杨树-玉米林网系统内光强空间变化特征的研究

Characteristics of light intensity in different age poplar forest network system

2010～2012年对杨树林网系统内光量分布和透光率的监测实验表明,在玉米生长的各个时期,随着距树距离的增加,光合有效辐射量呈现增大趋势,并且在15 m内变化幅度较大,15 m外随着距离的增加光合有效辐射量缓慢增加至对照点处数值;2012年与2010年相比各测点透光率分别降低9.88%、8.57%、12.02%、2.23%、0.87%;利用2010～2012年3 a数据对杨树林网系统内不同距离范围内玉米透光性的研究结果显示,当距离和树高比(X)为0.1、0.5、1时,系统内的透光率分别为43.03%、75.20%、92.92%,受遮荫率则分别为56.97%、24.80%、7.08%;系统内1.5 m、7.5 m观测点处光合有效辐射量和透光率受林木的遮荫影响较大,其它各测点处受遮荫影响较小,并且林木的遮荫在15 m范围内。

Based on the main factors of photosynthetic active radiation measured in the farmland shelter forest network from 2010 to 2012, the photosynthetic effective radiation and light transmittance in different stages of maize growth periods were analyzed. The results show that with the increase of the distance from maize to tree, the photosynthetic active radiation （PAR） presented the increasing tendency. The light intensity distribution and the light transmittance changed relative greatly in the range of 15 meters tree- maize distance, and when beyond 15 meters tree-maize distance the two indexes＇ increasing amplitude slowed down and reached the position of control point; compared the 2012 to 2010, the light transmittance decreased by 9.88%, 8.57%, 12.02%, 2.23% and 0.87%, respectively. The light transmittance values of different tree-maize distance in the poplar forest network system were measured from 2010 to 2012. The results show that when the distance and tree height （X） were 0.1, 0.5, 1.0, the light transmittance was respectively 43.03%, 75.20% and 92.92%, and shading rate was 56.97%, 24.80% and 7.08% respectively. In the system, the photosynthetic effective radiation and light transmittance at the observation points of 1.5 meters and 7.5 meters were greatly affected by shading degree, and the other observation points were less affected. The shading degree was gradually improved with the increase of forest age. Comprehensive analysis showed that the sphere of influence on light intensity of maize growth period was in range of 15 meters in farmland shelter forest network system.