Landslide-facilitated species diversity in a beech-dominant forest

To evaluate the extent to which landslides affect community dynamics and consequent species diversity in a beech-dominated forest, differences in the composition and size structure of tree species were compared between landslide and adjacent stable (control) stands. Demography and changes in size were compared between the two stands over a 5-year period about 60 years after a landslide. In the control stand, replacement occurred even amongst late-successional species, with beech (Fagus crenata)—the most dominant species—increasing in relative abundance. In the landslide stand, very few large individuals of late-successional species occurred, whereas large individuals of early-successional species occurred only in the landslide stand. The traits indicate that the landslide strongly facilitated species diversity, not only by reducing the dominance of late-successional species, but also by promoting recruitment of early-successional species. However, new recruitment of early-successional species was inhibited in the landslide stand, although we observed succeeding regeneration and subsequent population growth of late-successional species there. As a result, the relative dominance of late-successional species increased with succession after the landslide, thus decreasing future species diversity. In beech-dominant forest landscapes in Japan that include communities with different developmental stages, the mosaic of serial stages may facilitate species diversity after a landslide.     

Molecular design of N-linked tetravalent glycosides bearing N-acetylglucosamine,N,N′-diacetylchitobiose and N-acetyllactosamine: Analysis of cross-linking activities with WGA and ECA lectins

Two types of nonspacer- and spacer-N-linked tetravalent glycosides bearing N-acetylglucosamine (GlcNAc), N,N′-diacetylchitobiose [(GlcNAc)₂] and N-acetyllactosamine (LacNAc) were designed and prepared as glycomimetics. The interactions of wheat germ (Triticum vulgaris) agglutinin (WGA) and coral tree (Erythrina cristagalli) agglutinin (ECA) with a series of tetravalent glycosides and related compounds were studied using a hemagglutination inhibition assay, a precipitation assay, double-diffusion test, and an optical biosensor based on surface plasmon resonance (SPR). The tetravalent glycosides were found to be capable of binding and precipitating the lectins as tetravalent ligands. Strong interactions with WGA, due to a combination of multivalency effects and spacer effects, were observed for tetravalent glycosides bearing flexible tandem GlcNAc. The chelate effect leads to large rate enhancement for the tetravalent system with favorable orientation of ligands. Our simple strategy produced multivalent glycosides with strong cross-linking activity for lectin as a specific coagulant.     

Leaf diseases drive the Janzen–Connell mechanism regardless of light conditions: a 3-year field study

In forests, negative density/distance-dependent seedling mortality (NDD) caused by natural enemies plays a key role in maintaining species diversity [Janzen–Connell (J–C) model]. However, the relative importance of natural enemies in mediating NDD under heterogeneous light conditions has remained unclear. We examined the relative importance of pathogens (i.e., soil pathogens, leaf diseases) on seedling performance in forest understories (FUs) and gaps (gaps) during a 3-year period (results of first year of our study have been previously reported). For the hardwood, Prunus grayana, we investigated seedling mortality, morbidity agents, growth, and root infection by arbuscular mycorrhizal fungi (AMF) beneath conspecific and heterospecific adults in FUs and gaps. Seedling mortality was higher beneath conspecific than heterospecific adults throughout 3 years at both sites, mainly due to continuous leaf disease (i.e., angular leaf spot), whereas damping-off diseases caused mortality only in the first year. Beneath each adult, seedling mortality was higher in FUs than in gaps until second year, but it did not differ between two habitat types in the third year, because leaf diseases caused severe damage even in gaps. Seedling mass was significantly lower beneath conspecific adults. AMF infection of seedlings was also lower beneath conspecific adults, while it was higher in gaps than in FUs beneath both adults. This study demonstrates that the J–C model in a hardwood tree, P. grayana is mainly driven by high NDD seedling mortality caused by airborne leaf diseases, which continuously attack seedlings in a NDD manner regardless of environmental light conditions.     

Mycorrhizae ofMonotropastrum globosum growing in aFagus crenata forest

The achlorophyllousMonotropastrum globosum was found growing in aFagus crenata forest. Samples ofM. globosum and their interpenetrating root systems ofF. crenata were collected to investigate the mycorrhizal association.Monotropastrum globosum mycorrhizae showed thick sheaths, invasion of the epidermal cells by fungal pegs, and Hartig nets, which reached only the first layer of cortical cells. TheF. crenata mycorrhizae also showed thick sheaths, but Hartig nets penetrated deep into the cortex and intracellular hypha were seen in the outer cortical cells. The similarities observerd in the mantle inner plan view and emanating hypha suggest that both mycorrhizae are formed by the same fungus.     

Inter-tree variation and yearly fluctuation in the susceptibility of Sakhalin spruce Picea glehnii, to shoot-boring sawfly Pleroneura piceae

This study evaluated the effect of inter-tree variation in the bud phenology of Picea glehnii on susceptibility to the shoot-boring sawfly. Pleroneura piceae , and found that individual susceptibility fluctuates from year to year. The mechanism for the fluctuation between 1994 and 1997 is discussed.
Inter-tree difference in the time of bud swelling is probably genetically based, since most of the trees that began to swell early in 1995 also swelled early in 1997, and those that began to swell late also did so in both years. Damage severity of each tree was evaluated by damage ratio: proportion of the number of damaged current shoots on the previous year's leader shoot. The rank of the bud swelling phenology of a tree was positively correlated to the rank of the damage ratio. This means that genetically based differences in phenology could explain why some trees are subjected to higher levels of herbivory than others.
There was year-to-year variation in the damage severity for each tree. Nevertheless, no significant differences were found in the rank of the damage ratio between years. However the standard deviation of the damage ratios of each tree was highest for trees of intermediate rank. The skew of the frequency distribution of damage ratio was negatively correlated to the cumulated daily mean temperature in spring, which means that the spruce is more susceptible to the sawfly in warm springs than in cool springs.
The mean growth rate of the lightly damaged trees increased constantly, while that of the heavily damaged trees seemed to reach a limit and then became lower than that of the lightly damaged trees.     

Modelling the Masting Behaviour of Betula platyphylla var. japonica using the Resource Budget Model

A masting model of Betula platyphylla var. japonica, a majorwind-pollinated tree in Hokkaido, northern Japan, was constructedfrom the perspective of the resource budget model. An 11-yeardata series of pollen dispersal by birch showed marked annualfluctuations in flowering. Although flowering fluctuated widelyamong years, a reciprocal relationship was observed betweentwo consecutive years; very little flowering occurred aftera mast year. This suggests that there is a negative relationshipbetween current fruiting and flower bud induction. There wasa significant positive relationship in flowering between regions,which suggests that weather conditions regulate flowering inbirch. A model that included weather variables and resourceallocation systems among years explained 94·5% of theobserved annual fluctuations in flowering. In the model, warmspring conditions from bud burst to flower bud development andlittle flowering in the previous year (t-1) resulted in increasedflowering in the current year (t), whereas abundant floweringin year t-2 resulted in a decrease in flowering in the currentyear (t). The latter indicates that flowering in year t-2 affectsresource storage after overwintering; the balance is carriedforward to year t-1 and affects the initiation of flower primordiabefore bud burst. In the model, fluctuating weather conditionsin the previous spring strongly affected the masting behaviourof birch. Copyright 2001 Annals of Botany Company Betula platyphylla var. japonica, flowering, masting, modelling, pollen dispersal, resource allocation, resource budget model, weather conditions     

Effects of ACTH, dexamethasone, adrenalectomy and stress on cAMP content of adenohypophysis and adrenals in rats.

The effects of adrenalectomy, ether-laparotomy stress and in vivo administration of either ACTH or dexamethasone on the cAMP levels in the anterior pituitary and the adrenal glands were investigated in male rats. After adrenalectomy or ether-laparotomy stress, an increase of the pituitary cAMP levels was observed. A prior administration of dexamethasone failed to inhibit the increase of the pituitary cAMP levels. Acute administration of dexamethasone increased the cAMP levels in the pituitary. Chronic administration of dexamethasone decreased the cAMP levels in the pituitary, but ACTH did not. These data suggest that cAMP might be involved in the mediation of the hypothalamo-pituitary-adrenal axis.     

Floral sex allocation at individual and branch levels in Betula platyphylla var. japonica (Betulaceae), a tall, wind-pollinated monoecious tree species

Floral sex allocation at the individual and first-order branch levels and the relation between these levels were examined in Betula platyphylla var. japonica, a wind-pollinated monoecious tree. Floral sex allocation at the individual level varied with resource availability in a pattern similar to that predicted by the Masaka and Takada model (Journal of Theoretical Biology 240: 114-125). Thus, individual trees with few reproductive resources produced only female or male inflorescences, whereas individuals with many resources rarely had a high male ratio (i.e., number of male inflorescences/total number of inflorescences). Furthermore, the number of male inflorescences tended to reach an upper limit, whereas the number of female inflorescences increased monotonically with increasing reproductive investment. The patterns of floral sex allocation at the first-order branch level were analogous to those at the individual level. Thus, each first-order branch of B. platyphylla var. japonica behaves like an individual, and the floral sex allocation of a given branch does not necessarily represent the individual tree. The effect of the individual-level floral sex ratio on branch-level floral sex allocation indicates that branch behavior is controlled by the individual.