CARBON ISOTOPIC RATIOS (13C/12C) IN PEAT-FORMING PLANTS: CALIBRATION FOR PALAEOCLIMATIC RECONSTRUCTIONS (AIR TEMPERATURE AND HUMIDITY)

The recent peat (the uppermost 0-15 cm layer) and alive green plants (Sphagnum Sp. and Polytrichum Sp.) have been collected from the N slope of Karkonosze Mts. (SW Poland) at following altitudes: 739, 834, 915, 1052, 1092, 1240, 1266, 1393m a.s.l. Automatic measurements of temperature and humidity with 1-hour interval during vegetation season have been carried out at each sampling point.

Good correlations between C-isotope ratios in the Sphagnum Sp. - Polytrichum Sp., Sphagnum Sp. - peat and Polytrichum Sp. - peat systems (R²= 0.93, 0.95 and 0.91, respectively) suggest that probably the same major factor(s) control(s) C isotope signatures in peat. Correlations (R²) between the day-light temperature of vegetation period (T_dl) and d¹³C value of Sphagnum, Polytrichum and peat were 0.68, 0.72 and 0.76, respectively. This confirms the thesis that temperature is the most important factor controlling carbon isotopic composition of peat-forming plant tissue. It has been preliminary calculated that the variation of Fq average value for recent peat is up to -1.68‰/ºC, i.e. 1˚C increase in daytime temperature (during vegetation period) corresponds to -1.68‰ change in d¹³C value in uppermost layer of peat (0-15cm). In contrast to temperature, the humidity shows no influence to carbon isotope composition of peat-forming plants.

Concordant variations of the d¹³C_{nitrocellulose} and d¹³C_total values in peat evidence is reliable (with negligible role of diagenetic processes) calibration of the Fq value (Jedrysek and Skrzypek 2005a), hence its relevance to palaeoclimatic reconstructions (Skrzypek and Jedrysek 2005b). It is in agreement to our previous results showing: 1) high horizontal homogeneity of d¹³C_total value for peat bogs, 2) concordant variations of d¹³C, in tree-ring cellulose and total organic matter from peat core profiles, compared to temperature variations in lowlands of England (Jedrysek et al. 2003).

 

References

Jedrysek M.O., Krapiec M., Skrzypek G., and Kaluzny A., 2003, Water, Air and Soil Pollution 145, 359-375.

Jedrysek M.O., Skrzypek G., 2005a, Environmental Chemistry Letters 2(4): 179-183.

Skrzypek G. and Jedrysek M.O., 2005b, In: Environmental Chemistry - Green Chemistry and Pollutants in Ecosystems. Springer-Verlag: 65-73.