edu.ucar.opensky::articles:27194 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-24T18:50:00.324473 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7qv3rqx Phenology of photosynthesis in winter-dormant temperate and boreal forests: Long-term observations from flux towers and quantitative evaluation of phenology models 2024-05-01T00:00:00Z publication https://n2t.org/ark:/85065/d7qv3rqx https://doi.org/10.1029/2023JG007839 Bowling, D. R. author Schädel, C. author Smith, K. R. author Richardson, A. D. author Bahn, M. author Arain, M. A. author Varlagin, A. author Ouimette, A. P. author Frank, J. M. author Barr, A. G. author Mammarella, I. author Šigut, L. author Foord, V. author Burns, Sean author Montagnani, L. author Litvak, M. E. author Munger, J. W. author Ikawa, H. author Hollinger, D. Y. author Blanken, P. D. author Ueyama, M. author Matteucci, G. author Bernhofer, C. author Bohrer, G. author Iwata, H. author Ibrom, A. author Pilegaard, K. author Spittlehouse, D. L. author Kobayashi, H. author Desai, A. R. author Staebler, R. M. author Black, T. A. author UCAR/NCAR - Library publisher We examined the seasonality of photosynthesis in 46 evergreen needleleaf (evergreen needleleaf forests (ENF)) and deciduous broadleaf (deciduous broadleaf forests (DBF)) forests across North America and Eurasia. We quantified the onset and end (StartGPP and EndGPP) of photosynthesis in spring and autumn based on the response of net ecosystem exchange of CO2 to sunlight. To test the hypothesis that snowmelt is required for photosynthesis to begin, these were compared with end of snowmelt derived from soil temperature. ENF forests achieved 10% of summer photosynthetic capacity similar to 3 weeks before end of snowmelt, while DBF forests achieved that capacity similar to 4 weeks afterward. DBF forests increased photosynthetic capacity in spring faster (1.95% d-1) than ENF (1.10% d-1), and their active season length (EndGPP-StartGPP) was similar to 50 days shorter. We hypothesized that warming has influenced timing of the photosynthesis season. We found minimal evidence for long-term change in StartGPP, EndGPP, or air temperature, but their interannual anomalies were significantly correlated. Warmer weather was associated with earlier StartGPP (1.3-2.5 days degrees C-1) or later EndGPP (1.5-1.8 days degrees C-1, depending on forest type and month). Finally, we tested whether existing phenological models could predict StartGPP and EndGPP. For ENF forests, air temperature- and daylength-based models provided best predictions for StartGPP, while a chilling-degree-day model was best for EndGPP. The root mean square errors (RMSE) between predicted and observed StartGPP and EndGPP were 11.7 and 11.3 days, respectively. For DBF forests, temperature- and daylength-based models yielded the best results (RMSE 6.3 and 10.5 days). UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. None eng geoscientificInformation