also lives the vegetation to this area salt the distribution to have certain influence. According to the distribution of vegetation, show Tamarixram osissina, Halostachys caspica with Phragm ites australis distribute to various living environment of salinized soil. These vegetations have wide ecological distribution scope and high ability fitting to salinized soil.5) On the basis of the theory of landscape ecology, referring to methods of landscape pattern ecosystem service values proposed by Costanza R. analyze the ecosystem service value change in the delta oasis of Weigan and Kuqa River. The result manifests that the landscape structural change and the value of annual ecosystem services have significant affections on ecosystem service value. Analysis the losses value of ecosystem service which be caused by soil salinization. The result indicates that the damaged of ecosystem services value by soil salinization is falling from1989 to 2007. The ecosystem service values of forest and grass have much loss, which have large proportions. While, plough and waters which have a little proportions lost little ecosystem service values. Soil salinization causes much ecosystem service values loss to climate control, water source self-control and waste treatment, and little ecosystem service values loss to gas control, soil formed and protected with raw material.Because of the complicated characteristics about the formation mechanism of soil salinization, the study on soil salinization will be synthetically from multi-level, aspects and multiple perspectives, multi-methods. Therefore, on the point of landscape ecology, discovering the dynamic change rule in large scale, studying the correlation, the mechanism of interaction, the salinized region ecology self-restore of soil salinization with ecosystem will be the main considered direction in future research.