| In arid and semi-arid dune ecosystem, limited precipitation and strong evaporation, make water as one of the restricting factors for the plant growth and survival. And its occupied the large area whose characteristics is water as restriction factors, become the focus of regional ecology and ecohydrology research in China.Based on the integration of meteorological data in recent decades, in the middle part of Naiman in southeastern of Horqin Sandy Land was chosed as the study area. Seven Landsat TM satellite images(1983/1987/1995/ 2004/2007/2013/2015)of the middle Naiman were preprocessed by using Erdas9.2 software, and then interpreted it using Arcgis9.3 software to obtain the mobile dune database. analysis to the changes of mobile dune patches in time and space and the dynamic changes of the fluctuation of precipitation, soil moisture, and mobile dune in regional water balance. In order to analysis the relationship of them, seven towns were chose by using random selection method. The aim of this paper is to the correct theoretical guide for the life and production of local activities and provide theoretical basis to the regional ecological and environmental improvement and sustainable development in the study area.The main conclusions are as follows:(1) the precipitation fluctuation characteristics in 55 years: the time and the value of the largest precipitation in different analysis scale are quite different. From the point of view of precipitation fluctuation, rainfall mainly concentrated from June to August, accounting for 68.02% of the annual precipitation.And the concentration degree of precipitation was 69.22%(±8.12). From the point of view of the decadal precipitation, precipitation in the 1990 s average value was maximum(409.63mm),precipitation average value was minimum(282.6mm) in the last 10 years.From the point of view of the different scales, annual precipitation change trend are basically the same at the scale of 10 years and 15 years. There was a upward-downward-upward trend between 1991 and 2001 as the interval; the variation trend of precipitation are basically the same, mainly in the following descending trend at the scale of 20 years and 25 years. This result shows that the precipitation characteristics of the different time scales maked the trend of precipitation changes different.(2) Mobile dune total area was 113998.84 hm2 in 1983, increased to170398.34hm2 in 1995; it is reduced to72074.26hm2 in 2004. From 2004 to 2013,mobile dune total area was almost unchanged. In view of the overall area change of moving dune, the changing tendency of the total area was decreased. In view of the changing tendency of the patch area, the other three kinds of patch area showed a decreasing trend except for small patches. Relationship between mobile dune patches change trend of total area and precipitation fluctuations showed artificial activity factor is greater than the influence of rainfall fluctuations. There is a consistency between the largest patches, larger patches change and total area change of mobile area and annual precipitation. Small patches and patches are more sensitive to precipitation fluctuations, which can better respond to precipitation fluctuations. Due to the mobile dune area decreased, the ratio in regional total area decreases, the storage water area decreases, it will weaken regulation of mobile dunes on the regional water balance and the regional ecological environment.(3) Spatial variation characteristics of mobile dune soil moisture: Shelihu and Yaoledianzi soil moisture in the vertical direction is a significant downward trend;contrary to K657 and Daliushu soil moisture change trend, a tendency to rise, but not significantly. 4 samples of the soil moisture in the vertical direction of the soil have had a braek point, but not significant, mainly occurred in 60 cm, 120 cm, 200 cm and280cm. Variance analysis of soil moisture in the vertical direction of the 4 samples was carried out, and the minimum variance was obtained with the depth of 60 cm,variance of soil moisture was the minimum, that was the soil moisture stable layer, the soil moisture content was 3.40%. Mobile dune soil moisture characteristic changes of the time: from May to July in the vertical direction soil moisture from shallow to deep decreased gradually;soil moisture in August from shallow to deep was first increased and then decreased, soil moisture in September from shallow to deep gradually increased. 5~8 monthly soil moisture brupt layer was the deep layer of 60 cm, 100 cm,180cm, 200 cm, respectively, in September the brupt layer shallowed, the mutation occurred in 160 cm. The change of soil moisture in mobile dune is influenced by the time and quantity of precipitation. When the precipitation is greater than the mobile dune water storage capacity, the water will penetrate into the soil and further addwater to undergrand.(4) According to the principle of water balance and the area of mobile dune, it was calculated that the total amount of water in the mobile dune was 0.45~5.69 ×109m3 in the last 30 years. the contribution of precipitation to groundwater accounted for about 13% precipitation of the same period. It can be known that in the last 30 years, the contribution of mobile dunes to groundwater is 0.92 ~ 7.93 × 108m3. The amount of groundwater recharge from mobile dune showed mobile dune has a strong water accumulation effect. In recent decades, the area of mobile dunes is decreasing,which is a great improvement in the perspective of vegetation restoration, but the balance between supply and demand of water resources in the region is a negative impact. This result is an important warning to the current emphasis on desertification control in China, while ignoring the positive role of mobile dunes in the natural ecological system.Therefore, in mobile dune management process, it is necessary to grasp the appropriate "degree", retained part of mobile dune, and give play to the role of the mobile dune in the regional water balance,which will promote the benign development of the regional ecological environment. |
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