Don Koo Lee

Assessment of Pb uptake,translocation and immobilization in kenaf (Hibiscus cannabinus L.) for phytoremediation of sand tailings

The potential of kenaf (Hibiscus cannabinus L.) for phytoremediation of lead (Pb) on sand tailings was investigated. A pot experiment employing factorial design with two main effects of fertilizer and lead was conducted in a nursery using sand tailings from an ex-tin mine as the growing medium. Results showed that Pb was found in the root, stem, and seed capsule of kenaf but not in the leaf. Application of organic fertilizer promoted greater biomass yield as well as higher accumulation capacity of Pb. In Pb-spiked treatments, roots accumulated more than 85% of total plant Pb which implies that kenaf root can be an important sink for bioavailable Pb. Scanning transmission electron microscope (STEM) X-ray microanalysis confirmed that electron-dense deposits located along cell walls of kenaf roots were Pb precipitates. The ability of kenaf to tolerate Pb and avoid phytotoxicity could be attributed to the immobilization of Pb in the roots and hence the restriction of upward movement (translocation factor < 1). With the application of fertilizer, kenaf was also found to have higher biomass and subsequently higher bioaccumulation capacity, indicating its suitability for phytoremediation of Pb-contaminated site.

Changes of net photosynthesis, antioxidant enzyme activities, and antioxidant contents of Liriodendron tulipifera under elevated ozone

Liriodendron tulipifera was exposed to gradually elevated ozone concentrations of 100–300 μg kg−1 in the naturally irradiated environment chamber. During 15 d of exposure to O3, net photosynthetic rate (PN) decreased and there was large difference between the control (C) and treatment with ozone (OT), while there was no significant difference in water use efficiency. Total chlorophyll content as well as the value of fluorescence parameter Fv/Fm decreased, while antioxidant enzyme activities related to ascorbate-glutathione cycle increased after 15 d of OT. Unchanged contents of ascorbate and glutathione indirectly suggest that the species hastened the antioxidant’s oxidization/reduction cycle using enzymes instead of expanding their pool against oxidative stress.

Net photosynthetic rate, ascorbate peroxidase and glutathione reductase activities of Erythrina orientalis in polluted and non-polluted areas

We investigated net photosynthetic rate and antioxidative enzyme activities in Erythrina orientalis grown in three different sites: Makati and Quezon (cities with high levels of air pollution, HP) and La Mesa (a non-polluted area, NP). Photosynthetic activity of E. orientalis was significantly reduced in the HP cities. In contrast, activities of the antioxidative enzymes ascorbate peroxidase and glutathione reductase were significantly higher in HP cities than in the NP area.

Stand structure and regeneration of Quercus mongolica forests in Korea

This study was conducted to analyze the stand structure of Quercus mongolica forests in Korea and to understand their regeneration dynamics. Forest community types of Mt. Joongwang, Mt. Chiri and Mt. Worak were classified into 7 groups by TWINSPAN. Q. mongolica appeared mainly on mid to upper slope positions. Acer mono, A. pseudo-sieboldianum, Maackia amurensis and Tilia amurensis are commonly associated with Q. mongolica. The density and basal area of Q. mongolica decreased as the stand developed into pole and early-mature stage forests. Total number of species increased as stands developed. Q. mongolica is an early invader of disturbed areas and dominates the stand, which means that this species should be considered as a pioneer species rather than a climax. Germination rate of scattered acorns was very low but fallen leaves over the acorns protected them from animal feeding and raised the germination rate. Among the seedlings of Q. mongolica, more than 70% originated from seedling sprouts. They showed a higher growth potential than seedlings, and their heartwoods are decay resistant. Therefore, their number and size were very important factors in determining the species composition of future forests after clearcutting.

Effect of Land Cover Change on Soil Phosphorus Fractions in Southeastern Horqin Sandy Land, Northern China

In the past 50 years, large areas of the Horqin sandy land were afforested to prevent desertification. Although the afforestation policy appears successful, many people now doubt whether it is suitable to plant trees with high density on the poor soils in semiarid regions. Little is known about the impacts of afforestation on the sandy soil properties, although the evaluation of these impacts is fundamental to judge the rationality of afforestation policy. Soil phosphorus (P) fractions, acid phosphomonoesterase activities, and other soil chemical properties were compared among five adjoining typical ecosystems on poor sandy soils in southeastern Horqin sandy land. The ecosystems studied are natural elm savanna, degraded grassland, Mongolian pine (Pinus sylvestris var. mongolica) plantation, Chinese pine (Pinus tabulaeformis) plantation, and mixed plantation of Mongolian pine and poplar (Populus simonii). The results showed that organic P dominated soil P (47%-65%) was the principal source of available P. The degradation of elm savanna to grassland significantly reduced soil pH and resulted in an overall reduction in soil fertility, although slightly increased labile inorganic P. Grassland afforestation had no significant influence on soil pH, organic carbon, and total N but significantly reduced total P. Impacts of grassland afforestation on soil P fractions depended on tree species. Natural elm savanna had higher soil P conserving ability than artificial plantations. Therefore, with the aim of developing a sustainable ecosystem, we suggested that vegetations with low nutrient demand (particularly P) and efficient nutrient cycling would be more suitable for ecosystem restoration in the semiarid region.

Induction of neurite outgrowth by (-)-(7R, 8S)-dihydrodehydrodiconiferyl alcohol from PC12 cells.

A lignan derivative, (-)-(7R, SSJ-dihydrodehydrodiconiferyl alcohol (DHDA), was isolated fromKalopanax septemlobus L. and was observed to have neuritogenic activity. DHDA at 50 μ? caused a marked induction of neurite outgrowth and an enhancement of nerve growth factor (NGF)-mediated neurite outgrowth from PC12 cells. However, it did not exhibit any neu-rotrophic action. At 50 μ?, DHDA enhanced NGF-induced neurite-bearing activity. This activity was partially blocked by the mitogen-activated protein kinase inhibitor PD98059 and by GF109203X, a protein kinase inhibitor. These results suggest that DHDA can induce neurite outgrowth and enhance NGF-induced neurite outgrowth from PC12 cells by amplifying up-stream steps such as and PKC.

Minimizing nutrient leaching and improving nutrient use efficiency of Liriodendron tulipifera and Larix leptolepis in a container nursery system

Fertilization is essential to seedling production in nursery culture, but excessive fertilization can contaminate surface and ground water around the nursery. The optimal fertilization practice is that which maximizes seedling growth and minimizes nutrient loss. We tested three fertilization strategies: (1) constant fertilization (2) a three-stage rate, and (3) exponential fertilization on Liriodendron tulipifera and Larix leptolepis containerized seedlings. Growth performance, nutrient uptake, and nutrient loss in leaching were measured. Height, root collar diameter, and dry weight of both species were not significantly different among treatments even though the nutrient supply of the exponential treatment was half that of the constant and three-stage treatments. Generally, nutrient losses in leached solutions were higher in constant and three-stage than the exponential treatment. Nutrient use efficiency was calculated as the ratio of the nutrient content of the seedlings to the amount of nutrient applied to the containers. The nitrogen use efficiency in the constant, three-stage, and exponential treatments was 63, 61, and 85% for yellow poplar, respectively, and 35, 30, and 53% for larch. Similar results were obtained for phosphorus and potassium. Thus, the exponential treatment had the highest nutrient use efficiency as well as the least nutrient loss. Adjusting fertilization rates can reduce soil and water contamination around the nursery without compromising growth performance, which reduces both producer’s investments and environmental impacts.

Micromorphology of epicuticular waxes and epistomatal chambers of pine species by electron microscopy and white light scanning interferometry.

High-resolution imaging and quantitative surface analysis of epicuticular waxes and epistomatal chambers of pine species were performed by field emission scanning electron microscopy and white light scanning interferometry. Both juvenile and adult needles were collected from the two-year-old seedlings of Pinus rigida and Pinus densiflora and subjected to surface observations. Epicuticular wax structures developed on the cuticle layer as well as in the epistomatal chambers and appeared to occlude the cavities in the two pine species. The stomata of P. densiflora were characterized by more distinctly raised rings around openings than P. rigida. The most common epicuticular wax structures of the two pine species included tubules with terminal openings and coiled rodlets. Wax platelets were deposited on epistomatal chambers. Either rodlets or tubules seemed to be longer and thicker in P. rigida than those in P. densiflora. White light scanning interferometry revealed quantitative surface profiles, demonstrating more ridged (ca. 4 μm high) stomatal apertures and nearly twofold deeper (ca. 20 μm deep) epistomatal chambers of P. densiflora than those of P. rigida. These results suggest that white light scanning interferometry can be applied to unravel the quantitative surface features of epicuticular sculptures on plant leaves.

Roles of Saemaul Undong in Reforestation and NGO Activities for Sustainable Forest Management in Korea

Abstract The forests in Korea cover 6.4 million ha, which is about 65 percent of the total land area. During the Japanese occupation in World War II and the Korean War, forest resources were severely exploited due to illegal cutting and shifting cultivation. A substantial amount of fuelwood was required for heating and cooking in the 1950s and 1960s. Due to the great demand for fuel energy, the Korean Government established 643,000 ha with fast-growing trees such as Pinus rigida, Robinia pseudo-acacia, Alnusspp., and Quercus acutissimafrom 1967 to 1977. Also, the Government initiated the first 10-year Forest Development Plan for Rehabilitation and Restoration in 1973. As a result, the growing stock is 70 m3/ha as of 2002. Successful reforestation of degraded forest areas not only resulted in the massive implementation of forest plans but led to the new community movement called “Saemaul Undong (SU).” Saemaul Undong began in 1970 and can be defined as a systematic movement that promotes the following factors: (1) education to expand latent human ability, (2) the environmental factor, to change the environment to improve oness living conditions, (3) the social factor, to provide more opportunities for becoming financially self-sufficient, and (4) the creative powers of human beings. During 1997–2001, unemployment in Korea was high due to IMF restructuring. As a way of reducing unemployment, forest tending programs have been applied through Forest for Life (FFL) campaign since 1998. Up to 2001, the programs provided US

Effect of Acacia plantations on net photosynthesis, tree species composition, soil enzyme activities, and microclimate on Mt. Makiling

400 million to tend 383,000 ha of forest areas, as well as new jobs, which in turn has contributed to sustainable forest management.