Youngil Kim

Effect of inundation, oxygen and temperature on carbon mineralization in boreal ecosystems

The inundation of boreal forests and peatlands through the construction of hydroelectric reservoirs can increase carbon dioxide (CO2) and methane (CH4) emission. To establish controls on emission rates, we incubated samples of forest and peat soils, spruce litter, forest litter and peatland litter collected from boreal ecosystems in northern Quebec for 16 weeks and measured CO2 and CH4 production rates under flooded or non-flooded conditions and varying oxygen concentration and temperature. CO2 production under flooded conditions was less than under non-flooded conditions (5-71 vs. 5-85 mg Cg(-1) C), but CH4 production under flooded conditions was larger than under non-flooded conditions (1-8158 vs. 0-86 μg Cg(-1) C). The average CO2 and CH4 production rate factor for flooded:non-flooded conditions was 0.76 and 1.32, respectively. Under flooded conditions, high oxygen concentrations increased CO2 production in peat soils but decreased CH4 production in forest and peat soils and spruce litter. Warmer temperatures (from 4 to 22°C) raised both CO2 production in peat soils and peatland litter, and CH4 production in peat soils and spruce litter. This study shows that the direction and/or strength of CO2 and CH4 fluxes change once boreal forests and peatlands are inundated.

Inter-annual and inter-plot variations of wood biomass production as related to biotic and abiotic characteristics at a deciduous forest in complex terrain, Korea

This study aims to evaluate inter-annual and inter-plot variation of wood biomass production (WBP) and to investigate the relationships of the WBP variations with several biotic and abiotic characteristics at a deciduous forest in complex terrain, the Gwangneung Experimental Forest, Korea. Based on field survey in the plot-scale study area, WBP during 1991–2004 was estimated by a dendrochronological method. Our field data indicated that the inter-annual variation of WBP was closely related to the seasonal climate of both winter air temperature and spring precipitation. The inter-plot variation of WBP was highly associated with basal area, biomass, and frequency of Quercus spp. in the plots, and correlations of the inter-plot variation with the stand characteristics of the specific species were stronger than those with slope and soil water content. Our results suggest that the annual fluctuation of forest productivity is primarily governed by severe climate in a season of the year, and the spatial distribution of a dominant species largely represent plot variation in the productivity. Our findings contribute to an enhanced understanding of climatic effects on the annual variability of forest productivity and the spatial heterogeneity of the productivity, which are extensively concerned with forested ecosystems of Korea.

Introducing a sensor to measure budburst and its environmental drivers

Budburst is a key adaptive trait that can help us understand how plants respond to a changing climate from the molecular to landscape scale. Despite this, acquisition of budburst data is constrained by a lack of information at the plant scale on the environmental stimuli associated with the release of bud dormancy. Additionally, to date, little effort has been devoted to phenotyping plants in natural populations due to the challenge of accounting for the effect of environmental variation. Nonetheless, natural selection operates on natural populations, and investigation of adaptive phenotypes in situ is warranted and can validate results from controlled laboratory experiments. To identify genomic effects on individual plant phenotypes in nature, environmental drivers must be concurrently measured, and characterized. Here, we designed and evaluated a sensor to meet these requirements for temperate woody plants. It was designed for use on a tree branch to measure the timing of budburst together with its key environmental drivers; temperature, and photoperiod. Specifically, we evaluated the sensor through independent corroboration with time-lapse photography and a suite of environmental sampling instruments. We also tested whether the presence of the device on a branch influenced the timing of budburst. Our results indicated the following: the temperatures measured by the budburst sensor’s digital thermometer closely approximated the temperatures measured using a thermocouple touching plant tissue; the photoperiod detector measured ambient light with the same accuracy as did time lapse photography; the budburst sensor accurately detected the timing of budburst; and the sensor itself did not influence the budburst timing of Populus clones. Among other potential applications, future use of the sensor may provide plant phenotyping at the landscape level for integration with landscape genomics.