Landscape structure, groundwater dynamics, and soil water content influence soil respiration across riparian-hillslope transitions in the Tenderfoot Creek Experimental Forest, Montana
2011
Pacific, Vincent J. | McGlynn, Brian L. | Riveros-Iregui, Diego A. | Welsch, Daniel L. | Epstein, Howard E.
Variability in soil respiration at various spatial and temporal scales has been the focus of much research over the last decade aimed to improve our understanding and parameterization of physical and environmental controls on this flux. However, few studies have assessed the control of landscape position and groundwater table dynamics on the spatiotemporal variability of soil respiration. We investigated growing season soil respiration in a ∼393 ha subalpine watershed in Montana across eight riparian-hillslope transitions that differed in slope, upslope accumulated area (UAA), aspect, and groundwater table dynamics. We collected daily-to-weekly measurements of soil water content (SWC), soil temperature, soil CO₂ concentrations, surface CO₂ efflux, and groundwater table depth, as well as soil C and N concentrations at 32 locations from June to August 2005. Instantaneous soil surface CO₂ efflux was not significantly different within or among riparian and hillslope zones at monthly timescales. However, cumulative integration of CO₂ efflux during the 83-day growing season showed that efflux in the wetter riparian zones was ∼25% greater than in the adjacent drier hillslopes. Furthermore, greater cumulative growing season efflux occurred in areas with high UAA and gentle slopes, where groundwater tables were higher and more persistent. Our findings reveal the influence of landscape position and groundwater table dynamics on riparian versus hillslope soil CO₂ efflux and the importance of time integration for assessment of soil CO₂ dynamics, which is critical for landscape-scale simulation and modelling of soil CO₂ efflux in complex landscapes.
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