Comparison of Carbon Dynamics among Three Cool-Temperate Forests (Quercus serrata, Larix kaempferi and Pinus densiflora) under the Same Climate Conditions in Japan

To understand the role of forest ecosystems in the global carbon cycle, it is important to clarify the factors affecting the carbon balance of forest ecosystems. However, little is known about the direct effect of forest types, especially dominant species, on their different carbon dynamics. To clarify the effect of difference in forest types, an experiment was conducted in three forests, which were located in the same place and exposed to the same climate conditions. These forests were middle-aged (40 - 45 years) and dominated by Quercus serrata (Q forest), Larix kaempferi (L forest) and Pinus densiflora (P forest). Net primary production (NPP), heterotrophic respiration (HR) and net ecosystem production (NEP) were estimated in each forest, using a biometric method over one year. For NPP estimated from the annual growth of tree biomass (ΔB) and amount of litter (LF), P forest NPP (5.3 MgC·ha-1·yr-1) was higher than Q and L forest NPP (4.6 and 3.2 MgC·ha-1·yr-1). The difference was affected by a significant difference in ΔB (p = 0.032) and LF (p -1·yr-1) was higher than L and P forest (2.3 and 2.1 MgC·ha-1·yr-1). This difference could result from the amount of litter (respiration substrate) and chemical properties of litter (lability of decomposition). The NEP, which was calculated from the difference between NPP and HR, varied widely among the forest types (0.5, 0.9 and 3.2 MgC·ha-1·yr-1 in Q, L and P forests, respectively). The range of values among the forest types was comparable to those among age sequences and climate zones in previous studies. These results suggest that the difference in forest types (especially dominant species) can potentially lead to a large variation in carbon dynamics, in ecosystems located in the same place.