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Interactions Among Abiotic Drivers, Disturbance and Gross Ecosystem Carbon Exchange on Soil Respiration from Subtropical Pine Savannas

Wiesner, Susanne, Staudhammer, Christina L., Loescher, Henry W., Baron-Lopez, Andres, Boring, Lindsay R., Mitchell, Robert J., Starr, Gregory
Ecosystems 2018 v.21 no.8 pp. 1639-1658
Pinus palustris, air temperature, biotic factors, carbon, carbon dioxide, climate, drought, eddy covariance, mineralization, models, prescribed burning, rain, regrowth, savannas, soil respiration, soil water, soil water content
Globally, soil CO₂ efflux rates (Fₛ) have been linked to changes in soil water content (SWC), rainfall and temperature and/or productivity. However, within an ecosystem, Fₛ can vary based on site structure and function, which can be affected by a combination of abiotic and biotic factors. This becomes particularly important when an ecosystem is faced with disturbances, such as drought or fire. Site-specific compensatory responses to disturbances may therefore alter C mineralization, as well as root respiration. Hence, single location Fₛ estimates may not be a representative for ecosystems across their distributional ranges. We conducted a 6-year study along an edaphic moisture gradient of longleaf pine ecosystems that were maintained with prescribed fire, using eddy covariance and soil respiration measurements to address how Fₛ varies with changes in ecosystem structure and function, as well as disturbances. Lower air temperatures (Tₐᵢᵣ) decreased Fₛ at all sites, but that response was also affected by productivity and SWC. Productivity significantly altered Fₛ rates at all sites, especially when we accounted for changes in temperature and SWC. Plant regrowth post-fire temporarily increased Fₛ (10–40%), whereas drought reduced Fₛ at all sites. Our results show that site productivity, Fₛ and the degree to which ecosystems adapt to climate variations and disturbance can be site specific. Hence, model forecasting of carbon dynamics would strongly benefit from multi-location measurements of Fₛ across the distributional range of an ecosystem.