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Estimation of the current successional status of long-lived coniferous forests is difficult especially after several hundred years of human disturbance. However, inCryptomeria japonicaforest on Yakushima Island, the stumps generated by logging activities from the seventeenth to nineteenth centuries remain almost intact without intense rotting. From an inventory of these stumps and long-term monitoring of current stands for more than 25 years, we estimated the forest condition before logging and evaluated the current status of secondary succession. The size structure ofCr. japonicastumps suggested the stumps were composed of two different generations: the stumps of trees present before initiation of logging; and those of trees that regenerated after initiation of logging. In the current forest, the stem number of canopy species is decreasing and that of understory broad-leaved species is increasing. RegeneratingCr. japonicaindividuals are rare. Before the logging, the forest contained a larger number of largerCr. japonicatrees than the current forest. The results of monitoring the current forest suggested that all coniferous species, includingCr. japonica, were still undergoing self-thinning. The currentCr. japonicaforest is in an intermediate stage of secondary succession, but the processes of succession are markedly different between the study plots, depending on their location or previous logging intensity. [ABSTRACT FROM PUBLISHER]

The daily total photosynthetically active radiation (400-700 nm, PAR) and near-infrared radiation (700-1000 nm, NIR) were measured in the understory beneath the canopy (PARt and NIRt) and above the canopy (PARi and NIRi) of a Japanese cool-temperate deciduous broad-leaved forest during the snow-free period (May to November). The integration of spectral radiation for NIR and that for PAR, and the daily integrations of instantaneous NIR and PAR, reduced the noises from the optical difference in spectrum and from canopy structure heterogeneity, sky condition and solar elevation. PARi/PARt was linearly related to NIRt/PARt ( R² = 0.96). The effect of cloudiness was negligible, because the fluctuation of NIRi/PARi was quite small regardless of season and weather conditions compared with the range of NIRt/PARt in the forest. The ratio of NIRt/PARt beneath the canopy was log-linearly related to the in situ leaf area index (LAI) with a wide range from 0 to 5.25 ( R² = 0.97). We conclude that seasonal changes in fAPAR (= 1 − PARt/PARi) and LAI of a canopy can be estimated with high accuracy by transmitted NIRt and PARt beneath the canopy. [ABSTRACT FROM AUTHOR]

Four types of indices of canopy characteristics were compared to estimate understory light conditions using crown projection maps and topographic data. Crown area (CA) was formulated from the crowns in a focal sub-block (20 m×20 m). Canopy shade index (CSI) was formulated from the crowns in a focal sub-block and the surrounding sub-blocks with topographic effect. Site shade index (SSI) incorporated the shade of the slopes into CSI and represented the total physical closure of the site. Site light index (SLI) incorporated the azimuth of the site into SSI and evaluated the light condition of the understory. We tested the methods using the data on steep old-growth Cryptomeria japonica forests on Yakushima Island and the three-dimensional canopy structures of the forests were digitized on a geographic information system. The results were validated by the basic indices obtained by hemispherical photographs: canopy openness (CO) and gap light index (GLI). The three-dimensional structure of the surrounding canopies and topography had significant effects on the understory light conditions. CA had no significant correlation with CO, whereas CSI and SSI had significant negative correlations with CO. Although SLI had the highest negative correlation with GLI ( R 2=0.69), CSI had practical utility in the estimation of GLI ( R 2= 0.65). Our method is applicable to past crown projection maps that have been recorded at many forest research sites, thus making it possible to reconstruct past understory light conditions and to compare them with present conditions. [ABSTRACT FROM AUTHOR]

Dwarf bamboo,Pleioblastus chino, grows extensively in abandoned coppice woodlands on the Kanto Plain in central Japan and suppresses other understory plants. In order to clarify the factors determining the growth ofP. chino, we considered the effect of light conditions under a coppice canopy and examined its relationship with slope aspect, slope angle, and basal area of the trees. The relative photon flux density under the canopy was highly correlated with canopy coverage (R2 = 0.97). The light conditions under the canopy were almost the same at all sites in the summer leafy season regardless of the stand type, while they were remarkably different among the sites and depended on the basal area of evergreen trees in the winter leafless season. The biomass ofP. chinoon the forest floor was described by the equation:y= 3.18x1 - 0.05x2 + 3.11 (R2 = 0.77,P<0.01), whereyis the log-transformed value ofP. chinobiomass (g?dry?mass?m-2),x1 is cos?? at solar noon at the winter solstice, andx2 is the canopy coverage during the winter leafless season. ? is the angle between the sun’s rays and the normal to the surface and changes with slope aspect and angle. We concluded that light conditions under the canopy in the leafless season had a great effect onP. chinobiomass, and that the basal area of evergreen trees and slope characteristics can provide useful guidelines in the control and management ofP. chino. [ABSTRACT FROM AUTHOR]

In order to consider the effects of light quality on the growth of understory plants, both the direct and diffuse components of solar radiation must be evaluated. However, the basis for choosing the threshold between the two components of radiation has not been systematically determined. We evaluated the basis and methods for separating direct and diffuse radiation under field conditions. Daily courses of direct and diffuse photosynthetic photon flux densities (PPFDs) over and under canopies were measured with quantum sensors and were predicted from hemispherical photographs. We proposed a new variable, called the diffuse coefficient of canopy (dc), to compensate for the increase in the diffuse radiation component as the sunlight passes through the overstory canopy. dc was highly correlated with canopy coverage (cc) (dc = 0.01cc - 0.3, r2 = 0.95). For woodland sites, PPFD can be predicted from hemispherical photographs according to the following equations: Wdir = Sout(τ - dc)M sinα and Wdif = Sout (0.271 - 0.294(τ - dc)M) sinα, where Wdir and Wdif are the direct and diffuse radiation components in woodland sites, Sout is the extraterrestrial PPFD normal to the solar beam, τ is the atmospheric transmittance, M is the optical airmass number and α is the solar elevation. The daily courses of PPFD and sunflecks under canopies can be estimated from hemispherical photographs when the effects of dc are considered. [ABSTRACT FROM AUTHOR]

A correction to the article "Canopy Rainfall Interception and Fog Capture by Pinus pumila Regal at Mt. Tateyama in the Northern Japan Alps, Japan" that was published in the previous issue is presented.