| Tamarix Cone is the shrub dune containing clear sedimentary veins in extremely arid area depositing around the Tamarix.It is a unique biological landform in the desert surrounding which comes into being by the long period of interaction of Tamarix and wind-drifting sand.Tamarix Cone distributes in groups in the south edge of Taklimakan Desert,the banks of the downstreams of Tarim River,Hotian River,Keliya River,Chelchen River,and Kongque River,as well as the delta areas and the old streams and local depressions. The deadwood and the fallen leaf layer and the sand layer of Tamarix deposit in turns can form the clear bedding structure named "annual stratum".It is the record of annual growth rate of sand dunes.The thickness of the "annual stratum" mainly depends on the intensity of wind,the times of sandstorm and the amount of growth of Tamarix in that year.Owing to the arid climate,the "annual stratum" can be conserved for a long time.Theoretically,the resolution of the sedimentary veins can reach the year degree,which may be used to count the ages.The aeolian sand and Tamarix leaf of the "annual stratum" of Tamarix Cone contain much environment information.The analysis on the compositions of Tamarix Cone can be utilized to research and restore the changes of climate and environment hundreds of years ago, and is one of the powerful tools for researching the changes of environment in the arid area. So it has a very vital significance in the study of evolvement of ecological environment in arid desert area.Lop Nur region is located in the eastern Tarim Basin.Its north is Kuruktag Mountain, northeast is Keziletag Mountain and Yigtag Mountain,the east is Baishan which is boundry between Gansu Province and Xinjiang,the south is Altun Mountain,and the west is Taklimakan Desert and Kumtag Desert.The eastern Aqik Valley is connection with the Shule River and Hexi Corridor.The topography appears an inverted bottle.Lop Nur is the destinations of the rivers in Tarim Basin.Its environmental evolution is an epitome of that of Tarim Basin and nearby mountains.The area belongs to extremely arid warm temperate continental climate.It has little rain,large amount of evaporation,and big annual range of temperature and day range of temperature.The climate in winter is dry and cold,and in summer is hot and little rain.Lop Nur region belongs to desert zone,which is sensitive to climate change and is a good place to study global changes in the past.The desert zone is an important part of the global system,and has unique characteristics in the aspect of environment changes.Hencethe science system of global change needs the researched results about environmental changes in this area.The research method is by choosing Tamarix Cone of Lop Nur region as the chief research subject,and together with document investigation,the combination of field observation and laboratory analysis and testing,and the combination of basic research and the applied basic research.Field work is mainly on general investigation of field environment,the choice and measure of classical Tamarix Cone and collection of the samples.The laboratory work is mainly on the experiment analysis of the samples,and the procession,and analysis of the data.The data of organic matters such as TOC,TN,C/N and thickness of the sand layer are analyzed in the comparison of two samples in 2007 and those in 2003 of Tamarix Cone in Lop Nur region.And in the aspects of TOC,TN,C/N of Tamarix Cone as well as thickness of sand layer,the temperature,and rainfall,we sub-study the temperature and rainfall in different periods of Lop Nur,and initially revealed the environmental changes during past 168 years in Lop Nur region,and then make a further research and discussion on climatic and environmental situation of Lop Nur and its edge region.Also there is comparison with other researches,and improvement of the means of how to research the environmental changes of arid area with high resolution taking advantage of sedimentary veins of Tamarix Cone,then the summary for TOC,TN,and C/N of Tamarix Cone in different places by correlation analysis,linear regression.By the analysis of Tamarix, different types of plants,comparative analysis of the sediments,it reflects Tamarix Cone's unique function to characterize regional environment evolution and soil desertification.The basic conclusions are as follows:(1)We have analyzed the relationship between TOC%,TN%,and C/N and temperature and rainfall of Tamarix Cone in Lop Nur region,as well as the relationship between the thickness of sand sediment and rainfall,that is,TOC%and TN%of Tamarix decreases,while the ratio C/N increases,reflecting the ambient temperature and humidity increasing.The thicker sand,the smaller humidity shows little rainfall,and vice versa.That also can be said the content of TOC%and TN%have a negative relationship with temperature and rainfall, C/N has a positive one.And the thickness of sand layer is a negative correlation only with rainfall.According to it,the time for recent 168 years in this area can be divided into several different stages,1839～1858(warm and dry climate),1859～1910(cold and dry climate, cold and wet climate after beginning of 20th century),1911～1950(warm and wet climate), 1951～1962(cold and dry climate),1963～2006(warm and wet climate,cold moisture climate from 1978 to 1982 with low temperature).(2)The related relationship among TOC%,TN%and C/N of Tamarix defoliation indicates that TOC%and TN%is positively linear related much dramatically.TOC%and C/N have no obvious relationship,and its linear relevance is poor.TN%and C/N have a high negative linear correlation.(3)TOC%of Tamarix defoliation is close to that in the middle reaches of Yangtze River, and less than that of some types of mountain plants,TN%less than that of the selected sample plants,while C/N is greater than that of selected plants,heightening the barren soil,low nutrition elements in the district.(4)The value of TOC%,TN%and C/N in the sediment of Tamarix Cone is higher than or similar to indicators in average sediments. |
PDF Full Text Request