Hoonbok Yi

Response of Ground-Dwelling Arthropods to Different Thinning Intensities in Young Douglas Fir Forests of Western Oregon

Abstract We evaluated the effect of four different forest management techniques, unthinned control and three thinning intensities (light, light with gaps, and heavy thin), on arthropod abundance, diversity, and community structure as an indicator of ecological processes affecting other forest fauna. Ground-dwelling arthropods were collected during 2000–2001, with pitfall traps in June (warm-wet season) and August (hot-dry season) 5 yr after a thinning treatment in 40- to 60-yr-old Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] trees in the Willamette National Forest. We found arthropod abundance and diversity was higher in heavy and light/gap thinning treatments than the other treatments. Additionally, four groups (ants, spiders, camel-crickets, and millipedes) preferred the more intense thinning treatment areas. The abundance of carabids, the third most abundant group, was higher at the unthinned control than any thinning treatment during the wet season, but not during the dry season. Although the immediate disturbance associated with thinning might be expected to decrease population density of fauna such as ground beetles, we hypothesized that the principal effect of thinning was to increase habitat heterogeneity in these uniform plantations and indirectly increase species richness and abundance of soil-dwellers. Nonmetric multidimensional scaling (NMS) of overall arthropod community composition revealed that both seasonality and thinning were highly significant, resulting in four separate clusters of points, with season dominating thinning. Both variables were correlated with litter moisture. The NMS results indicated that ants preferred heavy thinning intensity. Spiders, carabids, and millipedes were positively associated with litter moisture, and camel-crickets were negatively associated with litter moisture. Overall, our results suggest that some dominant groups of ground-dwelling arthropods are sensitive indicators of environmental change, such as forest thinning.

Responses of Litter-Dwelling Arthropods to four Different Thinning Intensities in Douglas-Fir Forests of the Pacific Northwest, USA

We investigated the response of litter-dwelling arthropods to the effects of four forestry thinning intensities (Control, Light Thin, Light Thin with Gap, and Heavy Thin). With the balance between timber demand and maintaining biodiversity in the forest ecosystem in mind, we examined the effects of thinning on the abundance, richness, and diversity of arthropods as an indicator of how ecological processes affect forest litter-dwelling fauna. Study sites were 40- to 60-year-old stands of typical Douglas-fir plantation in the Willamette National Forest, Oregon, USA. To examine the seasonal response of the litter-dwelling arthropods, litter debris and humus samples were collected in October 2000 (wet late-growing season, Late 2000), June 2001 (wet early-growing season, Early 2001), and August 2001 (dry mid-growing season, Mid 2001) and extracted with Tullgren funnels. The abundance and diversity of litter-dwelling arthropods decreased as thinning intensity increased. The decreases in both abundance and diversity of arthropods with limited mobility within the two heaviest thinnings were correlated with an increased heterogeneity of disturbance to the forest floor (patchy litter and moss cover removal), rather than responses to thinning itself at the scale of the entire stand. The litter-dwelling fauna correlated positively with litter moisture. Under control conditions, the abundance of predators and detritivores increased during the dry summer in August. Non-metric multidimensional scaling results showed distinct clusters for the three growing seasons. The wet early-growing season clustered with the dry mid-growing season, but not with the wet late-growing season. Moisture correlated highly with the ordination axes. This study showed that litter-dwelling arthropods were correlated with stand density and seasonal litter moisture of the forest floor.

Detection of gene flow from GM to non-GM watermelon in a field trial

Gene flow from genetically modified (GM) crops to conventional non-GM crops is a serious concern for protection of conventional and organic farming. Gene flow from GM watermelon developed for rootstock use, containing cucumber green mottle mosaic virus (CGMMV)-coat protein (CP) gene, to a non-GM isogenic control variety “Clhalteok” and grafted watermelon “Keumcheon” was investigated in a small scale field trial as a pilot study. Hybrids between GM and non-GM watermelons were screened from 1304 “Chalteok” seeds and 856 “Keumcheon” seeds using the duplex PCR method targeting theCGMMV- CP gene as a marker. Hybrids were found in all pollen recipient plots. The gene flow frequencies were greater for “Chaiteok” than for “KeumcheonD; with 75% outcrossing in the “Chaiteok” plot at the closest distance (0.8 m) to the GM plot. A much larger scale field trial is necessary to identify the isolation distance between GM and non-GM watermelon, as the behaviors of insect pollinators needs to be clarified in Korea.

Effect of thinning on flying insect communities using window traps in young douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests in the Pacific Northwestern America

The response of insects to four thinning intensities (control, light-thin, heavy-thin, or light-thin with gaps) was examined in 40-to 60-year-old Douglas-fir stands on the Willamette National Forest in Oregon, USA. In both 2000 and 2001, flying insect assemblages were collected from window traps placed over the forest floor in the center of each treatment block during two annual intervals: 1 ) June through August (early-season) and 2) August through October (late-season). The seasonal responses by these insects showed statistically significant differences in species richness (F= 22.21,P <0.001) and mean abundance (F=34.87,P <0.001). The greatest numbers of taxa generated via indicator species analysis were in the early season and within the treatment of light-thin with gap (L./ G). In particular, the woodborer beetle,Buprestis (Burprestidae), was strongly associated with L/G (Indicator Value = 52.4, P ≤0.001 ). Two beetle taxa,Ampedus (Elateridae, IV=84.7, P ≤0.001 ) and members of Cermabycidae (IV=58.4, P ≤0.001 ), were correlated significantly with early-season, whereasMelanoplus (Acrididae) was associated with late-season (IV=21.3, P >0.05) and L/G (IV=29.2, P ≤0.05). For all thinning treatments, the numbers of species and individuals were higher in the early season than the late season. Non-metric multidimensional scaling showed that Axis 1 (65%) and Axis 2 (27%) explained 92% of the variance. The former was strongly associated with thinning intensity, having higher coefficients of species richness (r=0.645) and species diversity (r=0.583). The multi-response permutation procedures showed a statistically significant difference for thinning intensity (T-statistics=-4.6322,A-statistics=0.0479,P <0.0001 ). These results suggest that heavier thinning can result in more diverse populations of flying insects, including herbivores and predators.

Assessment of the Persistence of DNA in Decomposing Leaves of CMVP0-CP Transgenic Chili Pepper in the Field Conditions

This study was conducted to evaluate the persistence of DNA in the transgenic chili pepper resistant to cucumber mosaic virus (CMV) in the field condition. We analyzed the persistence of genes in the leaf samples obtained from two field conditions, below and above soil. Transgenic and non-transgenic leaf tissues were buried in the soil at a depth of 10 cm or placed on the soil surface. Qualitative and quantitative PCR analysis showed that the amount of transferred genes from the transgenic peppers below and above soil was dropped to 28.3-42.7% one month after buried and it was rapidly reduced to 0.9-3.3% after two months. The transgenes were not detected three to four month after buried. In addition, DNA of the leaves placed below soil decomposed about 8%more than those on soil surface. The gene transfer from decomposing leaves of the transgenic pepper to soil was investigated by PCR analysis with the soil attached to the samples. The PCR result indicated that the gene transfer from the transgenic pepper to soil was not occurred.

The Effect of the Anthracnose Resistant Chili Pepper (PepEST gene) on the Non-target Insects, Green Peach Aphids (Myzus persicae Sulzer, Homoptera)

To assess the environmental risks of transgenic chili pepper with PepEST gene on non-target organisms before it exposes to the agro-ecosystem environments, we conducted the three sets of green peach aphids (Myzus persicas S.) life table experiment under laboratory conditions (Temp. , R.H. 50-70%, Photoperiod L16 : D8) in series during 2005-2006. We measured the net reproductive rate (, the intrinsic rate of increase (), the mean generation time (), , life span, and reproduction period between non-transgenic chili peppers and transgenic chili peppers, respectively. The life span of green peach aphids from three sets was 31, 27, 25 days, and the period of life span was similar to the general average length of green peach aphids, 25-29 days. Although the first reproduction of transgenic pepper was similar to the non transgenic pepper (P>0.05), the fecundity and the net reproductive rate () by using Jackknife method of transgenic pepper were lower than those of non transgenic pepper (P

Changes in lipoxygenase properties and activity related to postgerminative growth and senescence in oat (Avena sativa L cv. Victory 1 )

Lipoxygenase (LOX), one of the main oxidative catalysts in plants, is involved in the regulation of growth and senescence. We investigated changes in LOX activity or its properties as they related to the development of oat plants at four stages (germination, growth, natural senescence, and dark-incubated senescence). LOX activity was high during early growth and at senescence. At pH 4.5, activity showed an abrupt surge compared with a normal enzyme reaction pattern at pH 6.5. The optimum reaction temperature was 25°C; LOX and peroxidase exhibited similar activity patterns. Polyacrylamide gel electrophoresis revealed that the purified LOX consisted of three isoenzymes in germinating seeds, two in growing seedlings, and three during both natural and dark-induced senescence. As determined by isoelectric focusing, the isoelectric points (pl) of LOX ranged from 3.6 to 6.5 throughout the four developmental stages; for natural or dark-induced senescence, the pl was 9.0.

The Growth Response of Quercus dentata Sapling to the Environmental Gradients Treatment

Quercus dentata (Thunb. ex Murray) is a major tree found in dry habitats such as limestone areas of Korea. In order to characterize the ecological traits of Q. dentata, we treated Q. dentata saplings under four gradient levels of major environment factors such as light, soil moisture and nutrients for 5 months in a glass house. We then measured and analyzed growth differences among them. Regarding light, aboveground, belowground and plant biomass were highest at a high gradient and lowest at a low one. The root/shoot ratio was highest at the highest light gradient. Regarding moisture, no measured items were significantly affected by the moisture gradient. Regarding nutrients, above-ground, belowground and plant biomass were the highest at a slightly high gradient and the lowest at a gradient lower or higher than this. The root/shoot ratio was not significantly affected by the nu-trient gradient. From these results, it was shown that the growth of Q. dentata was more affected by light and nutrients in the environment than moisture.Keywords : Quercus, ecological trait, environmental treatment