Patterns of canopy and surface layer consumption in a boreal forest fire from repeat airborne lidar
Patterns of canopy and surface layer consumption in a boreal forest fire from repeat airborne lidar
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DOI：
10.1088/1748-9326/aa6ade
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发表时间：
2017-06-01
影响因子：
6.7
通讯作者：
Pattison, Robert
中科院分区：
文献类型：
--
作者：
Alonzo, Michael;Morton, Douglas C.;Pattison, Robert
在寒带地区，火灾是森林干扰的主要动因，对生态系统结构、碳循环和全球气候产生直接影响。全球和生物群系尺度的影响由燃烧严重程度介导，以森林冠层损失和土壤有机层消耗来衡量。迄今为止，对烧伤严重程度的空间变异性的了解仅限于稀疏的野外采样和中等分辨率的卫星数据。本研究利用2005年阿拉斯加基奈半岛北部森林火灾前后的机载激光雷达数据，直接估算了林冠垂直结构和地表高程的变化。研究发现，林冠和地表损失与火灾前的物种组成密切相关，并在亚30m分辨率下表现出重要的细尺度空间变异性。林冠体积减少分数从低地黑云杉林的0.61到白云杉阔叶林的0.27不等。剩余结构在很大程度上反映了直立枯死的树木，突出了火灾前森林结构对地上生物量延迟碳损失、火灾后反照率和林下光照环境变率的影响。地表高程损失中值在低地黑云杉林分中最高（0.18 m），而在混交林中低得多（0.02 m），这与火灾前有机层积累的差异一致。重复激光雷达测量的空间连续燃烧深度估计为限制地表有机层的碳排放提供了新的信息，并可能为火灾后连续轨迹的相关研究提供信息。来自Landsat的燃烧严重程度光谱测量值与黑云杉林分的冠层（r = 0.76）和地表（r = -0.71）去除相关，但在混合林分中捕获的火灾效应空间变异性较少（冠层r = 0.56，地表r = -0.26），这强调了使用来自Landsat的燃烧严重程度替代测量值来捕捉异质性北方森林景观中火灾效应的困难。
Fire in the boreal region is the dominant agent of forest disturbance with direct impacts on ecosystem structure, carbon cycling, and global climate. Global and biome-scale impacts are mediated by burn severity, measured as loss of forest canopy and consumption of the soil organic layer. To date, knowledge of the spatial variability in burn severity has been limited by sparse field sampling and moderate resolution satellite data. Here, we used pre- and post-fire airborne lidar data to directly estimate changes in canopy vertical structure and surface elevation for a 2005 boreal forest fire on Alaska's Kenai Peninsula. We found that both canopy and surface losses were strongly linked to pre-fire species composition and exhibited important fine-scale spatial variability at sub-30m resolution. The fractional reduction in canopy volume ranged from 0.61 in lowland black spruce stands to 0.27 in mixed white spruce and broadleaf forest. Residual structure largely reflects standing dead trees, highlighting the influence of pre-fire forest structure on delayed carbon losses from aboveground biomass, post-fire albedo, and variability in understory light environments. Median loss of surface elevation was highest in lowland black spruce stands (0.18 m) but much lower in mixed stands (0.02 m), consistent with differences in pre-fire organic layer accumulation. Spatially continuous depth-of-burn estimates from repeat lidar measurements provide novel information to constrain carbon emissions from the surface organic layer and may inform related research on post-fire successional trajectories. Spectral measures of burn severity from Landsat were correlated with canopy (r = 0.76) and surface (r = -0.71) removal in black spruce stands but captured less of the spatial variability in fire effects for mixed stands (canopy r = 0.56, surface r = -0.26), underscoring the difficulty in capturing fire effects in heterogeneous boreal forest landscapes using proxy measures of burn severity from Landsat.