Aeolian Sand Movement Law In Coastal Frontier And Effect On The Casuarina Protection Forests

Laws of wind-blown sand movement in the coastal front zone and plant function mechanism is an important part of coast ecology,the research which is based on the blown sand Physics as basic principles, combining theories of forestry, ecology and other subjects is about the characteristic of wind and sand movement and the effect on Casuarina equisetifolia plantation, The objection is to provide the theoretical base and scientific methods to control blown sand hazard and improve the eco-environment in the coastal area of Southern China, the field determination about the sand and wind movement and the effection of the protection forest was made, based on summary of the research fruits of predecessors, three line transect which were parallel to the main wind direction were laid according to the different underlying surface types, the line transect started from the grand calorie climax, followed by Om,5m, 10m,20m,40m and 80m,six different sample points, with experiments outdoors and investigation as main method at Chihu forest farm in chongwu, combining with the analysis of the data of dusty wind weather,studies the whole system composed of blown sand moving process mainly with parallel movement and particle falling process mainly with vertical movement. After anlysis and study, initial results were got as following:1. With the distance to the windward side increased, the speed of different height in each measuring position of forestland and grassland substantially decreased gradually, and the Windbreak efficiency in forestland showed a rising trend on the whole.2. In the three different plots, the soil bulk density was relatively great, the capillary porosity, non capillary porosity, total porosity were relatively small, the soil nature water content was medium in bare land, the soil bulk density was medium, the capillary porosity was relatively great, non capillary porosity was small, the total porosity and soil nature water content were medium in the grassland while the soil bulk density was small, the capillary porosity was relatively, non capillary porosity,the total porosity and soil nature water content were relatively great in the forest land, the capillary porosity, the value of the total porosity and soil nature water content in upper layer increased with the distance from the coast increased, reached the maximum at 40m.3. The surface sand samples in this region are dominated by fine sand, medium sand and coarse sand decreasingly in three different underlying surface, but there were significantly different between the content. Because of the degree of accumulation of sand, the grain size become bigger with the distance increased, the protection forest had the most obvious change and the coarser grain size, the grain size of sub-surface (below 100 mm) were coarser than the surface in the protection forest land and the grassland, but not in the bare land. Due to the coarser grain size, the protection forest land had the highest average particle size, biggest standard deviation is and the highest degree of negative bias compared with the grassland and bare land. Because of the pneumatic separation, there is remarkable correlation between average particle size and other particle size parameters in grassland and bare land, the coarse sand and very coarse sand showed very significant positive correlation with the silty sand so that we could use the content of the coarser sand to distinguish the protection effect of the protection forest, it meant that the coarser sand in the coastal front zone, the better protection effect it had. there was a certain correlation between the characteristics of grain size parameters, the sorting became better and the skewness tended to be positive while the average particle size of sediment became finner. The kurtosis tended to be flattened in grassland and bare land, no significant trends or alterations of kurtosis were observed in forest land.4. The proportion of relative sediment transport rate was lower when the wind speed was greater in 0-2cm height, but it showed a opposite trend in 2-4cm, there were no obvious increase when the height was more than 4cm.the height that most wind and sand movement was 0-4cm, the sand distribution is more uniform in 20-60cm,the few sand quantity was observed in 60-80cm,the phenomenon means that the content of suspended sand was in slight proportion of the whole sand, the total sediment was estimated by the formula of koxmura, Bagnold and Chepil, It is concluded that the estimate of Bagnold formula is reasonable than that of other formulas in the study, the koxmura formula make a great difference with the measured data.5. In forest land, the most sand collection quantity was occurred in January and July, following by the September, it was relatively subdued in other months. The most sand collection quantity was reached in January in grass land, it was relatively subdued in other months. There was no Obviously rule performing in bare land. In forest land, the sand collection quantity showed a single peak curve and reached the maximum in January except the summer, the seasonal whole sand collection quantity was winter>summer>autumn>spring. In grassland, the sand collection quantity showed a single peak curve in winter and summer, the maximum was at 20m and 5m respectively, the seasonal whole sand collection quantity was winter>summer=autumn>spring. There were no similar patterns in the bare land, the annual total sand accumulation of bare land was 7.75 times as much as grass land,216.27 times as much as forest land, the annual change curve of forest land was similar to grass land, the maximum was in January, and then showed a gradually declined trend but increased in June, and reached a new peak value in July, experienced the transience decline in August and then rose gradually. The more the whole sand collection quantity was, the lower the percent of the whole sand collection quantity from 40m to 80m became.6. Correlationship between traits of Casuarina branchlets and distance from the coast was curvilinear, the branchlet diameter diminished while the branchlet length and pitch increased with the distance from coast increased. The branchlet length and branchlet pitch increased quite slowly in a year, the branchlet diameter was more complex, reached the maximum in summer and then rose gradually until the winter that showed a rised trend. The character of branchlet changed mainly before 20m, it changes little after 40m, the branchlet length was significant positive correlated to branchlet pitch the whole year and the branchlet length was significant positive correlated to branchlet diameter except the spring which was only significant positive correlated after 40m from the coast.7. The curves of POD content change monthly were similar at different distances, the maximum value appeared in June, followed by July to September, the minimum value appeared in January, the POD content increased with the distance from coast increased. The contents of MDA were considerably large between October and the next January at different distances and were fewer from March to July. The curve fluctuations were flat with the distance from the coast increasing, the MDA content was decreased with the distance increased except the spring. The maximum value of chlorophyll appeared in July, the contents of chlorophyll were considerably large between May and September, but sharply decreased after October, the contents were few from the October to the next Apirl, the chlorophyl content was increased with the distance increased.