The Study On Dynamic Change And Prediction Of Soil Water Content Under Different Sand-fixing Modes On Shifting Dune

The desertification of land has already become one of our country's most serious ecological environment problems, and sandstorm aggravating constantly makes ecological environment more serious. The shifting dunes is regarded as one of the main sources of the sandstorm, it causes the large area farmland to bury, bury villages, roads etc, and causing the enormous economic losses, so, the work of harnessing shifting dune has been already very urgent, the success or failure is influencing the progress of the whole desertification preventing and controlling. And the soil moisture state is the important condition of the success or failure in the vegetation recovery and controlling sands. The soil moisture is regarded as a key factor of the SPAC;it not only influences the characteristic of the soil and growth of the plant directly, but also influences plants to distribute and the changes of the local conditions to a certain extent indirectly. With development of the vegetation in harnessing sand, soil moisture of sand dune appears obviously downward trend, moisture enough becomes the most baffle, the whole system has presented the unstable phenomenon, the vegetation is weak ahead of time. So, it is the key point of fixing the sand for a long time and the vegetation recovery that taking measures to raise the content of the soil moisture, and improve the utilization ratio of the limited precipitation, and it is of very important realistic meaning.Because of the above background, based on forefathers foundation of the harnessing sand modes that originally test, drawing forefathers successful experience and lesson of harnessing sand mode.At the shifiting dunes, chemistry methods and sand of grass bar hinders were taked in fixing the sand separately, and plant different areas in the plant district and chemisty districts to match and forms different modes, and utilized sand dune slope location advantage, change soil moisture surface flow increase biological soil moisture content of district, so as to ensure the normal growth of the vegetation, the survival rate of the vegetation is improved.During the experiment, soil moisture content of the moving-dune was measured regularly with neutron moisture apparatus. Then, through comparing the soil moistures content of different harnessing modes, comparing the soil moisture content of harnessed areas with that of naked areas, higher soil moisture content of harnessing modes was selected. At last, the soil moisture (0-30cm soil depth) of planting areas with higher soil moisture content of harnessing modes was forecasted, and then the conclusions were drawn as follows:1. Application of neutron apparatus and the method of demarcatingThe research had verified that neutron moisture apparatus has practical and credible application to harness the moving-dunes. Furthermore, the research also had found that demarcating equation, combined with a slice-paragraph demarcating method and linear/non-linear regression method, had high precision and can be spread.2. Analysis of soil moisture content of harnessed areas through harnessing modes with chemical measuresBased on the analysis of the time-series soil moisture content of harnessed areas with different measures, the conclusions of different parts and soil depth of the moving-dune were all different eachother. On the top of the dune, in 0-30cm soil depth the soil moisture content of the harnessed area through first harnessing mode (harnessed area with chemical measure was 8m width) was the highest;in 3O-8Ocm soil depth that through the fourth harnessing mode(harnessed area with chemical measure was 6m width) highest. At the middle of the dune, in 0-30cm soil depth that through the sixth harnessing mode (harnessed area with chemical measure was 2m width) was the highest;and in 3O-8Ocm that through the fourth mode (harnessed area with chemical measure was 6m width) was the highest. 3. Dynamic simulating and forecasting of soil moisture with different simulating methods On the basis of dynamic simulating and forecasting the soil moisture content with the methods of the exponent smooth and self-regression model and BP neural net model, some conclusions as bellow: the current soil moisture content of the dune was influenced by that of the dune during former two month;the modeling and forecasting precision of BP neural net model was higher than that of other methods. But, all in all, the soil moisture content of the dune had been on the downside.