The accumulated sand-belts have formed along the oasis fringe, especially at the upwind areas of the desert area in Gansu Hexi of China during the process of desert control in recent 60 years. The accumulated sand-bel...The accumulated sand-belts have formed along the oasis fringe, especially at the upwind areas of the desert area in Gansu Hexi of China during the process of desert control in recent 60 years. The accumulated sand-belt is a byproduct of desertifieation combating through afforestation and barriers-setting. This pa- per analyzed the data （ including wind velocity/direction） of 21 sites on the accumulated sand-belt to evaluate its stability and ecological effects. The results showed that the accumulated sand-belt is in a stable state. It plays a significant role in weakening wind and this effect is enhanced with the increase of wind velocity. The height of accumulated sand-belt is an important factor characterizing its windproof function. When the wind velocity is higher than 2 m/s, the windproof area in the downwind places is 20 times greater than the height of the accumulated sand-beh. When the wind velocity is higher than 8 m/s, the wind velocity on the top of the accumulated sand-belt is less than that in the upwind open areas. When the air flow reaches the windward slope, its energy is released and reduced by uplifting along the slope and diversion towards the two wings. Wind deflector reduces the velocity of the prevailing wind on the windward slope.展开更多
Accumulated sand-belts refer to those formed along the oasis fringe,especially at the upwind location,due to the accumulation of sand blocked by farmland windbreak. In the 60 years since the foundation of new China,a ...Accumulated sand-belts refer to those formed along the oasis fringe,especially at the upwind location,due to the accumulation of sand blocked by farmland windbreak. In the 60 years since the foundation of new China,a lot of trees have been planted for desertification combating in northwest and north China,thus,accumulated sand-belts were formed at the upwind location. The formation and the ecological effects of the accumulated sand-belts along the oasis fringe is a new scientific concern. To study the formation causes of these belts in Hexi corridor,21 samples were selected,and the height / width of the belts,as well as the vegetation,soil,soil moisture and climatic factors were investigated. This paper analyzed the correlation between the height / width of the belts and the vegetation,soil,soil moisture and climatic factors using the methods of variance analysis,correlation analysis and canonical correlation analysis. The results indicate that: the accumulated sand-belts take a trend of being high and wide in the east whereas low and narrow in the west,and most of the parts tend to be stable; the species on the belts are dominated by Tamarix austromongolica,the vegetation cover and the pure vegetation cover of different dominant species on the leeward slope of the accumulated sand-belts vary significantly. The canonical correlation analysis shows that: the height and width of accumulated sand-belt is the interaction of precipitation,distance to the sand source,leeward vegetation cover and annual average wind speed. Moreover,the height of accumulated sand-belts are negatively correlated to the soil moisture at the depth of 30- 50 cm,air humidity and leeward vegetation cover,and the width of the belts is also negatively correlated with the distance to the sand source. The ecological effects of the accumulated sand-belts are both positive( stopping sands from moving into farmland,protective role as an obstacle)and negative( when the belts decay and activate one day,they will become the new sand sources). At present,there are no signs showing the negative effects of the belts. The ecological effects of the accumulated sand-belts are: firstly the protective role as an obstacle,and secondly to intercept and reduce the sands moving into farmlands.展开更多
基金Supported by National Natural Science Foundation of China(41261102)
文摘The accumulated sand-belts have formed along the oasis fringe, especially at the upwind areas of the desert area in Gansu Hexi of China during the process of desert control in recent 60 years. The accumulated sand-belt is a byproduct of desertifieation combating through afforestation and barriers-setting. This pa- per analyzed the data （ including wind velocity/direction） of 21 sites on the accumulated sand-belt to evaluate its stability and ecological effects. The results showed that the accumulated sand-belt is in a stable state. It plays a significant role in weakening wind and this effect is enhanced with the increase of wind velocity. The height of accumulated sand-belt is an important factor characterizing its windproof function. When the wind velocity is higher than 2 m/s, the windproof area in the downwind places is 20 times greater than the height of the accumulated sand-beh. When the wind velocity is higher than 8 m/s, the wind velocity on the top of the accumulated sand-belt is less than that in the upwind open areas. When the air flow reaches the windward slope, its energy is released and reduced by uplifting along the slope and diversion towards the two wings. Wind deflector reduces the velocity of the prevailing wind on the windward slope.
基金Supported by the Pre-phase Project of the 973 Program(2014CB460611)
文摘Accumulated sand-belts refer to those formed along the oasis fringe,especially at the upwind location,due to the accumulation of sand blocked by farmland windbreak. In the 60 years since the foundation of new China,a lot of trees have been planted for desertification combating in northwest and north China,thus,accumulated sand-belts were formed at the upwind location. The formation and the ecological effects of the accumulated sand-belts along the oasis fringe is a new scientific concern. To study the formation causes of these belts in Hexi corridor,21 samples were selected,and the height / width of the belts,as well as the vegetation,soil,soil moisture and climatic factors were investigated. This paper analyzed the correlation between the height / width of the belts and the vegetation,soil,soil moisture and climatic factors using the methods of variance analysis,correlation analysis and canonical correlation analysis. The results indicate that: the accumulated sand-belts take a trend of being high and wide in the east whereas low and narrow in the west,and most of the parts tend to be stable; the species on the belts are dominated by Tamarix austromongolica,the vegetation cover and the pure vegetation cover of different dominant species on the leeward slope of the accumulated sand-belts vary significantly. The canonical correlation analysis shows that: the height and width of accumulated sand-belt is the interaction of precipitation,distance to the sand source,leeward vegetation cover and annual average wind speed. Moreover,the height of accumulated sand-belts are negatively correlated to the soil moisture at the depth of 30- 50 cm,air humidity and leeward vegetation cover,and the width of the belts is also negatively correlated with the distance to the sand source. The ecological effects of the accumulated sand-belts are both positive( stopping sands from moving into farmland,protective role as an obstacle)and negative( when the belts decay and activate one day,they will become the new sand sources). At present,there are no signs showing the negative effects of the belts. The ecological effects of the accumulated sand-belts are: firstly the protective role as an obstacle,and secondly to intercept and reduce the sands moving into farmlands.
