气候变化领域集成服务门户(CCPortal): Characterizing light across a strip shelterwood in a mixed conifer forest

CCPortal

DOI	10.1016/j.foreco.2019.05.015
	Characterizing light across a strip shelterwood in a mixed conifer forest
	Hossain K.L.; Comeau P.G.
发表日期	2019
ISSN	0378-1127
起始页码	134
结束页码	145
卷号	445
英文摘要	A knowledge of how light varies within gaps is fundamental to understanding variation in survival and growth of regenerating trees. Simple indices based on a small number of instantaneous measurements by portable sensors or cameras are widely used for this purpose. But the effectiveness of these indices for estimating growing season transmittance is influenced by stand characteristics and local weather conditions. This study was conducted in two small (50 m × 150 m)clearings in a mixed stand of the interior cedar hemlock zone of southern British Columbia to evaluate several commonly used light estimation techniques, including: (1)hemispherical photography; (2)LAI-2000 plant canopy analyzer; and, (3)midday measurements of % photosynthetic photon flux density (hourly average PPFD)under sunny and overcast skies in a strip-shelterwood system. While diffuse indices from hemispherical methods (LAI-2000 and photograph)performed poorly, their direct and total indices (photograph)gave lower variability (lower rmse)and stronger correlations (higher r2)with growing season transmittance. Sky conditions under which light measurements were recorded by photosynthetically active radiation (PAR)sensors influenced the relationships between PAR sensor indices and growing season transmittance. For example, measuring light around midday on a sunny day provided stronger correlation with growing season transmittance than overcast day measurements. Moreover, rather than using one midday light measurement on a sunny or an overcast day, an average of two measurements increased r2 and reduced bias while measuring light three times on a sunny day (morning, noon and afternoon)gave the highest r2 and the lowest variability. Several indices also correlated strongly with monthly light levels, measured from May – September. Based on the finding that indices that accounted for direct beam contribution gave the best outcomes, we suggest that canopy conditions (degree of heterogeneity), stand orientation and gap sizes should be considered in selecting an instantaneous light index for studies in high latitude forests. © 2019 Elsevier B.V.
英文关键词	Hemispherical photography; LAI-2000 Plant Canopy Analyzer; Light transmittance; Strip shelterwood
语种	英语
scopus关键词	Light measurement; Photography; Plants (botany); Reforestation; Hemispherical photography; Instantaneous measurement; Light transmittance; Local weather conditions; Photosynthetic photon flux densities; Photosynthetically active radiation; Plant canopies; Strip shelterwood; Image analysis; canopy architecture; climate conditions; coniferous forest; estimation method; growing season; growth; light effect; mixed forest; photography; photon flux density; regeneration; shelterbelt; stand structure; survival; transmittance; Growing Season; Image Analysis; Light; Photography; Reforestation; Shelterwood; Strips; Transmittance; British Columbia; Canada; Coniferophyta
来源期刊	Forest Ecology and Management
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/155955
作者单位	University of Alberta, Renewable Resources, 751 General Services Building, Edmonton, Alberta T6G 2H1, Canada
推荐引用方式 GB/T 7714	Hossain K.L.,Comeau P.G.. Characterizing light across a strip shelterwood in a mixed conifer forest[J],2019,445.
APA	Hossain K.L.,&Comeau P.G..(2019).Characterizing light across a strip shelterwood in a mixed conifer forest.Forest Ecology and Management,445.
MLA	Hossain K.L.,et al."Characterizing light across a strip shelterwood in a mixed conifer forest".Forest Ecology and Management 445(2019).