Speaker
Description
Abstract
Forests play a crucial role in regulating the global carbon cycle and mitigating climate change by acting as major terrestrial carbon sinks. However, rising atmospheric CO₂ concentrations, increasing temperatures, more frequent drought events, and nutrient enrichment through fertilization and nitrogen deposition are simultaneously altering forest productivity and carbon cycling. Although numerous studies have examined the individual effects of these drivers, comprehensive cross-scale assessments of their interactions in forest ecosystems are limited. We conducted a global synthesis to evaluate the combined effects of climate change drivers and nutrient availability across different organizational levels, while accounting for nutrient types, forest age, nutrient types, climatic zones, and broad tree taxonomic groups. Our synthesis revealed that elevated CO₂ and nutrient availability synergistically enhance above- and belowground productivity, particularly in young forests, most likely by enhancing the photosynthate production and structural development. In contrast, warming appears most beneficial (or least detrimental) under low soil nutrient availability across physiological, productivity, and carbon-pool responses due to enhanced transpiration, nutrient mineralization (more leaching), and heat stress. Nevertheless, warming and nutrient interaction stimulated soil respiration in forests, indicating accelerated carbon turnover. Despite that high availability of N improves water use efficiency (as is the case for base cations), at stand scale interactive effects of water deficit with N and also P are often neutral or even negative, indicating increased drought vulnerability under high nutrient availability, e.g. of biomass production. Collectively, our findings suggest that while nutrient enrichment may enhance forest productivity under elevated CO₂, it is likely to be increasingly offset by warming- and drought-induced stresses. Consequently, nutrient addition alone is unlikely to mitigate future climate-change impacts on forests and may accelerate carbon loss.
Keywords: Climate change; Forest ecosystems; Meta-analysis; Carbon cycle
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