Koh Yasue

The effects of tracheid dimensions on variations in maximum density of Picea glehnii and relationships to climatic factors

Abstract An investigation was made of the effects of tracheid dimensions on variations in the maximum density of Picea glehnii Mast., which were associated with climatic changes. Radial cell diameter and the thickness of the tangential cell walls of the last-formed cells in 90 annual rings of nine trees with different annual ring widths were analyzed by image analysis. Correlations between maximum density and tracheid dimensions indicated that changes in maximum density were due mainly to changes in cell wall thickness of the last-formed cells in annual rings and were not due to changes in radial cell diameter. The effects of climatic factors on tracheid dimensions were examined by application of dendroclimatological techniques. A chronology of cell wall thickness that represented common signals among trees was established. Simple correlation and response function analyses of the chronology revealed that cell wall thickness was influenced positively by summer temperature and negatively by precipitation in August, and these responses were similar to those of maximum density. The study demonstrated that variations in maximum density were due to variations in the cell wall thickness of the last-formed cells, which varied depending on the weather in summer.

Effects of climate on the radial growth of tree species in the upper and lower distribution limits of an altitudinal ecotone on Mount Norikura, central Japan

Tree-ring width chronologies were developed for Abies veitchii, Betula ermanii and Betula platyphylla var. japonica in their altitudinal ecotone (approximately 1600 m a.s.l.) on Mount Norikura, central Japan, to determine what climatic conditions affect the growth of tree species in the upper and lower distribution limits of an altitudinal ecotone. This altitude was the lower distribution limit for A. veitchii and B. ermanii in the subalpine zone, and was the upper distribution limit for B. platyphylla var. japonica in the montane zone on Mount Norikura. Tree-ring widths of the two Betula species and A. veitchii were positively correlated with the August precipitation of the current and previous years, respectively. Precipitation in August (the hottest month) was reduced compared with other months during summer. Tree-ring width of B. platyphylla var. japonica showed no correlation with temperatures in any month in its upper distribution limit. In contrast, tree-ring widths of B. ermanii and A. veitchii were negatively correlated with the August temperatures of the current and previous years, respectively, at the lower distribution limit of these species. Therefore, the two Betula species and A. veitchii responded to climatic conditions of the current and previous years, respectively. The present study also suggests that a water deficit in August reduces growth of these three species in this altitudinal ecotone, irrespective of the upper or lower distribution limits, and that a high August temperature is more detrimental to the growth of A. veitchii and B. ermanii in their lower distribution limits. Thus, the three species with different altitudinal distributions examined in the present study responded differently to climatic conditions in this altitudinal ecotone on Mount Norikura.

The effects of localized heating and disbudding on cambial reactivation and formation of earlywood vessels in seedlings of the deciduous ring-porous hardwood, Quercus serrata.

BACKGROUND AND AIMS The networks of vessel elements play a vital role in the transport of water from roots to leaves, and the continuous formation of earlywood vessels is crucial for the growth of ring-porous hardwoods. The differentiation of earlywood vessels is controlled by external and internal factors. The present study was designed to identify the limiting factors in the induction of cambial reactivation and the differentiation of earlywood vessels, using localized heating and disbudding of dormant stems of seedlings of a deciduous ring-porous hardwood, Quercus serrata. METHODS Localized heating was achieved by wrapping an electric heating ribbon around stems. Disbudding involved removal of all buds. Three treatments were initiated on 1 February 2012, namely heating, disbudding and a combination of heating and disbudding, with untreated dormant stems as controls. Cambial reactivation and differentiation of vessel elements were monitored by light and polarized-light microscopy, and the growth of buds was followed. KEY RESULTS Cambial reactivation and differentiation of vessel elements occurred sooner in heated seedlings than in non-heated seedlings before bud break. The combination of heating and disbudding of seedlings also resulted in earlier cambial reactivation and differentiation of first vessel elements than in non-heated seedlings. A few narrow vessel elements were formed during heating after disbudding, while many large earlywood vessel elements were formed in heated seedlings with buds. CONCLUSIONS The results suggested that, in seedlings of the deciduous ring-porous hardwood Quercus serrata, elevated temperature was a direct trigger for cambial reactivation and differentiation of first vessel elements. Bud growth was not essential for cambial reactivation and differentiation of first vessel elements, but might be important for the continuous formation of wide vessel elements.

Continental-Scale Temperature Variability during the Past Two Millennia: Supplementary Information

Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between ad 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming reversed the long-term cooling; during the period ad 1971–2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years.

Radial variations in the anatomical characteristics and density of the wood of Acacia mangium of five different provenances in Indonesia

The anatomical characteristics and density of wood were examined in 23-year-old Acacia mangium trees that had been planted in Yogyakarta, Indonesia. The seeds had been collected from trees of five different provenances. The distance from the pith of the boundary between juvenile and mature wood was also examined to clarify the maturity of the wood. Lengths of wood fibers near the pith and the distance from the pith of the boundary between juvenile and mature wood differed significantly among provenances. By contrast, other anatomical characteristics of the wood such as fiber wall area, fiber wall thickness, fiber diameter, vessel lumen area, vessel diameter, vessel frequency and wood density did not differ significantly among provenances. Wood density was strongly correlated with the area of fiber walls. Our observations suggest that Sidei and Daintree might be more appropriate provenances among those examined for the Acacia mangium tree-breeding programs in Indonesia that are aimed at improving wood quality, because these provenances are associated with longer initial wood fibers and narrower juvenile areas than the other provenances studied.

Responses to climate by tree-ring widths and maximum latewood densities of two Abies species at upper and lower altitudinal distribution limits in central Japan

This study examined the effects of climate on tree-ring widths and maximum latewood densities of Abiesveitchii and Abies mariesii at the upper and lower distribution limits in central Japan. A. veitchii and A. mariesii dominated at the lower and upper parts of the subalpine zone, respectively. Residual chronologies of tree-ring width and maximum latewood density were developed for the two Abies species at the upper and lower distribution limits, and were compared with monthly mean temperatures and monthly sums of precipitation. Tree-ring widths of the two Abies species at the upper and lower distribution limits positively correlated with temperatures during the beginning of the dormant season and during the growing season of the current year, except for A. veitchii at the lower distribution limit, which showed no positive correlation with temperature. Maximum latewood densities of the two Abies species at the upper and lower distribution limits positively and negatively correlated with temperatures and precipitation, respectively, during the growing season of the current year. Therefore, tree-ring widths and maximum latewood densities of the two Abies species were sensitive to low temperature, except for the tree-ring width of A. veitchii at the lower distribution limit with the warmest thermal conditions along the altitude. Global warming is suggested to affect maximum latewood densities and tree-ring widths of the two Abies species along the altitude.

On the radial-growth variations of Japanese beech (Fagus crenata) on the northernmost part of Honshu Island, Japan

We developed ring-width chronologies for living trees of Japanese beech at two forest sites on the northern-most part of Honshu Island, Japan. A statistical threshold (running expressed population signal) yielded these site chronologies spanning 1853–1994 (142 years) and 1867–1994 (128 years). We examined two factors, climate and masting, that could affect the variations of radial growth. The response function analysis revealed that the ring width correlated positively with July and August temperatures of the previous growth year. The optimal radial growth of Japanese beech may largely depend on a warm previous summer with above-average temperatures. The years of good masting coincided mostly with those showing abrupt growth depression, although only the short-term records of masting were available.

Responses of ring widths and maximum densities of Larix gmelinii to climate on contrasting north- and south-facing slopes in central Siberia

An analysis was performed of the climatic responses of the radial growth of Larix gmelinii (Rupr.) Rupr. at two sites—both of which included contrasting north- and south-facing slopes—in Tura, central Siberia, with the development of ring width and maximum-density chronologies for each slope. Both residual and standard chronologies of ring widths were positively correlated with temperature from late May until mid June on all four slopes. By contrast, standard chronologies of ring widths were negatively correlated with precipitation during the winter (from October to April) and in May on the north-facing slope at site 1 and on the south-facing slope at site 2 respectively. The negative correlations with precipitation during the winter and in May on some of the slopes suggested that delayed snowmelt in early spring might inhibit the radial growth of L. gmelinii, and the effects of snow are likely to vary with topography. Both residual and standard chronologies of maximum densities were positively correlated with temperature in early July on all four slopes. Maximum densities were also positively correlated with precipitation during summer of the previous year on all the slopes. These suggest that no major differences exist in terms of responses of maximum density to climatic factors between the north- and south-facing slopes.

Relationship between formation of earlywood vessels and leaf phenology in two ring-porous hardwoods, Quercus serrata and Robinia pseudoacacia, in early spring

In deciduous ring-porous hardwoods, three-dimensional networks of the current year’s earlywood vessels play an important role in the movement of water. In the present study, we analyzed the formation of earlywood vessels along the main stem and leaf phenology in two deciduous ring-porous hardwoods, Quercus serrata and Robinia pseudoacacia. We introduced a dye in an effort to monitor the timing of initial water conduction through the network of the current year’s earlywood vessels. The formation of earlywood vessels began before bud break. At bud break, perforation of the first earlywood vessels was evident at the top of the stem but not at other positions within the stem. Perforations were observed along the entire stem when small leaves became visible and then leaves continued to develop. These results suggest that conduction of water via the network of the first earlywood vessels of the current year might not contribute to the initial growth of buds but might play an important role in the development of the current year’s leaves and shoots.

Climatic responses of tree-ring widths of Larix gmelinii on contrasting north-facing and south-facing slopes in central Siberia

An analysis was performed on the climatic responses of the radial growth of Larix gmelinii (Rupr.) Rupr. on contrasting north-facing and south-facing slopes in Tura, central Siberia. We developed chronologies of tree-ring width for four plots, designated as north-upper, northlower, south-upper, and south-lower. Both residual and standard chronologies of tree-ring widths exhibited a significant positive correlation with temperature from the end of May until early June in all four plots. The chronologies of ring width did not reveal any major difference in the response to temperature among the four plots. The standard chronologies of ring widths on the north-facing slope were negatively correlated with precipitation during the winter (October–April) and in early and mid-May, whereas the residual chronologies did not reveal clear relationships with precipitation during the winter and May. The significant correlation between ring width and temperature from the end of May until early June indicates that temperatures in springtime play a significant role in the radial growth of L. gmelinii. The negative correlations between standard chronologies of tree-ring width and precipitation in the winter and in May on the north-facing slope indicate that lowfrequency fluctuations in snowfall have negative effects on the radial growth. However, these effects vary and depend on the microscale topography.