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biomass production, biomass production efficiency, carbon allocation, global forest database, nutrients, photosynthesis, root symbionts
Abstract:
Trees with sufficient nutrition are known to allocate carbon preferentially to aboveground plant parts. Our
global study of 49 forests revealed an even more fundamental carbon allocation response to nutrient
availability: forests with high-nutrient availability use 58 ± 3% (mean ± SE; 17 forests) of their photosynthates
for plant biomass production (BP), while forests with low-nutrient availability only convert 42 ± 2%
(mean ± SE; 19 forests) of annual photosynthates to biomass. This nutrient effect largely overshadows
previously observed differences in carbon allocation patterns among climate zones, forest types and age classes.
If forests with low-nutrient availability use 16 ± 4% less of their photosynthates for plant growth, what are
these used for? Current knowledge suggests that lower BP per unit photosynthesis in forests with low- versus
forests with high-nutrient availability reflects not merely an increase in plant respiration, but likely results from
reduced carbon allocation to unaccounted components of net primary production, particularly root symbionts.
