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Increased belowground biomass and soil CO2 fluxes after a decade of carbon dioxide enrichment in a warm-temperate forest

Jackson, RB, CW Cook, JS Pippen, SM Palmer
Journal Volume/Pages: 
90: 3352-3366

Atmospheric CO2 concentrations have risen 40% since the start of the industrial revolution. Beginning in 1996, the Duke Free-Air CO2 Enrichment experiment has exposed plots in a loblolly pine forest to an additional 200 µl l-1 CO2 compared to trees growing in ambient CO2. This paper presents new belowground data and a synthesis of results through 2008, including root biomass and nutrient concentrations, soil respiration rates, soil pore-space CO2 concentrations, and soil-solution chemistry to 2-m depth. On average in elevated CO2, fine root biomass in the top 15 cm of soil increased by 24%, or 59 g m-2 (26 g m-2 C; P0.30), suggesting greater belowground plant demand for N in high CO2. Soil respiration was significantly higher by 23% on average (P10,000 µl l-1 higher at 70- and 100-cm depths, potentially influencing soil acidity and rates of weathering. Soil solution Ca2+ and total base cation concentrations were 140% and 176% greater, respectively, in elevated CO2 at 200 cm depth (P

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