LAI-2000冠层分析仪在不同植物群体光分布特征研究中的应用

The Utility of LAI-2000 Canopy Analyzer Studying the Sunlight Distribution Characteristics in Different Plant Colonies

目的寻求快速准确确定各种农林植物冠层透光率及其随时间变化规律的方法,以及通过冠层分析确定农林植物冠层消光系数的方法。方法应用LAI-2000冠层分析仪和LI-1400数据采集器连接LI-190、LI-191传感器,测定了高秆作物(玉米)、矮秆作物(大豆)和林木群体(楸树、白蜡、栾树苗圃幼林冠层)的LAI、叶倾角、冠层开度及群体透光率。结果(1)LAI-2000测得的冠层开度,与全天群体透光率相关非常密切。相关系数达0.9308,回归直线的截距为0.015,接近于0,斜率为1.0668,接近于1。所以,完全可以使用冠层开度估计透光率。阴天比晴天估计效果更好。(2)用实测的LAI和群体透光率,准确计算出了农林植物群体的消光系数。消光系数有明显的日变化,玉米冠层一日中出现两个极大值,中午最低。结论LAI-2000冠层分析仪能给出群体内不同天顶角方向的天空开度,能更详细地表达植物群体结构特征;群体内某一点的冠层开度与该点的冠层透光率在数值上几乎相等,所以冠层内透光率测定不再需要冠层上下同时测光计算,而直接由测冠层开度得到;LAI-2000无损测定冠层LAI,可用于计算群体消光系数,文中所计算的消光系数,处在文献报道的正常范围。

[Objective] To seek a fast and accurate method for determining the light transmission rate and extinction coefficient.[Method]The LAI, foliar obliquity, canopy openness and light transmission rate in different plant colonies were measured using canopy analyzer LAI-2000 and the solar radiation instruments including the data logger LI-1400, solar radiation sensor LI-190 and LI-191. [Result] （1） the canopy openness measured by using LAI-2000 had a very close relationship with the sunlight transmission rate of the colonies. The correlation coefficient was 0.9308, the intercept of the regression line was 0.015, which was almost equal to 0, and the slope was 1.0668, which was almost equal to 1. So the canopy openness could be used to estimate the light transmission rate, and the cloudy weather was more suitable. （2） Using the measured LAI and colony light transmission rate, the extinction coefficient of different canopies were calculated accurately. Under the corn canopy, the extinction coefficient changed clearly during the daytime. It had two maximum values and one minimum value. The minimum value happened in the noon. [Conclusion] LAI-2000 canopy analyzer can provide the sky openness of different zenith angles, so it can describe the colony structure in detail; The canopy openness under the canopy is almost equal to the light transmission rate, therefore the measurement of light transmission rate no longer needs the light measurements of over and under the canopy. The LAI of agricultural and forestry canopy measured by LAI-2000 without damaging the colony can be used to calculate the extinction coefficient, and the extinction coefficient calculated in this paper is close to those reported in the references.