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Harvard Forest Symposium Abstract 2017

  • Title: Effects of climate change on forest phenological tradeoffs: Will a conceptual representation of seasonal productivity hold up under a high emissions future?
  • Primary Author: Matthew Duveneck (Harvard Forest)
  • Additional Authors: Jonathan Thompson (Harvard Forest)
  • Abstract:

    Climate warming is expected to lengthen the growing season of temperate forest ecosystems and increase gross primary productivity. Simultaneously, climate warming is expected to increase summer respiration demands, which may offset gains accrued from longer growing seasons. The spatial and temporal impact of net primary productivity (NPP) under climate change remains uncertain. Evidence based on anomalous warm years observed at eddy-covariance flux sites suggests that earlier growth in the spring will offset losses due to increased mid-summer respiration. The warming observed in these years, however, does not come close to approximating the magnitude of warming that is anticipated based on projections for the coming century. Using a previously calibrated and validated ecophysiological model coupled to a forest landscape model, we simulated scenarios of climate change and elevated CO2 on monthly NPP throughout 18 m hectares of temperate forests in New England, USA from 2010 to 2100. We found that under a high emission future (RCP 8.5), earlier and longer growing seasons outweighed mid-summer respiration costs and increased annual NPP throughout the study landscape compared to simulations using the current climate. In simulation year 2100, the largest changes in monthly NPP occurred in April, a month when forests have been historically limited by cooler temperatures. In spring and autumn months, temperature was positively associated with greater growth, but in summer months, the relationship became negative. Spatially, the greatest increase in NPP occurred in the central and southern region of New England where mid-summer respiration costs were low. These results highlight phenological tradeoffs that will affect the productivity of future forests and their potential to serve as a negative feedback to climate change. Barring other limitations, longer growing seasons will offset greater respiratory demands and contribute to large increases in NPP in the temperate mesic forest of in New England.

  • Research Category: Forest-Atmosphere Exchange; Ecological Informatics and Modelling