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Climate-related research activities at the Loch Vale WEBB site

Climatic controls on solute fluxes and CO2 consumption via weathering

Solute fluxes in streams, which are the product of concentration times discharge, are strongly affected by variations in climate. Research in Loch Vale, and subsequently confirmed at many other headwater catchments in the United States, has documented that concentrations of weathering products exhibit relatively little variability in relation to changes in precipitation, discharge, or annual runoff [Clow, 1992; Clow and Drever, 1996; Godsey et al., submitted 2008]. As a result, fluxes of weathering products increase almost in direct proportion to annual variations in precipitation. This has important implications for carbon budgets because weathering of silicate minerals in pristine catchments is driven primarily by carbonic-acid dissolution reactions, which consume CO2. Exploring the mechanisms for this "chemostatic" behavior is an area of active research for the WEBB program [Clow and Drever, 1996; Godsey et al., submitted 2008; White and Blum, 1995a; White and Blum, 1995b; White et al., 1999]. A hydrograph separation study by Mast [1995] using water isotopes and silica documented that fast reactions in the soil must play an important role. Dilution of weathering products during wet periods with concomitant increases in weathering rates also may be important [Drever and Clow, 1995].

In contrast to fluxes of weathering products, nitrogen fluxes in Loch Vale are not strongly related to annual precipitation amount [Campbell et al., 2000]. Currently, nitrogen assimilation in alpine terrain is limited by cold temperatures; however, increasing trends in air temperatures and lengthening growing seasons may increase nitrogen assimilation rates.

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