Increases in the flux of carbon belowground stimulate nitrogen uptake and sustain the long-term enhancement of forest productivity under elevated CO₂
Drake, John E. | Gallet-Budynek, Anne | Hofmockel, Kirsten S. | Bernhardt, Emily S. | Billings, Sharon A. | Jackson, Robert B. | Johnsen, Kurt S. | Lichter, John | McCarthy, Heather R. | McCormack, M Luke | Moore, David J.P. | Oren, Ram | Palmroth, Sari | Phillips, Richard P. | Pippen, Jeffrey S. | Pritchard, Seth G. | Treseder, Kathleen K. | Schlesinger, William H. | DeLucia, Evan H. | Finzi, Adrien C.
Ecology Letters (2011) 14: 349-357 ABSTRACT: 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.
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