不同风沙条件对几种植物生态生理特征的影响

在野外风洞条件下 ,就不同风况的风沙胁迫对几种固沙植物生态生理特征的影响进行了实验研究。实验采用了沙坡头地区的野外植物和盆栽植物。在不同风速 (5 .9m·s-1,7.9m·s-1,9.9m·s-1,14m·s-1,10m·s-1,15m·s-1,2 0m·s-1)和吹袭时间间隔 (2d ,4d ,9d)下测定了植物 3个生理生态参数的变化。实验结果表明 :1)净风和风沙流胁迫均可使植物的净光合速率 (Pn)降低 ,蒸腾速率 (E)升高 ,从而导致水分利用效率 (WUE)下降。净风和风沙流对植物生理生态特征的影响显著不同。同样为 14m·s-1的风速时 ,风沙流使植物的Pn降低 40 .7% ,而净风使其降低了 35 .88%。 2 )吹袭的时间间隔越短 ,植物的净光合速率降幅越大 ;风沙流比净风的影响更大。在 2d ,4d ,9d为间隔的风沙流吹袭下 ,油蒿 (Artemisiaordosica)的Pn分别下降了 2 0 .13%、11.76 %、7.72 %。风沙胁迫强度越大 ,物质积累越少 ,植物的高生长越慢。 3)由于风沙流降低了水分利用率 ,从而增加了对植物的干燥作用。从总体来看 ,沙生植物对风沙流胁迫有一定的适应响应 ,实验所用灌木较草本植物有更强的抗风性。

Flashover Characteristics of Flat Plate Model Under DC Voltage in Wind-sand Condition

The influence of sand dust on discharge of external insulation has caused widespread concern.At present,the research results show wind-sand electricity has a remarkable effect on the discharge characteristics of insulator and has little influence on the discharge characteristics of air gap.The flashover of insulator strings occurs along the insulator surface and air gaps,and the sand dust deposited on the insulator surface may affect the flashover characteristics of insulator strings.This paper studies the flashover characteristics of flat plate model under DC voltage in wind-sand condition.The experimental results show that under positive polarity voltage,the flashover voltage of the flat plate model has a maximum value,while under negative polarity voltage,the flashover voltage of the flat plate model has a minimum value with a certain degree of sand dust deposition.The wind or sand in sand-dust weather has an important effect on the flashover characteristics of the flat plate model.In certain variation range of electric charge,electric charge of sand dust has little effect on the flashover voltage of flat plate model under DC voltage.The deposition of sand has significant influence on the flashover process of flat plate model,which is related to the deposition density and moisture content of sand particle.