三种人工林分的冠层结构参数与林下光照条件

Canopy structural parameters and understory light regimes of 3 artificial forest stands in South China

关键词:  冠层结构  林冠孔隙度  叶面积指数  半球面影像技术

Key words:  canopy structure  canopy openness(CO)  leaf area index(LAI)  hemispherical photography

摘要:

以样方法为基础，用半球面影像技术测定了桉树林、湿地松林和混交林（木荷＋青冈＋银木荷）3种人工林分的冠层结构（叶面积指数LAI和林冠孔隙度CO）和林下光照条件（林下直射光TransDir和林下散射光TransDif），并分析了冠层结构与林下光照条件之间的关系。测定结果表明，桉树林、湿地松林和混交林的LAI平均值分别是1.9、2.7和2.6，变异系数为11.3%，14.4%和19.3%；CO的平均值分别为18.1%，10.4%和11.0%，变异系数为13.9%，17.7%和26.2%；TransDir的平均值分别为6.5，4.0和3.9 mol•m 2•d 1，变异系数为22.1%，22.9%和30.8%。TransDif的平均值分别为5.5、3.2和3.3 mol•m 2•d 1，变异系数为15.2%，14.8%和19.2%，以混交林林下光照的空间异质性最明显。相关分析表明，在3种林分中，TransDif均与LAI或CO显著相关，而TransDir仅在混交林中与LAI或CO显著相关。混交林冠层结构具有较高的空间异质性，并直接影响林下光照条件。

Abstract:

Canopy parameters and understory light regimes of three artificial forest stands in South China，i.e.，Eucalyptus，slash pine and mixed forest stands，were estimated using hemispherical photography based on quadrat method together with plant census，and the relationship between canopy structure and understory light regimes was analyzed. Leaf area indexes(LAI)of the 3 artificial forest stands were 1.9，2.7，and 2.6，respectively，and their CV(coefficient of variation)was 11.3%，14.4%，and 19.3%，respectively. Canopy Openness(CO)was 18.1%，10.4% and 11.0%，and their CV was 13.9%，17.7%and 26.2%，respectively；Transmitted direct gap light(TransDir)was 6.5，4.0 and 3.9 mol• m 2•d 1，respectively，and their CV was 22.1%，22.9%and 30.8%，respectively. Transmitted diffuse gap light(TransDif)was 5.5，3.2 and 3.3 mol•m 2•d 1，respectively，and their CV was 15.2%，14.8% and 19.2%，respectively. High spatial heterogeneity in understory light regimes was found in the mixed forest stand. Correlation analysis indicated that in all the 3 forest stands TransDif was significantly correlated with LAI or CO，while TransDir was significantly correlated with LAI or CO in the mixed forest stand. Canopy structure of the mixed forest stand exhibited higher spatial heterogeneity and had a direct impact on understory light regimes.