Increases in the flux of carbon belowground stimulate nitrogen uptake and sustain the long-term enhancement of forest productivity under elevated CO₂.
The earth's future climate state is highly dependent upon changes in terrestrial C storage in response to rising concentrations of atmospheric CO₂. Here we show that consistently enhanced rates of net primary production (NPP) are sustained by a C-cascade through the root-microbe-soil system; increases in the flux of C belowground under elevated CO₂ stimulated microbial activity, accelerated the rate of soil organic matter decomposition and stimulated tree uptake of N bound to this SOM. This process set into motion a positive feedback maintaining greater C gain under elevated CO₂ as a result of increases in canopy N content and higher photosynthetic N-use efficiency. The ecosystem-level consequence of the enhanced requirement for N and the exchange of plant C for N belowground is the dominance of C storage in tree biomass but the preclusion of a large C sink in the soil.
Drake, JE; Gallet-Budynek, A; Hofmockel, KS; Bernhardt, ES; Billings, SA; Jackson, RB; Johnsen, KS; Lichter, J; McCarthy, HR; McCormack, ML; Moore, DJP; Oren, R; Palmroth, S; Phillips, RP; Pippen, JS; Pritchard, SG; Treseder, KK; Schlesinger, WH; Delucia, EH; Finzi, AC
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