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Diurnal variations and vertical distribution of δ13C, and concentration of atmospheric and soil CO2 in a meadow site, SE Poland

Szaran J., Dudziak A., Trembaczowski A., Niezgoda H., Hałas S.

Geological Quarterly

2005

Vol. 49, No. 2

135--144

We provide the results of 24-hour observations made in a meadow site located in a small river valley in Central Europe. Samples of atmospheric air were taken from three horizons: near the soil (0.05 m), in the grass (0.5 m) and above the meadow (2 m) at two-hour intervals. At the same time, samples of soil air were collected from two horizons: -0.1 and -0.5 m. We have found a variation of δ¹³C above the ground from -6‰ during the day to -20‰ late at night accompanied by variations in CO₂ concentration from 270 ppm during the day, to various levels late at night at different heights above the ground. The maximum concentration was 1430 ppm at the ground level. The correlation coefficient between δ¹³C and reciprocal of concentration was the highest (R2 = 0.984) for the samples collected 2 m above the ground, the regression line clearly indicating CO₂ mixing from the two sources: atmospheric and biogenic reservoirs. The intercept of the mixing line yields δC = -23.0‰ for the biogenic CO₂. In contrast, the diurnal variations in the soil were relatively small, δ¹³C varied from -21.6 to -23.4‰, while CO₂ concentration from 4300 to 8200 and from 24 700 to 34 500 ppm at depths of 0.1 m and 0.5 m respectively, which is less than 2-fold. Small diurnal variations are characteristic of dry soils, where δ^13C is weakly correlated with CO₂ concentration (in our case R2 was 0.30 and 0.54, respectively).

Delta 13C in tree rings alfa-cellulose. A methodology of measurements and interpretation: state of the art

Pawełczyk S., Pazdur A.

Geochronometria

2000

Vol. 18

15-18

The development of a tree is dependent upon the climatic and environmental conditions under which it grows. Formed growth rings represent integration of these variables during each growing season. More parameters other than ring-width are required to produce satisfactory reconstruction of past environmental changes. Stable isotope variations within the growth rings may provide other parameters. The variation of delta13C indices in the latewood alpha-cellulose is highly correlated with combined July and August environmental variables. Investigation of isotopic carbon composition in annual tree rings from Upper Silesia and ecologically clean Augustów Wilderness region were recently undertaken in the 14C Laboratory in Gliwice. In that time a series of radiocarbon concentration measurements in single tree rings and delta13C in the entire organic matter were carried out. Such evaluated values of delta 13C are used to correct radiocarbon concentration. However they cannot be used to reconstruct climatic and environmental conditions.