Sue Kyoung Lee

Carbon and nitrogen storage in an age-sequence of Pinus densiflora stands in Korea

The carbon (C) and nitrogen (N) storage capabilities of Pinus densiflora in six different stand ages (10, 27, 30, 32, 44, and 71 years old) were investigated in Korea. Thirty sample trees were destructively harvested and 12 were excavated. Samples from the above and belowground tree components, coarse woody debris (CWD), forest floor, and mineral soil (0–30 cm) were collected. Tree biomass was highest in the 71-year-old stand (202.8 t ha−1) and lowest in the 10-year-old stand (18.4 t ha−1). C and N storage in the mineral soil was higher in the 71-year-old stand than in the other stands, mainly due to higher soil C and N concentrations. Consequently, the total ecosystem C and N storage (tree+forest floor+CWD+soil) was positively correlated with stand age: increasing from a minimum in the 10 year old stand (18.8 t C ha−1 and 1.3 t N ha−1) to a maximum in the 71-year-old stand (201.4 t C ha−1 and 8.5 t N ha−1). The total ecosystem C storage showed a similar sigmoidal pattern to that of tree C storage as a function of the age-sequence, while N storage in the CWD, forest floor and mineral soil showed no significant temporal trends. Our results provide important insights that will increase our understanding of C and N storage in P. densiflora stands and our ability to predict changes according to stand age in the region.

Coarse woody debris mass dynamics in temperate natural forests of Mt. Jumbong, Korea

Coarse woody debris (CWD) mass dynamics in three temperate natural forests, dominated by Quercus mongolica, Ab- ies holophylla, and Pinus densiflora, were studied for 5 to 8 years in a Korea National Long-Term Ecological Research (KNLTER) site located in Mt. Jumbong, Korea. CWD mass (Mg/ha), input rate of CWD mass (Mg ha -1 y -1 ), and decay rate constant (1/y) were 20.6, 1.20, and 0.058 for Q. mongolica forest, 12.2, 0.44, 0.106 for A. holophylla forest, and 5.0, 0.00, and 0.086 for P. densiflora forest, respectively. CWD mass was classified into species, types (log, snag, and stump), and decay classes (I-V). The proportion of logs was higher than that of the other CWD types in Q. mongolica forest because of wind-related mortality, whereas the proportion of logs was similar to the proportion of snags in A. holophylla forest and P. densiflora forest. CWD mass, input rate, decay rate, and distribution reflected the status of forest regeneration and succession for three forests. Mass dynamics were affected interactively by a variety of factors including species, micro- climate, and topography, but these effects were hardly distinguishable in this study because of the limited number of comparable sites and pieces of CWD. Thus, further studies will require data regarding long-term microclimate and CWD mass dynamics in a variety of forest types, which could represent diverse environmental factors.

Influence of thinning on carbon storage in a Japanese larch (Larix kaempferi) plantation in Yangpyeong, central Korea.

This study was conducted to determine the carbon (C) contents in a Japanese larch (Larix kaempferi) plantation with four different thinning intensities over 12 years in Yangpyeong, central Korea. Thinning was applied in April of 1997 [control, no thinning (2250 trees/ha)], light thinning (T10, 10% thinning, 2000 trees/ha after thinning), moderate thinning (T20, 20%thinning, 1750 trees/ha after thinning), and heavy thinning (T40, 40% thinning, 1200 trees/ha after thinning)]. We measured individual tree DBH (cm) in November, 2009 and calculated biomass using the allometric regression equation. Forest floor (litter and coarse woody debris (CWD)) and soils, litter and soils up to 30 cm were collected and analyzed. Even though tree survival rate during 12 years was highest in the heavy thinning plot (T40), vegetation C content (Mg C/ha) was significantly higher in the light thinning plot (T10) than the other plots: 58.5 for control, 64.9 for T10, 60.4 for T20, and 55.8 for T40, respectively. Moreover, total soil C content (Mg C/ha) was higher in the moderate thinning plot (T20), however, there was no significant difference among the other plots; 56.2 for control, 57.8 for T10, 63.7 for T20, and 62.3 for T40. C contents of forest floor (litter plus CWD) were largest in the control plot, which might be influenced by the individual tree species competition; 11.9 for control, 10.2 for T10, 10.1 for T20, and 6.6 for T40, respectively. Total ecosystem C content was higher in the moderate thinning plot (T20) than those in other thinned and unthinned plots: 125.2 for control, 131.2 for T10, 132.4 for T20, and 125.9 for T40, respectively. Moderate thinning treatment (T20) seemed more effective to conserve total ecosystem C content while the individual tree growth (mean DBH and height) was higher in the heavy thinning plot (T40).

Effect of thinning on carbon storage in soil, forest floor and coarse woody debris of Pinus densiflora stands with different stand ages in Gangwon-do, central Korea

This study was conducted to investigate effects of thinning on carbon (C) storage of soil, forest floor and coarse woody debris (CWD) in Pinus densiflora stands, central Korea. Two study stands (25- and 55-year-old stands) were located in P. densiflora forests of Gangwon-do and thinned in 2008. Each stand was divided into three plots by different thinning intensities based on stand density: no thinning (control, 0%), moderate thinning (M, 30%), and heavy thinning (H, 50%) in the 25-year-old stand and no thinning (control, 0%), light thinning (L, 20%), and moderate thinning (M, 30%) in the 55-year-old stand. We measured C storage of 0–30 cm depth soil, forest floor and CWD in 2009. Total C storage (t C ha−1) of soil, forest floor and CWD in two thinned plots was significantly higher than that in the control plot only in the 55-year-old stand: 66.4 for control, <84.2 for L, <117.9 for M. On the other hand, total C storage in the 25-year-old stand did not show a consistent tendency among thinning intensities. We speculated that 1 year was too short to detect any consistent changes in total C storage of soil, forest floor and CWD by thinning, and long-term observation would be needed.

Carbon Storage of Pure and Mixed Pine-Deciduous Oak Forests in Gwangneung, Central Korea

This study was conducted to determine the carbon (C) contents in different mixed stands of P. densiflora and deciduous oak species in Gwangneung, central Korea. Five mixed stands with different ratios of P. densiflora and deciduous oak species were chosen based on the basal area of all trees ≥5 cm DBH: pure P. densiflora (P100D0), 70% P. densiflora+30% deciduous oak species (P70D30), 44% P. densiflora+56% deciduous oak species (P50D50), 37% P. densiflora+63% deciduous oak species (P40D60), and 10% P. densiflora+90% deciduous oak species (P10D90). Total C contents in the overstory (aboveground and belowground) vegetation were higher in the mixed stands (P70D30, P50D50, P40D60) than in the pure stands (P100D0, P10D90). Moreover, except for P40D60, C contents of forest floor (litter and coarse woody debris) were larger in the mixed stands (P70D30, P50D50) than in the pure stands. However, total soil C contents up to 30cm depth were highest in the pure deciduous oak stand than in the pure P. densiflora stand and mixed stands. Total ecosystem C contents (Mg/ha) were 163.3 for P100D0, 152.3 for P70D30, 188.8 for P50D50, 160.2 for P40D60, and 150.4 for P10D90, respectively. These differences in total ecosystem C contents among the different mixed stands for P. densiflora and deciduous oak species within the study stands were attributed by the differences in vegetation development and forest management practices. Among the five study stands, the total ecosystem C contents were maximized in the 1:1 mixed ratio of P. densiflora and deciduous oak species (P50D50).

Diurnal pattern of soil CO2 efflux in a pinus densiflora forest measured using an open‐flow chamber system

This study was conducted to investigate the diurnal pattern of soil CO2 efflux (RS) using an open‐flow, closed‐chamber system for a 70‐ to 80‐year‐old Pinus densiflora forest in the Gwangneung Experimental Forest in central Korea. The daily mean RS rate (g CO2 m-2 h-1) was 0.486 in September, 0.073 in April, and 0.169 in May 2010. Although RS exhibited a diurnal pattern that was similar to the soil temperature pattern, the pattern varied seasonally. The Q10 value was 4.57 and 4.26 for day and night time, respectively. The annual RS rate was estimated as 6.16 t C ha-1 y-1 by the relationships between RS and soil temperature using continuous measurements, but as 6.73 t C ha-1 y-1 by using the 11:00 h mid‐morning point measurements. Our study results demonstrate the necessity of measuring the diurnal pattern of RS throughout the whole year in order to obtain an accurate estimate of annual RS using an open‐flow, closed‐chamber system.

Changes in soil properties of Abies holophylla and Quercus-dominated stands 4 years after trenching

Abstract Few studies tried to isolate the influence of plant roots on the soil characteristics including soil carbon (C) and nitrogen (N) storage. We evaluated the impact of root trenching on soil characteristics of coniferous (Abies holophylla) and deciduous (Quercus spp.) stands 4 years after trenching. Trenching treatment significantly increased the soil water content and nitrate concentration in both stand types. Soil pH, cation exchange capacity, soil C and N pools and isotopic compositions of C and N were significantly different between two stands, but trenching was not found to have significant impact on these soil properties. Our results indicated that root trenching in coniferous and broad-leaved deciduous forests of temperate region could significantly alter soil moisture regime and inorganic N levels, but not C and N stabilization in soils.

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.

Short-term effect of thinning on carbon storage in soil, forest floor and coarse woody debris of Quercus spp. stand in Hoengseong, Gangwon-do, Korea

This study was conducted to investigate the short-term effect of thinning on the carbon (C) storage of soil, forest floor and coarse woody debris (CWD) in a Quercus spp. stand in Hoengseong, Gangwon-do, Korea. Thinning was conducted in March 2010 with different thinning intensities based on the removed volume in each plot: no thinning (control, 0%), light thinning (L, 15%), moderate thinning (M, 20%), and heavy thinning (H, 35%). We measured the C storage at four different depths ranging from 0–50 cm, on the forest floor and in CWD four months after thinning in July 2010. The total C storage (Mg C ha−1) in soil, forest floor and CWD of L was significantly lower than that of the three other plots at an early stage of thinning: 38.5 for control, 31.1 for L, 40.6 for M and 45.8 for H. Further long-term monitoring will be needed to observe the total C storage in soil, forest floor and CWD in this study stand because the total C storage with different thinning intensities might vary temporally.