Abstract Interannual variability (IAV) in ecosystem productivity may reveal vulnerabilities of vegetation to climate stressors. We analyzed IAV of northern hemisphere ecosystems using several remote sensing datasets, including longstanding observations of the normalized difference vegetation index (NDVI) and more novel metrics for productivity including solar-induced chlorophyll fluorescence (SIF) and the near-infrared reflectance of vegetation (NIRv). Although previous studies have suggested SIF better tracks variations in ecosystem productivity at seasonal timescales, we found that satellite datasets (including SIF) and eddy covariance flux tower observations were subject to significant uncertainty when assessing IAV at fine spatial scales. Even when observations were aggregated regionally, IAV in productivity estimated by the various satellite products were not always well correlated. In response to these inconsistencies, we applied a statistical method on regionally aggregated productivity data in four selected North American ecoregions and identified two dominant modes of IAV—seasonal redistribution and amplification—that were consistent across satellite datasets. The seasonal redistribution mode, which played a stronger role at lower latitudes, associated high (low) spring productivity with warm (cold) spring and summer temperatures, but also with lower (higher) productivity and water availability in summer and fall, indicating that enhanced growth in spring may contribute to an earlier depletion of water resources. The amplification mode associated an increase (decrease) in productivity across the growing season with above-average (below-average) summer moisture conditions. Even though our statistical analysis at large spatial scales revealed meaningful links between terrestrial productivity and climate drivers, our analysis does suggest that IAV and long-term trends in presently available novel and more established satellite observations must be interpreted cautiously, with careful attention to the spatial scales at which a robust signal emerges.

中文翻译：

---

卫星观测揭示了北方生态系统生产力的季节性重新分布以响应年际气候变化

摘要 生态系统生产力的年际变率 (IAV) 可能揭示植被对气候压力因素的脆弱性。我们使用几个遥感数据集分析了北半球生态系统的 IAV，包括对标准化差异植被指数 (NDVI) 的长期观察和更多新的生产力指标，包括太阳诱导的叶绿素荧光 (SIF) 和植被的近红外反射率 (NIRv) ）。尽管之前的研究表明 SIF 可以更好地跟踪季节性时间尺度上生态系统生产力的变化，但我们发现，在精细空间尺度上评估 IAV 时，卫星数据集（包括 SIF）和涡流协方差通量塔观测值存在重大不确定性。即使将观察结果按区域汇总，各种卫星产品估计的 IAV 生产率并不总是很好地相关。为了应对这些不一致，我们对四个选定的北美生态区的区域汇总生产力数据应用了一种统计方法，并确定了 IAV 的两种主要模式——季节性再分配和放大——它们在卫星数据集中是一致的。在低纬度地区发挥更大作用的季节性再分配模式将高（低）的春季生产力与温暖（冷）的春夏季温度联系起来，但也与夏季和秋季较低（较高）的生产力和可用水量有关，表明春季的生长可能会导致水资源较早枯竭。放大模式与高于平均水平（低于平均水平）的夏季水分条件与整个生长季节的生产力增加（减少）相关。尽管我们在大空间尺度上的统计分析揭示了陆地生产力和气候驱动因素之间有意义的联系，但我们的分析确实表明，必须谨慎解释 IAV 和目前可用的新的和更成熟的卫星观测的长期趋势，并仔细注意空间出现稳健信号的尺度。