Increases in the flux of carbon belowground stimulate nitrogen uptake and sustain the long-term enhancement of forest productivity under elevated CO2

Authors: Drake, JE, A Gallet-Budynek, KS Hofmockel, ES Bernhardt, SA Billings, RB Jackson, KS Johnsen, J Lichter, HR McCarthy, ML McCormack, DJP Moore, R Oren, S Palmroth, RP Phillips, JS Pippen, SG Pritchard, KK Treseder, WH Schlesinger, EH DeLucia, AC Finzi

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.


el2011.pdf