Abstract: The litters, bulk soils, and soil particle-size fractions were sampled from three typical natural forests, i.e., broadleaf Korean pine (Pinus koraiensis)mixed forest   (PB, altitude 740 m), spruce-fir (Picea asperata- Abies nephrolepis) forest (SF, altitude 1350 m), and  Erman’s birch (Betula ermanii) forest (EB, altitude 1996 m), on the northern slope of Changbai Mountains to analyze their organic matter δ¹³C values, and the intact soil cores (20 cm depth) from EB (high altitude) were relocated to PB and SF (low altitudes) for a year to study the responses of the δ¹³C values to simulated warming. It was shown that the litters had a significantly lower δ¹³C value than the soils, and the δ¹³C values of the litters and soils increased downward through the litter- and soil layers in all the three typical forest types. Soil particlesize fractions had an increased δ¹³C value with decreasing particle size fractions. The δ¹³C value of the litters was in the order of SF (-28.3‰)>PB (-29.0‰) >EB (-29.6‰), while that of the soils was in the order of EB (-25.5‰) >PB (-25.8‰) >SF (-26.2‰). Over one-year soil warming (an increment of 0.7 ℃-2.9 ℃), the δ¹³C values of  the bulk soils and soil particle-size fractions all presented a decreasing  trend, and the decrement of the δ¹³C value was larger in <2 μm (0.48‰) and 2-63 μm fractions (0.47‰) than in >63 μm fraction (0.33‰).  The results suggested that climate warming could have great effects on the older organic carbon associated with fine soil particle-size fractions.

Key words: Changbai Mountains, altitudinal transect, stable carbon isotope, simulated warming, soil core relocation experiment, soil particle-size fraction