杭州湾北岸沿海防护林冠层结构及林下光环境

利用跟踪辐射与冠层结构测量仪（TRAC）研究了杭州湾北岸6种沿海防护林冠层结构及林下光环境特征。结果表明：6种林分以中山杉Taxodium ascendens × mucronatum间隙分数最大，红叶椿Ailanthus altissima ‘Hongye’，洋白蜡Fraxinus pennsylvanica和美国皂荚Gleditsia triacanthos的平均间隙分数接近，乌桕Sapium sebiferum和女贞Ligustrum lucidum的平均间隙分数相对较小。而各林分叶面积指数特征与间隙分数相反，女贞和乌桕平均叶面积指数（LAI）较高，红叶椿、洋白蜡、美国皂荚和中山杉的叶面积指数接近。红叶椿叶丛生效应较低，而美国皂荚、乌桕、中山杉、洋白蜡和女贞具有类似的丛生效应。各林分内光量子通量密度（PPFD）具有较大差异，其大小依次为中山杉＞美国皂荚＞红叶椿，洋白蜡＞乌桕＞女贞。图2表4参18

Understory light environment and canopy structure of six coastal protection forests on the north coast of Hangzhou Bay

The canopy structure and environmental characteristics from understory light for six coastal protection forest stands （Taxodium ascendens × mucronatum,Ailanthus altissima ＇Hongye＇,Fraxinus pennsylvanica,Gleditsia triacanthos,Sapium sebiferum,and Ligustrum lucidum） on the north coast of Hangzhou Bay were measured by Tracing Radiation and Canopy Architecture （TRAC）.Results showed that the canopy gap fraction of the T.ascendens × mucronatum stand was greater than the other five stands which had no major difference between them.The stand leaf area index （LAI） was opposite of the gap fraction with the average LAI of S.sebiferum and L.lucidum significantly （P0.05）higher than the other stands with the other four stands being about the same.Leaf clumping was significantly （P0.05）lower for the A.altissima ＇Hongye＇ stand with the other five stands about the same.Understory photosynthetic photon flux density （PPFD） for the six stands had significantly （P0.05） differences with the order of light intensity as：T.ascendens ×mucronatum G.triacanthos A.altissima ＇Hongye＇,F.pennsylvanica S.sebiferum L.lucidum.