Rapid shrub expansion has been observed across the Arctic, driving a need for regional-scale estimates of shrub biomass and shrub-mediated ecosystem processes such as rainfall interception. Synthetic-Aperture Radar (SAR) data have been shown sensitive to vegetation canopy characteristics across many ecosystems, thereby potentially providing an accurate and cost-effective tool to quantify shrub canopy cover. This study evaluated the sensitivity of L-band Advanced Land Observing Satellite 2 (ALOS-2) data to the aboveground biomass and Leaf Area Index (LAI) of dwarf birch and alder in the Trail Valley Creek watershed, Northwest Territories, Canada. The σ°_VH /σ°_VV ratio showed strong sensitivity to both LAI (R² = 0.72 with respect to in-situ measurements) and wet aboveground biomass (R² = 0.63) of dwarf birch. Our ALOS-2-derived maps revealed high variability of birch shrub LAI and biomass across spatial scales. The LAI map was fed into the sparse Gash model to estimate shrub rainfall interception, an important but under-studied component of the Arctic water balance. Results suggest that on average across the watershed, 17 ± 3% of incoming rainfall was intercepted by dwarf birch (during summer 2018), highlighting the importance of shrub rainfall interception for the regional water balance. These findings demonstrate the unexploited potential of L-band SAR observations from satellites for quantifying the impact of shrub expansion on Arctic ecosystem processes.

已经观察到整个北极地区的灌木迅速扩张，这推动了对灌木生物量和灌木介导的生态系统过程（如降雨拦截）进行区域规模估计的需求。合成孔径雷达 (SAR) 数据已被证明对许多生态系统中的植被冠层特征很敏感，因此有可能提供一种准确且具有成本效益的工具来量化灌木冠层覆盖。本研究评估了 L 波段高级陆地观测卫星 2 (ALOS-2) 数据对加拿大西北地区 Trail Valley Creek 流域中矮桦树和桤木的地上生物量和叶面积指数 (LAI) 的敏感性。σ° _VH /σ° _VV比值对两种 LAI 都表现出很强的敏感性（R ²  = 0.72 就原位测量）和 矮桦树的湿地上生物量（R ² = 0.63）。我们的 ALOS-2 衍生地图揭示了桦树灌木 LAI 和生物量在空间尺度上的高度可变性。LAI 地图被输入稀疏 Gash 模型以估计灌木降雨截获量，这是北极水平衡的一个重要但研究不足的组成部分。结果表明，平均而言，整个流域有 17 ± 3% 的降雨被矮桦树拦截（2018 年夏季），突出了灌木降雨拦截对区域水平衡的重要性。这些发现表明，卫星 L 波段 SAR 观测在量化灌木扩张对北极生态系统过程的影响方面具有未开发的潜力。