Quantitative evaluation for carbon storage of trees planted in an urban area is important for carbon sequestration management. This study was conducted to develop allometric equations to estimate the carbon storage of three representative urban tree species [Ginkgo biloba Linn., Zelkova serrata (Thunb.) Makino., and Prunus × yedoense Matsum.] planted in Jinju, Gyeongsangnam-do, Korea. Carbon concentrations in tree components were significantly different among three tree species, except for roots and branches. Allometric equations for carbon storage using generalized method of moments with diameter at breast height (DBH) or DBH2 × height (H) as independent variables were significant in all three species with high coefficient of determination (R2 = 0.92 0.99). There was little difference of coefficient of determination and root mean squared errors (RMSE) between allometric equations using DBH and DBH2 × H as independent variables. Generalized allometric equations for foliage, branches and aboveground carbon storage for three tree species were significantly different (P < 0.05) in regression coefficients (slope). These results suggest that the accuracy of estimates for carbon storage of three tree species planted in an urban area could be improved by using species-specific carbon concentration and species-specific allometric equations.

This study compared carbon (C) and nitrogen (N) distribution at a stand level in an exotic Japanese cedar (Cryptomeria japonica D. Don) plantation and a natural Serrata oak (Quercus serrata Murray) stand growing under similar site conditions in South Korea. The aboveground biomass (stems, branches, and leaves) of 20 trees (10 of each species), the forest floor, and the mineral soils to a depth of 30 cm were sampled to determine C and N concentrations. Except in branches, C concentrations were significantly higher (p < 0.05) in the Japanese cedar plantation than in the Serrata oak stand, whereas N concentrations, except in the stem bark, were significantly lower in the Japanese cedar plantation. Reforestation with an exotic coniferous species significantly increased the C stocks in the aboveground biomass and the N stocks in the forest floor and mineral soils compared with a natural oak stand. The N stocks in the aboveground biomass were dependent on either the N concentrations or the C stocks in the tree components, whereas soil C and N stocks were negatively related to soil fertility parameters such as C/N ratio. Although it is uncertain which factors are responsible for the difference in aboveground C and soil N stocks following the establishment of Japanese cedar plantations on former natural Serrata oak stands, tree replacement may have an impact on C and N allocation within different forest compartments.

Changes in the abiotic and biotic factors created by forest regeneration can have a major influence on soil respiration, which is an important component of the forest carbon (C) cycle. This study was performed to determine the soil respiration rates caused by regeneration approaches in Chamaecyparis obtusa planted in pine wilt disease (PWD)-disturbed stands in South Korea. In 2007, four-year-old C. obtusa seedlings were planted with two regeneration approaches, clearcutting (CS) of infected pine trees or underplanting following selective cutting (DS) of infected pine trees in disturbed pine stands. Soil respiration rates were assessed in two regeneration approaches and an undisturbed pine stand (NS) for two years. The mean soil respiration rates were significantly lower in the DS (1.07 µmol m⁻² s⁻¹) treatment than in the NS (1.87 µmol m⁻² s⁻¹) treatment, whereas there was no significant difference between the CS (1.44 µmol m⁻² s⁻¹) treatment and the NS or DS treatment. The three treatments showed exponential relationships between soil respiration rates and soil temperature (R² = 0.57–0.81). The annual soil respiration rates were significantly higher in the CS (6.49 Mg C ha⁻¹ year⁻¹) treatment than in the DS (3.98 Mg C ha⁻¹ year⁻¹) treatment. The Q₁₀ values were lowest in the DS (2.00–2.03) treatment, followed by the CS (2.23–2.62) and NS (2.74–3.07) treatments. These results reveal that DS approaches in PWD-disturbed stands are one for the critical drivers of reducing annual soil respiration rates.

Compound fertilizer is generally applied to alleviate multi-nutrient deficiency problems in forest stands, but research on the effect of fertilizer application on soil CO₂ efflux (Rs) processes has focused on the role of single-nitrogen (N) application. This study evaluates the effects of N addition in compound fertilizer on the rates in Pinus densiflora S. et Z. (Korean red pine) stands. Compound fertilizer with N (N₃P₄K₁ = 113:150:37 kg ha⁻¹ yr⁻¹) and without N (P₄K₁ = 150:37 kg ha⁻¹ yr⁻¹) was applied on the forest floor for three years. Rs rates were measured for four years, from April 2011 to March 2015. The mean annual Rs rates during the study period were 3.10 µmol m⁻² s⁻¹ in the N₃P₄K₁, 3.08 µmol m⁻² s⁻¹ in the P₄K₁, and 3.08 µmol m⁻² s⁻¹ in the control treatment. The rates in all treatments were significantly lower in 2013 (2.73 µmol m⁻² s⁻¹) than in other sampling years (3.03–3.58 µmol m⁻² s⁻¹) when the mean soil water content was the lowest (15.7%) during the four sampling years (other sampling years: 23.0–24.1%). The exponential relationships between Rs and the soil temperature were slightly more significant in the fertilized (N₃P₄K₁: R² = 0.72–0.80; P₄K₁: R² = 0.70–0.81) treatments compared to the control (R² = 0.62–0.74) treatment. The mean Q₁₀ values for the four years were similar between the N₃P₄K₁ treatment (4.19), the control (4.23) treatment, and the P₄K₁ (4.24) treatment. The results demonstrate that mean annual Rs rates in Korean red pine stands were not affected by the increased N availability in compound fertilizer, whereas decreases in mean annual Rs rates may be strongly attributed to the soil water content.