LAUSR

Climate warming is expected to lengthen growing seasons of temperate forest ecosystems and increase gross primary productivity. Simultaneously, warming is expected to increase summer ecosystem respiration, which could offset gains accrued from longer growing seasons. These responses have been observed during anomalously warm years, but the role of future climate change on phenological tradeoffs and how they affect net primary productivity (NPP) at regional scales in temperate forests remains unexplored. We simulated scenarios of climate change on monthly forest NPP throughout 18 million hectares of temperate forests in New England, USA through year 2100. Using an ecophysiological model coupled to a forest landscape model, we simulated scenarios of climate change on monthly NPP. A high emission scenario (RCP 8.5), resulted in longer growing seasons that offset mid-summer ecosystem respiration costs and produced greater annual NPP throughout the study landscape compared to simulations using the current climate. In spring and autumn months, temperature was positively associated with greater NPP; in summer months, the relationship was negative. Spatially, the greatest increase in NPP occurred in the warmer southern region under a warm climate scenario with increased precipitation. Under a warm scenario with drier conditions, the greatest increase in NPP occurred in the cooler northern region. Phenological tradeoffs will affect NPP 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 increases in NPP throughout the temperate forests of New England in the future.