Site‐Related ^(13)C of Tree Leaves and Soil Organic Matter in a Temperate Forest

Abstract

In order to relate the isotopic composition of soil organic matter to parent vegetation and soil type, we measured the carbon stable isotope ratios of tree leaves and soil Cat 14 locations in a temperate forest. Sites were selected over a wide variety of soil types and related vegetation associations, but within a single regional climate. The o 13 C of the bulk leaf material falling on the soil varied among sites, ranging from -29.5 to -26o/oo. Within this range, differences up to 1.5o/oo were attributable to differences in tree species.Further differences were related to site. The o 13 C values of soil organic matter cover the range -29.8 to -24.3o/oo and varied with both parent vegetation o 13 C and depth. Transformation and decay of organic C within the litter layers led to no isotope enrichment, irrespective of vegetation and humus type: mull, hydro mull, moder, or anmoor. The difference between woody and leaf material in litter was low, 0.23 ± 0.35 o/oo (mean ± 1 SD).On the other hand o 13 C in mineral horizons always increased with depth, reaching values richer than litter by 1.0 ± 0.5o/oo at 20 em and up to + 1.5o/oo at 1 m. The trend was independent of the soil physico-chemical characteristics, whether aerobic, anaerobic, eutrophic, oligotrophic, or podzolic. Isotope ratios of soil organic C in forests appear to provide useful estimators of tree isotopic composition. When compared to the measurements ofthe vegetation, they offer the advantage of an easily obtained value that naturally integrates over plant material, time and, eventually, local area.

Evaluation of structural chemistry and isotopic signatures of refractory soil organic carbon fraction isolated by wet oxidation methods

“…The largest enrichment of 13 C was therefore associated with the SOC present in the H 2 O 2 resistant residue after LF removal. These results are in accord with other studies that documented enrichment of heavier 13 C compared to lighter 12 C with increasing degree of SOM decomposition (Nadelhoffer and Fry 1988;Balesdent et al 1993;Bernoux et al 1998). Such a trend in d 13 C signatures was not observed in soils from cultivated sites, where the d 13 C signatures of contemporary plant inputs are a mixture of both C 3 native species (average d 13 C of -27%) and C 4 corn (average d 13 C of -12%) ( Table 5).…”

Dissolved organic carbon and its carbon isotope compositions in hill slope soils of the karst area of southwest China: Implications for carbon dynamics in limestone soil

“…For instance, Del Galdo et al (2003) found that the δ 13 C values of organic carbon in the soil profiles of forests or grass generally increased with increasing soil depth, and attributed this mainly to the isotope fractionation during litter decomposition and humification instead of the physical and chemical properties of soil. These results have also been ascribed to the tendency of microbes to utilize compounds containing 12 C rather than 13 C (Balesdent et al, 1993). The surface SOM is basically composed of newly supplemented unstable organic carbon.…”

The use of δ13C values of leporid teeth as indicators of past vegetation

“…The analytical precision for these data is ±0.24‰ based upon repeated measurements of an in-house standard, which was used to correct raw measured values to the VPDB scale. The bulk sediment organic carbon δ 13 C record is interpreted as reflecting the δ 13 C value of the surrounding vegetation at the time of deposition with little to no isotopic enrichment during diagenesis (Balesdent et al, 1993), and provides a record of changes in the relative abundance of C 3 /C 4 plants to which we can compare our tooth isotope data.…”