Centre for Biogeochemistry in the Anthropocene, University of Oslo, Oslo 0316, Norway; Department of Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam 1081 HV, the Netherlands.
Department of Environmental Systems Science, ETH Zurich, Zurich 8092, Switzerland.
Sci Total Environ. 2022 Sep 15;839:156326. doi: 10.1016/j.scitotenv.2022.156326. Epub 2022 May 30.
Net Ecosystem Production (NEP) of forests is the net carbon dioxide (CO) fluxes between land and the atmosphere due to forests' biogeochemical processes. NEP varies with natural drivers such as precipitation, air temperature, solar radiation, plant functional type (PFT), and soil texture, which affect the gross primary production and ecosystem respiration, and thus the net C sequestration. It is also known that deposition of sulphur and nitrogen influences NEP in forest ecosystems. These drivers' respective, unique effects on NEP, however, are often difficult to be individually identified by conventional bivariate analysis. Here we show that by analyzing 22 forest sites with 231 site-year data acquired from FLUXNET database across Europe for the years 2000-2014, the individual, unique effects of these drivers on annual forest CO fluxes can be disentangled using Generalized Additive Models (GAM) for nonlinear regression analysis. We show that S and N deposition have substantial impacts on NEP, where S deposition above 5 kg S ha yr can significantly reduce NEP, and N deposition around 22 kg N ha yr has the highest positive effect on NEP. Our results suggest that air quality management of S and N is crucial for maintaining healthy biogeochemical functions of forests to mitigate climate change. Furthermore, the empirical models we developed for estimating NEP of forests can serve as a forest management tool in the context of climate change mitigation. Potential applications include the assessment of forest carbon fluxes in the REDD+ framework of the UNFCCC.
森林净生态系统生产力（NEP）是指由于森林的生物地球化学过程，陆地与大气之间的二氧化碳（CO）净通量。NEP 随降水、空气温度、太阳辐射、植物功能型（PFT）和土壤质地等自然驱动因素而变化，这些因素影响总初级生产力和生态系统呼吸，从而影响净碳封存。此外，硫和氮的沉积也会影响森林生态系统的 NEP。然而，这些驱动因素对 NEP 的各自独特影响通常很难通过常规的二元分析来单独识别。在这里，我们通过分析来自欧洲 FLUXNET 数据库的 22 个森林站点 2000-2014 年的 231 个站点年数据（共 22 个森林站点，231 个站点年数据），表明通过使用广义加性模型（GAM）进行非线性回归分析，可以分离这些驱动因素对年度森林 CO 通量的单独、独特影响。我们表明，S 和 N 的沉积对 NEP 有显著影响，S 的沉积超过 5 kg S ha yr 可以显著降低 NEP，而 N 的沉积在 22 kg N ha yr 左右对 NEP 有最高的正效应。我们的研究结果表明，对 S 和 N 的空气质量管理对于维持森林健康的生物地球化学功能以减缓气候变化至关重要。此外，我们为估计森林 NEP 而开发的经验模型可以作为气候变化缓解背景下的森林管理工具。潜在的应用包括在《联合国气候变化框架公约》的 REDD+框架下评估森林碳通量。
