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Elevated CO2 stimulates grassland soil respiration by increasing carbon inputs rather than by enhancing soil
 

Summary: Elevated CO2 stimulates grassland soil respiration by
increasing carbon inputs rather than by enhancing soil
moisture
E . C A R O L A D A I R * § , P E T E R B . R E I C H , J A R E D J . T R O S T and SARAH E. HOBBIE§
*National Center for Ecological Analysis and Synthesis, University of California Santa Barbara, Santa Barbara, CA, 93101, USA,
Department of Forest Resources, University of Minnesota, Saint Paul, MN, 55108, USA, Cedar Creek Ecosystem Science
Reserve, East Bethel, MN, 55005, USA, §Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul,
MN, 55108, USA
Abstract
It is not clear whether the consistent positive effect of elevated CO2 on soil respiration (soil carbon flux, SCF) results
from increased plant and microbial activity due to (i) greater C availability through CO2-induced increases in C
inputs or (ii) enhanced soil moisture via CO2-induced declines in stomatal conductance and plant water use. Global
changes such as biodiversity loss or nitrogen (N) deposition may also affect these drivers, interacting with CO2 to
affect SCF. To determine the effects of these factors on SCF and elucidate the mechanism(s) behind the effect of
elevated CO2 on SCF, we measured SCF and soil moisture throughout a growing season in the Biodiversity, CO2, and
N (BioCON) experiment. Increasing diversity and N caused small declines in soil moisture. Diversity had inconsis-
tent small effects on SCF through its effects on abiotic conditions, while N had a small positive effect that was
unrelated to soil moisture. Elevated CO2 had large consistent effects, increasing soil moisture by 26% and SCF by
45%. However, CO2-induced changes in soil moisture were weak drivers of SCF: CO2 effects on SCF and soil mois-
ture were uncorrelated, CO2 effect size did not change with soil moisture, within-day CO2 effects via soil moisture

  

Source: Adair, E. Carol - National Center for Ecological Analysis and Synthesis, University of California at Santa Barbara
Minnesota, University of - Cedar Creek Natural History Area

 

Collections: Environmental Sciences and Ecology