, Volume 43, Issue 1, pp 43-61

Carbon pools and fluxes along an environmental gradient in northern Arizona

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Carbon pools and fluxes were quantified along an environmentalgradient in northern Arizona. Data are presented on vegetation, litter, andsoil C pools and soil CO2 fluxesfrom ecosystems ranging from shrub-steppe through woodlands to coniferousforest and the ecotones in between. Carbon pool sizes and fluxes in thesesemiarid ecosystems vary with temperature and precipitation and are stronglyinfluenced by canopy cover. Ecosystem respiration is approximately 50percent greater in the more mesic, forest environment than in the dryshrub-steppe environment. Soil respiration rates within a site varyseasonally with temperature but appear to be constrained by low soilmoisture during dry summer months, when approximately 75% of totalannual soil respiration occurs. Total annual amount of CO2 respired across all sites ispositively correlated with annual precipitation and negatively correlatedwith temperature. Results suggest that changes in the amount and periodicityof precipitation will have a greater effect on C pools and fluxes than willchanges in temperature in the semiarid Southwestern United States.