Range-wide genetic variation of Korean pine (Pinus koraiensis) was assessed using maternally inherited mtDNA and paternally inherited cpDNA for 16 natural populations throughout northeast Asia in order to study its phylogeographical history during the Quaternary. The cpDNA variation indicated that there was no difference between populations on the Asian continent and those in the Japanese archipelago. In contrast, the mtDNA variation indicated that there was significant difference between the populations from the two regions, with each region having a different lineage. The continental populations exhibited no diversity in the mtDNA examined despite the species' current extensive range and large populations. Conversely, while the Korean pine is rare in Japan, the Japanese populations exhibited greater levels of mtDNA diversity (H (T) = 0.502). The higher mtDNA diversity and evidence from numerous Korean pine macrofossil remains dated to the Pleistocene and recovered various sites in Japan suggest that the Japanese archipelago once served as a refugium to a much larger Korean pine population with a more extensive range than is the case today. The presence of the single mtDNA haplotype across the Asian continent suggests that the present widespread populations could have expanded from a single refugium population after the last glacial periods.

We measured photosynthetically active radiation (PAR) beneath the forest canopy, understory species' richness and diversity, and biomass in a Larix leptolepis plantation in central Korea 4 years after thinning. Four different thinning intensities (control, 10%, 20%, and 40% stocking reduction) were applied in 1997. Mean annual intercepted PAR at 30 cm and 1 m above ground level was significantly different among the thinning intensities and strongly correlated with the number of stems remaining after thinning. Understory species richness and diversity were lowest in the unthinned stands and increased with thinning intensity, and there were significant correlations between the total number of understory species or diversity index (Shannon's diversity index, HЈ) and the number of stems per hectare after thinning. Also understory above-ground biomass was significantly increased with thinning intensity in both sampling months (June and August 2001). Thinning increased light inputs to the ground and resulted in higher species richness and diversity and above-ground biomass. These results suggested that light availability and understory responses to thinning at a comparable intensity are likely to last well beyond the 4 years of this study.

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The amount and distribution of genetic diversity within and between Megaleranthis saniculifolia Ohwi populations were compared between the central and peripheral regions of the species distribution. Allozyme and ISSR markers were used for genetic analysis of six populations from the central region (DY) and five populations from the peripheral region (MJ). Genetic diversity was substantially higher in the DY region than in the MJ region. Relatively uniform homozygote excess at many loci in most populations indicated that M. saniculifolia was influenced by a substantial degree of inbreeding in both regions. The degree of differentiation between populations was remarkably higher in the MJ region than in the DY region. Cluster analysis showed a trend towards separation between regions, although populations in the MJ region exhibited a slightly different trend according to the markers. We conclude that genetic drift has been affecting the populations in the MJ region for a long time, on the basis of their low genetic diversity, high differentiation, U-shaped allele-frequency distribution, and fixation of alleles towards opposing frequencies (1 or 0) among populations. In contrast, the DY region maintained relatively stable populations, although evidence of a recent bottleneck was found in one population. Along with some practical measures for genetic conservation, we present an optimal sample size for ex situ conservation to secure as many common alleles as possible.