| Transitional zone between oasis and desert in the upper reaches of the Tarim River belongs to thesensitive eco-environmental areas, as well as bio-diversity protection in China and one of the key areas ofglobal change research, interference from the outside world, especially to human activity as the leadingregional land and water resources development response is more intense. The Valley has changed fromnatural oasis to artificial oasis ecosystem, and desert vegetation reduced year by year, losing themaintenance of ecological balance of its powerful features. The purposes of this test is to providetheoretical foundation for the restoration and protection of transitional zone between oasis and desert byusing the way of dropping and flooding to the soil, groundwater and vegetation of it. And the results of thestudy are as follows:1. The Composition of Plants in Transitional Zone between Oasis and DesertThere are37species belonging to27genera and12families in which dicotyledonous plants aredominant in the transitional zone between oasis and desert of the upper reaches of the Tarim River, andplant species is relatively poor, so is diversity. The flora composition of this area has10types,2subdivisions, Mediterranean is prevailing, and temperate also occupies a certain position, belonging to thearid desert plants.2.The analysis of the Age-class structure and distribution pattern of Populus euphratica forest and speciesdiversityNear the farmland grade two population age structures are complete, stable populations; on the contrary,the two away from the farmland are incomplete, they are the waning populations. And flood irrigation nearthe river’s stocks of two the samples belong to stable populations while those away from the river arewaning populations. Plot close to the farmland is random distribution and the rest are clustered distribution.Under the drip irrigation, the distance in desert oasos ecotone changes from near to the distant, diversityindex decreased gradually, and the differences are extremely significant, irrigation of the four speciesdiversity index changes irregularly.3.The changes of the ground water in the oasis desert transition zone under the irrigation of dripping andfloodingThe underground water level of the four observation wells under drip irrigation is between1.94~2.91m,the distance to farmland changes from the near to the distant, and the annual average groundwater increasesgradually (P<0.01); In April, the groundwater is extremely more shallow than the rest months. Theunderground water level is between1.15~5.28m under the flood irrigation of the four observation wells,and the distance changes from the near to the distant river, the annual average groundwater deepengradually, and the differences are not significant; from March to June, groundwater is buried extremelydeep compares with the other months; from July to November, the annual average groundwater becomesshallow gradually (P<0.05). Under the drip irrigation and flood irrigation, the groundwater of the desertoasis ecotone is alkaline, among anionic, Cl-and SO2-4own the highest content, and among the cationic, K+and Na+possess the highest content while HCO3-, Ca2+and Mg2+are relatively lower than the others.Salinity in the nearest observation wells of the drip irrigation farmland is higher, it is3.34g/l, and salinitydecreased gradually from the near farmland to the distant; while salinity is higher in the most distantobservation wells and it is1.07g/l. 4.The changes of soil factors in desert oasis transitional areasSoil pH is between8.10and9.04under drop irrigation, and the pH decreased gradually from the near tothe distant of farmland, and the differences are not significant. Soil pH sample under irrigation is between8.12and8.94, and among the plots, soil PH is not significantly different. Different soil has different soil PHunder the drip irrigation and flood irrigation.Under drip irrigation, the soil PH varies between8.10and9.04. From the near to the distant distancefrom farmland, the soil pH value decreases gradually, which shows no significant differences. Underirrigation, sample soil PH varies between8.12and8.94, which also shows no significant differences. Riverfrom near to the distant distance, soil moisture content of desert oasis ecotone decreases gradually; the soilmoisture content increases with the increase of soil depth; the soil total salt content decreased with theincrease of soil depth. Higher as total salt content remains in surface, it shows significant difference. Underirrigation, with the distance changing from farmland, the total soil salt content decreased gradually; whilethe total salt is not regular with the changing of distance. Total soil content is the highest that is far fromriver. Based on the determination of physicochemical properties of soil, the desert oasis ecotone under dripirrigation, soil organic matter, total nitrogen, available nitrogen, available phosphorus content in the upperlayer soil is higher than the lower content. The soil physicochemical property of sample soil that is near tofarmland is higher than other sample soil, which shows significant differences.5.Analysis the oasis desert transition zone between the various environmental factors under the irrigation ofdripping and floodingBy gray correlation analysis showed that the organic matter, total nitrogen, total phosphorus, totalpotassium and potassium with the oasis desert transition zone species diversity has a greater relevanceunder the irrigation of dripping and flooding. Under the drip irrigation on species diversity of groundwaterchemical type to Cl--Na+based, irrigation with Cl--SO2-4-Na+-K+based. Through the correlation analysisshowed very significant correlation between the oasis desert transition zone salinity under the irrigation ofdripping and flooding and eight ions, and eight ions, a significant correlation between the index of speciesdiversity. The main factors affecting the Simpson index of total salt in soil, soil water content, organicmatter,and significantly correlated with soil total salt under the drip irrigation. various soil factors andSimpson index no significant correlation under the flood irrigation. Simpson index with the water salinity,pH and Eight ionic has a very significant correlation under the drip irrigation. the oasis desert transitionzone Simpson index and groundwater, water salinity, pH, moisture eight ions were not significantlycorrelated. |
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