Koong Yi

Simulating the soil carbon dynamics of Pinus densiflora forests in central Korea

Abstract We developed a simple forest soil carbon model (Korean Forest Soil Carbon model, KFSC) requiring a small number of parameters to evaluate the forest soil carbon stocks and dynamics. The KFSC was composed of live biomass (BIO), primary dead organic matter (DOM) (AWD: aboveground woody debris; BWD: belowground woody debris; ALT: aboveground litter; and BLT: belowground litter), and secondary DOM (HUM: humus and SOC: soil organic carbon). The KFSC was validated against six Pinus densiflora forests at Gyeonggi province in central Korea and validation results showed that the model predicted the AWD, ALT, and SOC stocks with high precision (r 2=0.90–0.98, slope = 0.95–0.98). We simulated 160 years of carbon dynamics of the P. densiflora forests in Gyeonggi province (11,607 ha) under alternative clear-cut intervals that had been taking place in the past (30, 50, and 80 years). Simulated total SOC stock ranged from 298.7 to 520.5 Gg C depending on the scenario and increased with time in all scenarios. The estimated total SOC stock was higher in the scenario of less frequent clear-cut, while its annual increment was higher in the scenario of more frequent clear-cut in the past. The KFSC will be useful, especially for simulating soil carbon dynamics in forests with scarce information, and has the potential to estimate soil carbon dynamics at a national scale by incorporating with geographical information system.

Preliminary study on estimating fine root growth in a natural Pinus densiflora forest using a minirhizotron technique

The minirhizotron technique was used to investigate the spatial (soil depth) and temporal (season) changes of fine roots (≤2 mm) in a mature Pinus densiflora forest. Length, production, and mortality of fine roots were measured at different depths on seven dates between March and October 2011. Average fine root length (mm cm−2), production, and mortality (μm cm−2) during the growing seasons were 2.54 ± 0.82, 84 ± 27, and 7 ± 4 at 0–20 cm depth, 0.85 ± 0.37, 39 ± 13, and 14 ± 9 at 20–40 cm depth, and 1.26 ± 0.92, 45 ± 28, and 34 ± 16 at 40–60 cm depth, respectively. There was no significant difference in length, production, or mortality of fine roots among the different seasons and depths (P > 0.05). The seasonal pattern in fine root length generally increased during the growing seasons. The fine root production was high in summer, whereas the mortality was high in autumn. This preliminary result using a minirhizotron technique can be used for quantifying and understanding the fine root dynamics in P. densiflora forests.

Differences in soil aggregate, microbial biomass carbon concentration, and soil carbon between Pinus rigida and Larix kaempferi plantations in Yangpyeong, central Korea

This study was conducted to examine the soil aggregate distributions and their relationship with microbial biomass carbon (C) concentration and soil C in Pinus rigida and Larix kaempferi plantations. Soil samples of 0–10 cm, 10–20 cm, and 20–30 cm depth were collected and the microbial biomass C concentration was measured. The soils were then classified into four aggregate size classes by wet-sieving procedure [large macroaggregate (>2000 μm), small macroaggregate (250–2000 μm), microaggregate (53–250 μm), and silt-plus-clay (<53 μm)] and the C content of each aggregate size class was analyzed. The L. kaempferi plantation contained more macroaggregate over 250 μm than the P. rigida plantation did. The mean weight diameter (MWD) of the soil aggregate up to 30 cm depth was 1.26 mm and 1.45 mm in the P. rigida and L. kaempferi plantations, respectively, and it decreased with soil depth. The microbial biomass C concentration up to 30 cm depth was 510 μg C g soil−1 for the P. rigida plantation and 764μg C g soil−1 for the L. kaempferi plantation, and it was greatest in the surface soil in both plantations. The mean soil C concentration up to 30 cm depth was 2.00% for the P. rigida plantation and 2.88% for the L. kaempferi plantation. In both plantations, the soil C concentration was higher in the surface soil than in the deep soil. However, there was no significant difference of C concentration among the soil aggregate size classes. The soil C content up to 30 cm depth in the P. rigida and L. kaempferi plantations were 47.69 Mg ha−1 and 61.49 Mg ha−1, respectively, and were also higher in the surface soil than in the deep soil. In both plantations, macroaggregate contained more Ccontent than microaggregate did. The microbial biomass C and soil C concentrations were significantly higher (P < 0.05) in the L. kaempferi plantation than in the P. rigida plantation due to the effect of species difference. The MWD and C content tended to be greater in the L. kaempferi plantation than in the P. rigida plantation, but the differences were not significant. In this study, the soil aggregate size, microbial biomass C and soil C concentrations were positively correlated with one another.

Mass dynamics of coarse woody debris in an old-growth deciduous forest of Gwangneung, Korea

We investigated the mass dynamics of coarse woody debris (CWD) in an old-growth deciduous forest dominated by Quercus serrata, Carpinus laxiflora, and C. cordata in a 1 ha permanent plot of the Gwangneung Experiment Forest, Korea, from 2002 through 2010. CWD mass varied from 16.8 to 34.2 Mg ha−1, and the ratio of CWD mass to stand biomass varied from 0.06 to 0.13. The mean CWD mass input and loss rates were 4.81 Mg ha−1 yr−1 and 2.28 Mg ha−1 yr−1, respectively. A large heterogeneity of CWD mass, as represented by the spatial coefficient of variation (127.2%) and annual coefficient of variation (178.5%), might be inherent in the old-growth temperate forest, which consisted of large biomass trees. The decay rate constant, as estimated from the wood density change, was 0.049yr−1. However, the large variation of annual CWD mass input could cause the overestimation of decay rate constant (0.167 yr−1) as calculated from the ratio of CWD mass input to CWD mass. According to the CWD decay class classification, class II (72.8%) comprised the majority of CWD mass. The proportion of CWD mass to total CWD mass was 57.5% for Q. serrata, 25.0% for C. laxiflora, and 10.4% for C. cordata, respectively, and corresponded to the proportion of stem biomass to total stem biomass. These data support the stability of the current status in this old-growth deciduous forest as representing the climax stage. Due to the relatively short-term measurement of CWD mass compared with the whole life span of CWD, additional long-term studies with various approaches are required to enhance the knowledge of CWD mass dynamics in this forest.