de Wit Heleen A, Stoddard John L, Monteith Donald T, Sample James E, Austnes Kari, Couture Suzanne, Fölster Jens, Higgins Scott N, Houle Daniel, Hruška Jakub, Krám Pavel, Kopacek Jiří, Paterson Andrew M, Valinia Salar, Van Dam Herman, Vuorenmaa Jussi, Evans Chris D
Norwegian Institute for Water Research, N-0349 Oslo, Norway.
Centre for Biogeochemistry in the Anthropocene, University of Oslo, N-0315 Oslo, Norway.
Environ Res Lett. 2021 Sep 21;16(10):1-13. doi: 10.1088/1748-9326/ac2526.
Surface water browning, the result of increasing concentrations of dissolved organic matter (DOM), has been widespread in northern ecosystems in recent decades. Here, we assess a database of 426 undisturbed headwater lakes and streams in Europe and North America for evidence of trends in DOM between 1990 and 2016. We describe contrasting changes in DOM trends in Europe (decelerating) and North America (accelerating), which are consistent with organic matter solubility responses to declines in sulfate deposition. While earlier trends (1990-2004) were almost entirely related to changes in atmospheric chemistry, climatic and chemical drivers were equally important in explaining recent DOM trends (2002-2016). We estimate that riverine DOM export from northern ecosystems increased by 27% during the study period. Increased summer precipitation strengthened upward dissolved organic carbon trends while warming apparently damped browning. Our results suggest strong but changing influences of air quality and climate on the terrestrial carbon cycle, and on the magnitude of carbon export from land to water.
地表水褐变是溶解有机物（DOM）浓度增加的结果，近几十年来在北方生态系统中广泛存在。在此，我们评估了欧洲和北美的426个未受干扰的源头湖泊和溪流的数据库，以寻找1990年至2016年期间DOM趋势的证据。我们描述了欧洲（减速）和北美（加速）DOM趋势的对比变化，这与有机物溶解度对硫酸盐沉积下降的反应一致。虽然早期趋势（1990 - 2004年）几乎完全与大气化学变化有关，但气候和化学驱动因素在解释近期DOM趋势（2002 - 2016年）方面同样重要。我们估计，在研究期间，北方生态系统的河流DOM输出增加了27%。夏季降水增加加强了溶解有机碳上升趋势，而变暖显然抑制了褐变。我们的结果表明，空气质量和气候对陆地碳循环以及从陆地到水体的碳输出量有强烈但不断变化的影响。
