策勒绿洲边缘新疆杨防护林疏透度的季相变化

Seasonal Variation of Shelterbelt Porosity of Populus alba var. pyramdalis at the Edge of Cele Oasis in the South of Tarim Basin

2013年对策勒绿洲边缘的新疆杨防护林疏透度进行了全年观测。结果表明:1新疆杨防护林带疏透度随树木生长依次经历了:缓慢下降初期(3月9—31日)-快速下降期(4月1—18日)-缓慢下降末期(4月19日至5月12日)-低位稳定期(5月13日至10月20日)-快速上升期(10月21日至11月20日)-高位稳定期(11月21日至3月8日),其中,在快速下降期,仅半个月,防护林即可达到较为稳定的防护效应;2在春季早期,风沙活跃期与防护林稳定防护效应的形成期存在相位差,加强早春防护力度以减小相位差对于抵御风沙危害,保证作物生长有着积极且重要的作用;3虫害的发生使防护林稳定防护效应的形成时间晚了近1个月,这与人为管理不得当密切相关,同样,虫害、病害、倒春寒等一系列危害都会对防护林稳定防护效应产生影响,防护林的人为管理需引起重视。

The seasonal changes of shelterbelts will cause an obviously difference of porosity. Shelterbelt protective effects are closely to porosity. The study of porosity variations can help us to understand the shelterbelts ＇effect. In order to get the Populus alba var. pyramdalis shelterbelt porosities in 2013,we conducted the method of digital image on the edge of Cele Oasis. The results showed that：（ 1） during the year,P. alba var. pyramdalis shelterbelt porosities experienced： slow decline in the early（ March 9-March 31）-period of the rapid decline（ April 1-April 18）-slow decline in the late（ April 19-May 12）-low stable（ May 13-October 20）-period of rapid rising（ October 21-November 20）-high stable（ November 21-March 8）. In the period of the rapid decline,with only half month,P. alba var. pyramdalis shelterbelt can quickly reach stable protective effect;（ 2） The formation of shelterbelts stable protective effect differ from the active occurrence of sandstorm in time. Strengthening the protection effect of early spring plays a positive role in resisting sand damage and protection crops growth;（ 3） Bad management will have a greater impact on the protective effect of shelterbelt. Incidence of pests delayed best protective effect for a month. Therefore,shelterbelt management needs more attentions.