Carbon dioxide efflux from long-term grazing management systems in a semiarid region
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Grazing management can affect grassland carbon (C) dynamics, yet limited information is available documenting management effects on carbon dioxide (CO2) efflux. A study was conducted to quantify the role of long-term grazing management to affect CO2 efflux within the semiarid northern Great Plains of North America. Grazing management systems evaluated in the study included two native vegetation pastures differing in stocking rate [moderately grazed pasture (MGP), heavily grazed pasture (HGP)] and a fertilized, grazed crested wheatgrass [Agropyron desertorum (Fisch. ex. Link) Schult.] pasture (CWP) near Mandan, ND, USA. Carbon dioxide efflux was measured on 1-2 week intervals for three years using static chamber methodology. Supplemental assessments of soil temperature and water content, aboveground live biomass, root biomass, and soil microbial biomass C were conducted during each growing season. Carbon dioxide efflux did not differ between native vegetation pastures differing in stocking rate. However, mean hourly CO2 efflux was greater in CWP (100.1mgCm-2h-1) than HGP (81.1mgCm-2h-1) (P=0.03), a result attributed to prevalence of cool-season grass and high available N in CWP. Carbon dioxide efflux differed among grazing treatments during spring (March-May) and fall (September-November), but not winter (December-February) and summer (June-August). Associations between CO2 efflux and abiotic factors were seasonally dependent, with positive associations between efflux and soil temperature during spring (r=0.71, P0.01) and fall (r=0.45, P0.01) and efflux and water-filled pore space (WFPS) during summer (r=0.46, P0.01). In this study, increased stocking rate did not contribute to elevated CO2 efflux within native vegetation pastures. Given strong weather-dependence on grassland productivity, long-term monitoring is necessary to confidently discern grazing management effects on C dynamics. 2012.
Agriculture Ecosystems & Environment
author list (cited authors)
Liebig, M. A., Kronberg, S. L., Hendrickson, J. R., Dong, X., & Gross, J. R.
complete list of authors
Liebig, MA||Kronberg, SL||Hendrickson, JR||Dong, X||Gross, JR