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Growth of Eastern Cottonwoods ( Populus deltoides ) in elevated [CO 2 ] stimulates stand‐level respiration and rhizodeposition of carbohydrates, accelerates soil nutrient depletion, yet stimulates above‐ and belowground biomass production
Author(s) -
BarronGafford Greg,
Martens Dean,
Grieve Katie,
Biel Karl,
Kudeyarov Valery,
McLain Jean E. T.,
Lipson David,
Murthy Ramesh
Publication year - 2005
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2005.00985.x
Subject(s) - soil respiration , biomass (ecology) , environmental science , nutrient , growing season , primary production , soil carbon , agronomy , canopy , coppicing , ecosystem , mesocosm , deciduous , soil water , botany , woody plant , biology , ecology , soil science
We took advantage of the distinctive system‐level measurement capabilities of the Biosphere 2 Laboratory (B2L) to examine the effects of prolonged exposure to elevated [CO 2 ] on carbon flux dynamics, above‐ and belowground biomass changes, and soil carbon and nutrient capital in plantation forest stands over 4 years. Annually coppiced stands of eastern cottonwoods ( Populus deltoides ) were grown under ambient (400 ppm) and two levels of elevated (800 and 1200 ppm) atmospheric [CO 2 ] in carbon and N‐replete soils of the Intensive Forestry Mesocosm in the B2L. The large semiclosed space of B2L uniquely enabled precise CO 2 exchange measurements at the near ecosystem scale. Highly controllable climatic conditions within B2L also allowed for reproducible examination of CO 2 exchange under different scales in space and time. Elevated [CO 2 ] significantly stimulated whole‐system maximum net CO 2 influx by an average of 21% and 83% in years 3 and 4 of the experiment. Over the 4‐year experiment, cumulative belowground, foliar, and total aboveground biomass increased in both elevated [CO 2 ] treatments. After 2 years of growth at elevated [CO 2 ], early season stand respiration was decoupled from CO 2 influx aboveground, presumably because of accelerated fine root production from stored carbohydrates in the coppiced system prior to canopy development and to the increased soil carbohydrate status under elevated [CO 2 ] treatments. Soil respiration was stimulated by elevated [CO 2 ] whether measured at the system level in the undisturbed soil block, by soil collars in situ , or by substrate‐induced respiration in vitro . Elevated [CO 2 ] accelerated depletion of soil nutrients, phosphorus, calcium and potassium, after 3 years of growth, litter removal, and coppicing, especially in the upper soil profile, although total N showed no change. Enhancement of above‐ and belowground biomass production by elevated [CO 2 ] accelerated carbon cycling through the coppiced system and did not sequester additional carbon in the soil.