Spatial quantification of leafless canopy structure in a boreal birch forest
Spatial quantification of leafless canopy structure in a boreal birch forest
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DOI：
10.1016/j.agrformet.2013.12.005
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发表时间：
2014-05
影响因子：
6.2
通讯作者：
T. Reid;Michael S. Spencer;B. Huntley;S. Hancock;R. Essery;J. Carle;R. Holden;R. Baxter;N. Rutter
中科院分区：
文献类型：
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作者：
T. Reid;Michael S. Spencer;B. Huntley;S. Hancock;R. Essery;J. Carle;R. Holden;R. Baxter;N. Rutter
北方地区的落叶冠层影响融雪能量，降低冬季地表反照率，从而对天气和气候产生强烈影响。在这项工作中，2011年3月和2012年3月，在瑞典北部山区桦林地区的38个地点收集了无叶冠层结构的地面测量数据，包括半球形摄影、地面激光扫描（TLS）和人工树木调查。照片衍生的天空视图分数与照片站点周围5 m半径内的树木基底面积呈显著负相关（r< - 0.9）。为了将研究结果扩展到更广泛的区域，从2005年夏季收集的机载激光雷达（ALS）数据中获得了5公里× 3公里区域的冠层高度图。利用TLS获得的冠层高度验证ALS估算值，并建立了简单的模型来建立半球天空视图与ALS冠层高度之间的关系（RMSE < 5%）。尽管ALS分辨率相对较低（~ 1返回m−2），但模型和ALS数据为估算大面积桦林的冠层辐射转移和生物量提供了有用的方法。
Leafless deciduous canopies in boreal regions affect the energy available for snowmelt and reduce overall surface albedo during winter, thereby exerting a strong influence on weather and climate. In this work, ground-based measurements of leafless canopy structure, including hemispherical photography, terrestrial laser scanning (TLS) and manual tree surveys were collected at 38 sites in an area of mountain birch forest in northern Sweden in March 2011 and 2012. Photo-derived sky view fraction was strongly inversely correlated (r< −0.9) to the total tree basal area in a 5 m radius around the photo site. To expand findings to wider areas, maps of canopy height for a 5 km × 3 km area were obtained from airborne lidar (ALS) data collected during summer 2005. Canopy heights derived from TLS were used to validate the ALS estimates, and simple models were developed to establish relationships between hemispherical sky view and ALS canopy height (RMSE < 5%). The models and ALS data provide useful methods for estimating canopy radiative transfer and biomass over wide areas of birch forest, despite the relatively low ALS resolution (∼1 return m−2).