Leaf phenological shifts and plant–microbe–soil interactions can determine forest productivity and nutrient cycling under climate change in an ecosystem model

Climate change is expected to affect tree leaf phenology by extending the length of the growing season (LGS), which will affect the productivity and nutrient cycling of forests. Interactions between plants and microbes will mediate the ecosystem processes further through microbe-mediated plant–soil feedback (PSF). To investigate the possible consequences of interactions between the extension of the growing season (GS) and PSF under various conditions, we developed a simple theoretical model (LGS-PSF model). The LGS-PSF model predicts that microbe-mediated PSF will intensify the negative effects of increasing temperature on the size of soil carbon stock when compared with simulations without the PSF effect. The combined effects of increasing temperature and PSF on the size of soil carbon stock occurs through enhanced activity of individual microbes and increased microbial population size. More importantly, the model also demonstrated that a longer GS mitigates this negative effect on carbon accumulation in soil, not through increased net primary production, but through intensified competition for nutrients between plants and microbes, thus suppressing microbial population growth. Our model suggested that the interactive effects of the LGS and PSF on carbon and nitrogen dynamics in forests should be incorporated into larger scale quantitative models for better forecasting of future forest functions under climate change. © 2016, The Ecological Society of Japan.