| Soil moisture is the main limit factor of growth-development and recover-reestablish of vegetation, influence plant live, growth-development and the supportiveness of environment on the vegetation, then decides the success or failure of the vegetation restoration and reconstruction in a large part, and also have been the research hotspot of ecology, pedology and ecohydrology in arid and semiarid regions. Artificial shrub that represented by caragana korshinskii played an important role to break wind and fix sands in in arid and semiarid regions. But soil moisture significant decreased and formed dried soil layer with increasing of its age and density. In addition, the buried depth of ground water is often deeper, so precipitation is the important water source that needed by the vegetation. Different rainfall events, that include large rainfall events what’t ontribution to the total rainfall is larger and little rainfall events that’s proportion is more, played an important role in soil-vegetation water cycle, but existed a certain difference. Therefore, the research of the dynamics and response of soil moisture to rainfall pulse to grasp soil moisture effect of artificial caragana korshinskii forests in desert steppe has important study significance.Caragana korshinskii, that is the vulgo of the cultispecies-caragana fabr-leguminosae sp. and widely distributed in the various provinces and regions in north China, is the main afforestation species of break wind-fix sands and conservation of water-soil. Over the years, the area of caragana korshinskii that’s afforestation area has been maximum and that’s areal distribution has been the most widely has reached518,000hm2, thereinto artificial planting area occupy94.12%. To grasp soil moisture effect and provide a scientific basis for the sustainable development of the artificial caragana korshinskii forest in desert steppe, taking artificial caragana korshinskii forests in Yanchi Ningxia as the research object, combining the basic theory of soil genesis and restoration ecology, and applying the method of field observation&indoor analysis, fixed time and location, this paper studied the soil moisture dynamic of artificial caragana korshinskii forest with different ages, different mowing measures and different mowing years, discussed the response of it to rainfall pulse. The main results and conclusions are as follows:(1) The rainfall frequency decreased with increasing of rainfall class in study area.≤5mm rainfall events were major and large rainfall events(>10mm) were infrequent in the rainfall pattern, but the contribution of it to the total rainfall is larger. Average monthly distribution of≤5mm rainfall events and its rainfall were stabilized. The proportion of inter-rainfall period of≤3d was the most and its variability was relative small, and its average monthly distribution was stabilized. In conclusion, the rainfall pattern in study area showed the typical pulsating characteristics.(2) The consuming water depth of artificial caragana korshinskii forest in study area become shallow gradually, soil water content decreased, and the thickness of dried soil layer augmented with increasing of its age. The layer of soil water utilization of7a,16a,25a,37a age forest were10-180cm、 10-260cm、10-160cm、10-100cm separately. The soil moisture throughout the growing season of7a,16a age forest were greater than7%, but the soil moisture of belowed200cm soil layer of7a age forest apparently higher than16a age forest, and its maximum value reached27%. The soil layer that its soil moisture belowed7%of25a,37a age forest distributed belowed150cm and100cm. In conclusion, soil moisture of artificial caragana korshinskii forest with different ages degenerated gradually with increasing of its age.(3) Rainwater collection of canopy and water deprivation of root system of artificial caragana korshinskii forest were obvious and decreased with increasing of the distance to roots.(4) Response of soil moisture to rainfall pulse of caragana korshinskii forests in study area decreased with increasing of soil depth and of the distance to roots. Response of soil moisture of deeper layer to rainfall pulse have obvious hysteresis. Because the rainfall and soil evaporation were offset, the response to<5mm rainfall was unconspicuous, when the response to>10mm rainfall was conspicuous.(5) Rainwater collection of canopy, soil water infiltration capacity and the spatial variation of soil moisture weakened after mowed caragana korshinskii. The improvement of complete mowed measure to soil water was better than interleave mowed measure.(6) The results of soil moisture variation of Caragana korshinskii forests with different mowing years showed:soil moisture has not been improved in the first year after complete mowed measure, even the degree of degeneration was some slightly deeper. Then soil moisture first increased and then decreased, and the thickness of dried soil layer first shrinked or even disappeared then to deteriorate with increasing of restore period. The third year was the turning point of soil moisture succession after complete mowed caragana korshinskii. |
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