No abstract

The dynamic properties of phospholipid (PL) membranes (phase state and phase transition) play crucial roles in biological systems. However, highly sensitive, direct analytical methods that shed light on the nature of lipids and their assemblies have not been developed to date. Here, we describe the analysis of PL-modified Au nanoparticles (Au@PL) using membrane surface-enhanced Raman spectroscopy (MSERS) and report the properties of the self-assembled PL membranes on the Au nanoparticle. The Raman intensity per PL concentration increased by 50-170 times with Au@PL, as compared to large unilamellar vesicles (LUVs) at the same PL concentration. The phase state and phase transition temperature of the PL membrane of Au@PL were investigated by analyzing the Raman peak ratio (R = I2882/I2930). The enhancement at 714 cm(-1) (EF(714)) varied with the hydrocarbon chain length of the PLs and the assembled degree of Au@PLs. In calculation, the EF(714),assembled was estimated to be 111-142 when the distance between AuNPs was 7.0-7.5 nm, which was correlated to the speculative enhancement factor, suggesting that the assembly of the Au@PLs contributed to the MSERS.

We assessed the vertical distribution of litter and its seasonal patterns in the canopy and on the forest fl oor (soil), as well as litterfall (the fl ux of litter from the canopy to the soil) in a 33-year-old plantation of Japanese cedar (Cryptomeria japonica D. Don). The masses of total litter, dead leaves, and dead branches in the canopy of C. japonica trees averaged 34.09, 19.53, and 14.56 t dry wt ha −1 , respectively, and were almost constant during the study period. The total masses of the annual litterfall were 4.17 and 5.88 t dry wt ha −1 year −1 in the two consecutive years of the study. The mass of the soil litter averaged 7.95 t dry wt ha −1 during the same period. All relationships between the mass of canopy litter and tree-size parameters (diameters at breast height and at the lowest living branch) were linear in a log-linear regression. Compared with the results for this plantation at a younger stage (16 years old), our results suggest that the total mass of dead leaves attached to each tree increases markedly with increasing age, but that the trajectory of this increase as a function of tree size may change from an exponential to a saturation curve with increasing stand age.

In a Cryptomeria japonica plantation, we examined the composition and seasonal abundance of microarthropods in communities associated with "habitat substrates" in the canopy (defined as dead leaves, dead branches, and living leaves) and compared them with those in soil communities. Habitat substrates and microarthropods were periodically collected by the branch-clipping and washing method from the canopy and by the Tullgren method from the soil. Oribatida, Collembola, and larvae of the Chironomidae, most of which are detritivorous or fungivorous, were dominant in the canopy. The dominant oribatid and collembolan families differed markedly between the canopy and the soil. Numbers of all microarthropods per unit dry weight of leaf or per unit area of branch ranged from 4.2 to 11.7 g Ϫ1 dry wt on dead leaves, 0.13-0.48 cm Ϫ2 on dead branches, and 1.3-6.4 g Ϫ1 dry wt on living leaves. In the soil, the number of individuals per unit ground area ranged from 24 000 to 220 000 m Ϫ2 . The total abundances of microarthropods on dead leaves and dead branches were almost constant throughout the year. These results suggest that the arboreal litter characteristic of C. japonica canopies is utilized consistently by large numbers of detritivorous and fungivorous microarthropods, and that the decomposition of dead foliage and branches is initiated in the canopy.

We compared the structure of spider assemblages between the upper and lower canopy layers, and between the canopy and forest door, in plantations of evergreen cedar (Cryptomeria japonica) and deciduous larch (Larix kaempferi). The estimated number of species was similar between the upper and lower canopy layers (49.0 vs 45.1) in C. japonica, but was noticeably smaller in the upper canopy layer (11.3) than in the lower layer (36.9) in L. kaempferi. Arboreal spider assemblages in the canopy differed significantly between the upper and lower layers in both C. japonica and L. kaempferi stands, based on an abundance-based measure. However, based on an incidence-based measure, they only differed significantly between layers in the L. kaempjeri stand. The spider assemblages also differed distinctly between the canopy and the forest floor in both stands. Wandering spiders and orb-web builders were dominant in the canopy, while space-web builders dominated the forest floor in the C. japonica stand. In the L. kaempferi stand, wandering spiders dominated both the canopy and the forest floor. Our results suggested that spider assemblages in conifer plantations were distinctive among strata because of differences in such factors as resource quality (i.e., living or dead foliage) and association with adjacent layers along the vertical gradient of the forests.