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Abstract:
Studies of the seasonality, spatial variation and geomorphic effects of Soil CO2 concentrations in a summer-dry subalpine karst landscape in the Marble Mountains, Klamath National Forest, California, demonstrate the significance of soil moisture as a limiting factor. Modeled actual evapotranspiration (AET) in the four weeks prior to sampling explains 36% of the observed soil-CO2 concentrations, pointing to the importance of root respiration processes in these systems. Late snows are significant in controlling the timing of a snowmelt-initiated pulse of respiration and groundwater. CO2 concentrations were measured at multiple sites in two seasons - 1995 and 1997 - with contrasting patterns of snowmelt. Other than wet-meadow anomalies, where CO2 concentrations reached up to 3.8% in midsummer, alpine meadows on schist were the sites of the highest spring peak concentrations of approximately 1%. Forest sites and sites with thin soils on marble typically peaked at approximately 0.5%, also within a month of snowmelt exposure. Ongoing karstification in the upper bare karst is focused in soil-filled grikes where late-season snowmelt concentrates flow during high-respiration periods, but the lack of active speleothem development suggests that the carbonate solution system is greatly reduced from preglacial periods