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Impacts of an anomalously warm year on soil CO 2 efflux in experimentally manipulated tallgrass prairie ecosystems
Author(s) -
Verburg Paul S. J.,
Larsen Jessica,
Johnson Dale W.,
Schorran David E.,
Ar John A.
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.1365-2486.2005.001032.x
Subject(s) - soil respiration , environmental science , ecosystem , ecosystem respiration , primary production , lysimeter , atmospheric sciences , chemistry , hydrology (agriculture) , soil water , soil science , environmental chemistry , ecology , biology , geology , geotechnical engineering
Modeling analyses suggest that an increase in growth rate of atmospheric CO 2 concentrations during an anomalously warm year may be caused by a decrease in net ecosystem production (NEP) in response to increased heterotrophic respiration ( R h ). To test this hypothesis, 12 intact soil monoliths were excavated from a tallgrass prairie site near Purcell, Oklahoma, USA and divided among four large dynamic flux chambers (Ecologically Controlled Enclosed Lysimeter Laboratories (EcoCELLs)). During the first year, all four EcoCELLs were subjected to Oklahoma air temperatures. During the second year, air temperature in two EcoCELLs was increased by 4°C throughout the year to simulate anomalously warm conditions. This paper reports on the effect of warming on soil CO 2 efflux, representing the sum of autotrophic respiration ( R a ) and R h . During the pretreatment year, weekly average soil CO 2 efflux was similar in all EcoCELLs. During the late spring, summer and early fall of the treatment year, however, soil CO 2 efflux was significantly lower in the warmed EcoCELLs. In general, soil CO 2 efflux was correlated with soil temperature and to a lesser extent with moisture. A combined temperature and moisture regression explained 64% of the observed variation in soil CO 2 efflux. Soil CO 2 efflux correlated well with a net primary production (NPP) weighted greenness index derived from digital photographs. Although separate relationships for control and warmed EcoCELLs showed better correlations, one single relationship explained close to 70% of the variation in soil CO 2 efflux across treatments and years. A strong correlation between soil CO 2 efflux and canopy development and the lack of initial response to warming indicate that soil CO 2 efflux is dominated by R a . This study showed that a decrease in soil CO 2 efflux in response to a warm year was most likely dominated by a decrease in R a instead of an increase in R h .