Leaf Area Index Data, South-East Queensland Peri-urban SuperSite, Samford, Core 1 ha, 2014

Canopy leaf area index data were collected by David Tucker using digital cover photography (DCP) for the South East Queensland Peri-urban SuperSite Samford. Nine transects were established within the one hectare plot. A Nikon D5200 single-lens reflex camera and AF-S DX Nikkor 18-55 mmf/3.5-5.6G VR lens was used for recording all images. Camera settings Included ISO200, f8.0, exposure -1.0 and RAW format. Leaf area index (LAI) can be defined as the total one sided area of leaf tissue per unit area of ground and is a key derived parameter that is associated with water and light interception, radiation transfer, water and carbon exchange (Bréda, 2003). Canopy cover can be defined as the fraction of ground shaded by the vertical projection of tree crowns (Walker et al. 1981). These measures may be used as proxies for actual canopy leaf area. Leaf area index is the preferred measure of cover for vegetation and as a key variable used in total biomass estimation and in carbon cycling prediction models. Indirect measures of LAI include digital photographic methods using flat or hemispherical images, referred to respectively as DCP (digital cover photography) and DHP (digital hemispheric photography). LAI measurements are carried out at each SuperSite using the most appropriate method for the vegetation type present. Digital Cover Photography (DCP) is recommended for medium stature (10-40 m) vegetation with simple structure. DCP was originally developed for sparse to moderately dense broadleaf forest and has also been tested in sparse savanna woodland. DCP is recommended for these vegetation types and has also been suggested for more dense forests (Pekin and MacFarlane 2009). Digital Hemispheric Photography (DHP) is recommended for short vegetation (4-8 m) e.g. low banksia woodland, complex (multi strata) and tall vegetation (> 40+ m) using images taken 20 m apart (MacFarlane et al. 2007).

本数据集的冠层叶面积指数数据由David Tucker采用数码覆盖摄影（Digital Cover Photography, DCP）技术，针对昆士兰州东南部城郊Samford超级样地采集所得。该样地面积为1公顷，共设置9条样带。所有影像均采用尼康D5200单反相机搭配AF-S DX 尼克尔18-55mm f/3.5-5.6G VR镜头拍摄，相机参数设置为：ISO感光度200、光圈f/8.0、曝光补偿-1.0，且采用RAW格式存储。叶面积指数（Leaf Area Index, LAI）可定义为单位地面面积上植物叶片组织的单侧总表面积，是关联水分与光截获、辐射传输、水碳交换的关键衍生参数（Bréda, 2003）。冠层覆盖度则可定义为树木树冠垂直投影所遮蔽的地面面积占比（Walker等, 1981）。上述两类指标均可作为实际冠层叶面积的替代表征。叶面积指数是植被覆盖度评估的首选指标，同时也是总生物量估算及碳循环预测模型中的核心变量。叶面积指数的间接测定方法包括采用平拍或半球面影像的数码摄影技术，二者分别对应数码覆盖摄影（DCP）与数码半球摄影（Digital Hemispheric Photography, DHP）。各超级样地均会根据所在区域的植被类型，选用最适配的方法开展叶面积指数测定工作。其中数码覆盖摄影（DCP）适用于结构简单、株高10~40米的中等体型植被，该技术最初针对稀疏至中等密度的阔叶林开发，后续亦在稀树萨瓦纳林地中开展过测试，其适用于上述植被类型，同时也被推荐应用于密度更高的森林（Pekin与MacFarlane, 2009）。数码半球摄影（DHP）则适用于株高4~8米的低矮植被（如低矮班克木林地）、结构复杂的多层植被，以及株高超过40米的高大植被，该方法要求影像拍摄间隔为20米（MacFarlane等, 2007）。