Goedkoop Willem, Adler Sven, Huser Brian, Gardfjell Hans, Lau Danny C P
Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
Glob Chang Biol. 2025 Jul;31(7):e70314. doi: 10.1111/gcb.70314.
We combined decadal data (23-35 y) on nutrient concentrations for nine subarctic lakes with satellite imagery of vegetation (NDVI) to link the ongoing nutrient declines to the climate change-induced greening of landscapes. Total phosphorus water concentrations (Total-P) showed declining trends for all nine lakes, ranging from 1.5%-3.6%/y over the last decades. For most of the lakes' drainage areas, NDVI showed a dramatic increase during the 1990s and leveled off between 2001 and 2020. P sequestration in the lakes' drainage areas generally increased by 12%-30% between 1983-1994 and 2001-2020, with an exception of one high-elevation lake for which P sequestration more than doubled. Area-specific P-sequestration estimates for 1983-1994 averaged 1.04 ± 0.10 tons P/km among all lakes but increased by 12%-33% for eight of the nine lakes during 2001-2020. Similar trends were found for nitrogen (N) sequestration, although these were an order of magnitude higher. These estimates illustrate long-term changes in the sequestration of N and P by terrestrial vegetation in the region. Total-P and DIN water concentrations showed negative correlations with both the NDVI of their drainage areas and plot-scale measurements of tundra dwarf shrub cover. These correlations explained 51.8%-75.4% of the variability in declining nutrient water concentrations and showed the strong links between terrestrial vegetation development and declines in nutrient inputs to downstream lakes. Similar processes are likely ongoing in other parts of the Arctic where vegetation development is progressing, but are either not detected due to the lack of long-term monitoring data or compensated for by nutrients released from thawing permafrost and/or thermokarst slumps. Upscaling our P- and N-sequestration estimates for the nine lakes to the entire Arctic/alpine ecoregion in Sweden showed an average increase of 12.0 ± 1.7 Mtons P and 122.6 ± 17.5 Mtons N between the periods 1982-1994 and 2001-2020.
我们将9个亚北极湖泊的年代际数据（23 - 35年）中的营养物质浓度与植被卫星图像（归一化植被指数，NDVI）相结合，以将当前营养物质的减少与气候变化导致的景观绿化联系起来。所有9个湖泊的总磷水浓度（总磷）均呈下降趋势，在过去几十年中，下降幅度为每年1.5% - 3.6%。在大多数湖泊的流域，NDVI在20世纪90年代显著增加，并在2001年至2020年期间趋于平稳。1983 - 1994年至2001 - 2020年期间，湖泊流域的磷固存总体增加了12% - 30%，但有一个高海拔湖泊除外，其磷固存增加了一倍多。1983 - 1994年所有湖泊的单位面积磷固存估计平均为1.04±0.10吨磷/平方公里，但在2001 - 2020年期间，9个湖泊中有8个湖泊的单位面积磷固存增加了12% - 33%。氮（N）固存也发现了类似趋势，尽管其数量级更高。这些估计说明了该地区陆地植被对氮和磷固存的长期变化。总磷和溶解性无机氮水浓度与它们流域的NDVI以及苔原矮灌木覆盖的样地尺度测量值均呈负相关。这些相关性解释了营养物质水浓度下降变化的51.8% - 75.4%，并表明陆地植被发育与下游湖泊营养物质输入减少之间存在紧密联系。在北极其他植被正在发展的地区，可能也在进行类似的过程，但由于缺乏长期监测数据而未被检测到，或者被永久冻土融化和/或热喀斯特塌陷释放的营养物质所抵消。将我们对9个湖泊的磷和氮固存估计扩大到瑞典整个北极/高山生态区，结果显示在1982 - 1994年至2001 - 2020年期间，平均磷增加了12.0±1.7百万吨，氮增加了122.6±17.5百万吨。
