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Carbon limitation of soil respiration under winter snowpacks: potential feedbacks between growing season and winter carbon fluxes
Author(s) -
Brooks Paul D.,
McKnight Diane,
Elder Kelly
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.1365-2486.2004.00877.x
Subject(s) - environmental science , soil respiration , snow , soil carbon , growing season , carbon cycle , litter , carbon fibers , ecosystem , soil water , plant litter , nutrient , atmospheric sciences , agronomy , ecology , soil science , biology , geology , composite number , composite material , geomorphology , materials science
A reduction in the length of the snow‐covered season in response to a warming of high‐latitude and high‐elevation ecosystems may increase soil carbon availability both through increased litter fall following longer growing seasons and by allowing early winter soil frosts that lyse plant and microbial cells. To evaluate how an increase in labile carbon during winter may affect ecosystem carbon balance we investigated the relationship between carbon availability and winter CO 2 fluxes at several locations in the Colorado Rockies. Landscape‐scale surveys of winter CO 2 fluxes from sites with different soil carbon content indicated that winter CO 2 fluxes were positively related to carbon availability and experimental additions of glucose to soil confirmed that CO 2 fluxes from snow‐covered soil at temperatures between 0 and −3°C were carbon limited. Glucose added to snow‐covered soil increased CO 2 fluxes by 52–160% relative to control sites within 24 h and remained 62–70% higher after 30 days. Concurrently a shift in the δ 13 C values of emitted CO 2 toward the glucose value indicated preferential utilization of the added carbon confirming the presence of active heterotrophic respiration in soils at temperatures below 0°C. The sensitivity of these winter fluxes to substrate availability, coupled with predicted changes in winter snow cover, suggests that feedbacks between growing season carbon uptake and winter heterotrophic activity may have unforeseen consequences for carbon and nutrient cycling in northern forests. For example, published winter CO 2 fluxes indicate that on average 50% of growing season carbon uptake currently is respired during the winter; changes in winter CO 2 flux in response to climate change have the potential to reduce substantially the net carbon sink in these ecosystems.