温帯の散孔材樹種における道管サイズの季節変化と水分条件との関係

Vessel lumen area and leaf water potential (ψleaf) at predawn and midday were measured periodically to reveal seasonal variations in the vessel sizes of diffuse-porous species and to determine the factors that cause this variation. Two deciduous species (Cercidiphyllum japonicum and Liriodendron tulipifera) and one evergreen species (Quercus glauca) were studied. In most of the samples, mean vessel lumen area (MVLA) initially increased then eventually decreased after a period, but this period varied among species. In C. japonicum, the decrease in MVLA coincided with a decrease in predawn ψleaf. In contrast, MVLA variations in most samples of L. tulipifera and Q. glauca did not show such a relationship. However, one of the L. tulipifera samples had an earlier decrease in MVLA that coincided with a lower predawn ψleaf. There was no clear relationship between the variation in vessel size and midday ψleaf, because midday ψleaf showed daily variation depending on vapor pressure deficit, which had less seasonality. Thus, we concluded that there are species-specific annual patterns in vessel size variation that are likely determined by internal factors. Low water availability is one of the external factors inducing the formation of narrower vessels.散孔材における道管サイズの季節変化, およびその変化を引き起こす要因を明らかにするため, 道管形成の観察と夜明け前と日中の葉の水ポテンシャル (ψleaf)の測定を定期的に行った. 試料には落葉樹のカツラとユリノキ, 常緑樹のアラカシを用いた. 全ての樹種で道管サイズは一年の成長の始めに増加し, ある時期から減少していた. 減少が始まる時期は樹種によって異なっており, カツラでは夜明け前のψleaf の低下と対応が見られた. 一方でユリノキとアラカシでは, 道管サイズと夜明け前のψleaf の対応は見られなかった. ただし夜明け前のψleaf が他よりも低下していた個体では道管サイズの減少が早く始まっていたため, 乾燥ストレスの影響が示唆された. 日中のψleaf は日変動が大きく, 道管サイズとの明確な関連性は見られなかった. したがって, 年輪内の道管サイズの変化は主に内的要因によって決まっており, 乾燥ストレスは外部要因として道管サイズを減少させると考えられた

Radial and vertical distributions of radiocesium in tree stems of Pinus densiflora and Quercus serrata 1.5 y after the Fukushima nuclear disaster.

The radial and vertical distributions of radiocesium in tree stems were investigated to understand radiocesium transfer to trees at an early stage of massive contamination from the Fukushima nuclear disaster. A conifer species (Japanese red pine) and a broad-leaved species (Japanese konara oak) were selected to determine whether the radiocesium contamination pattern differs between species. Stem disks were collected at several heights and separated into outer bark, inner bark, and wood. The radiocesium concentration was the highest in the outer bark, followed by that in the inner bark and wood. The vertical distribution of the radiocesium concentration at each stem part differed between the species. The difference between species in radiocesium concentration of the outer bark could be explained by presence or absence of leaves at the time of the disaster. However, the reasons for the differences between species in the radiocesium concentration of the inner bark and wood are unclear. The radial distribution in the wood of the studied species showed a common pattern across stem disk heights and species. However, the radiocesium concentration ratio between sapwood and inner bark was significantly different between species. Although the radial contamination pattern in the wood was similar in the studied species during the early stage of contamination, the radiocesium transport pathway and allocation would be different between the species, and the contamination pattern will likely be different between the species at later stages. Continued investigations are important for understanding the radiocesium cycle and the accumulation of radiocesium in the tree stems of each species

Estimation of tree age in the humid tropics by vessel measurement: a preliminary study

We estimated the age of plantation-grown trees lacking distinct and consistent annual rings to examine whether an anatomical method for determining the vessel traits of wood is effective in the tropical rain forest climate. Stem disks from 1 Dipterocarpaceae and 2 Meliaceae species for which the planting year was known were collected, and radial strips were sawn out from 2 different radii on each disk. We measured mean vessel lumen area (MVLA) and vessel frequency (VF) and found that radial changes in the 2 variables showed cyclic variation in all samples. The cycle number of both MVLA and VF mostly matched the tree age when they were analyzed with proper radial resolution. The number and shape of the cyclic variations were different between the 2 radii; this inconsistency could partly be ascribed to asynchronous cambium activity. The result implies that (1) the selection of sample species is important and (2) more than 1 radius should be analyzed to increase the accuracy of estimation. Thus, we concluded that vessel traits are important growth-ring indicators in the humid tropics, but a single application of this method of ring analysis may not be sufficiently accurate in age estimation. Further research on the factors affecting vessel formation will make the method more effective

Recovery of above-ground tree biomass after moderate selective logging in a central Amazonian forest

We examined the recovery and dynamics of living tree above-ground biomass (AGB) after selective logging in an Amazonian terra firme forest managed by a private company. The forest consisted of 24 blocks (including one set aside for conservation) selectively logged in different years on a managed schedule. Trees ≥10 cm in diameter at breast height (dbh) were surveyed in 2006 in 192 0.25-ha plots, in 2010 in 119 plots, and in 2012-2013 in 54 plots. A logistic growth model factoring in logging dynamics and mean AGB of a block in these years was established. Referencing the mean AGB of the unlogged forest, the model indicated that the logged forest would take on average 14 years to regain its preharvest AGB after selective logging at 1.9 trees ha-1 (dbh > 50 cm). In 2010 and 2012-2013, the AGB increased significantly for small and large trees (10-20 cm and >60 cm dbh, respectively) in the logged forest. In contrast, it decreased significantly for medium-sized trees (30-50 cm dbh) in the unlogged forest. Comparisons with the previous studies mainly conducted in the other regions of Amazon suggested that the estimated AGB recovery period with moderate logging intensity was almost appropriate and likely acceptable to forest managers. © SISEF

Soil fertility and drought interact to determine large variations in wood production for a hyperdominant Amazonian tree species

Introduction: The productivity of the Amazon Rainforest is related to climate and soil fertility. However, the degrees to which these interactions influence multiannual to decadal variations in tree diameter growth are still poorly explored. Methods: To fill this gap, we used radiocarbon measurements to evaluate the variation in tree growth rates over the past decades in an important hyperdominant species, Eschweilera coriacea (Lecythidaceae), from six sites in the Brazilian Amazon that span a range of soil properties and climate. Results: Using linear mixed-effects models, we show that temporal variations in mean annual diameter increment evaluated over a specific time period reflect interactions between soil fertility and the drought index (SPEI-Standardized Precipitation and Evapotranspiration Index). Discussion: Our results indicate that the growth response of trees to drought is strongly dependent on soil conditions, a facet of forest productivity that is still underexplored, and which has great potential for improving predictions of future tropical tree growth in the face of projected climate change

熱帯樹種の年輪の検出

京都大学0048新制・課程博士博士(農学)甲第16923号農博第1939号新制||農||1001(附属図書館)学位論文||H24||N4684(農学部図書室)29598京都大学大学院農学研究科森林科学専攻(主査)教授 大澤 晃, 教授 太田 誠一, 教授 髙部 圭司学位規則第4条第1項該当Doctor of Agricultural ScienceKyoto UniversityDA

Tracing radioactive cesium in stem wood of three Japanese conifer species 3 years after the Fukushima Dai-ichi Nuclear Power Plant accident

Abstract To understand the dynamics of accident-derived radioactive cesium (137Cs) in stem wood that had a substantial amount of heartwood at the time of the Fukushima Dai-ichi Nuclear Power Plant accident, the radial and vertical distributions of 137Cs activity concentration in stem wood of Japanese cedar (Cryptomeria japonica), cypress (Chamaecyparis obtusa), and larch (Larix kaempferi) were investigated. In addition, the natural distribution of stable cesium (133Cs), rubidium (85Rb), and potassium (39K) concentrations was analyzed to determine the characteristics of 137Cs distribution. Wood disks were collected from the tree stems of six cedars, three cypresses, and two larches at multiple heights in 2014, and the concentrations were measured every 2 cm in the radial direction. 137Cs distribution in stem wood differed among tree species, sampling site, and vertical position of the stem within a tree. Statistical analyses suggested that the radial distribution of 137Cs within the heartwood can be explained by the heartwood moisture content and the distance from the treetop, regardless of species, while the distribution between sapwood and heartwood was dependent on the heartwood cross-sectional area and was additionally different between larch and other species. Similarly, the heartwood/sapwood concentration ratios of stable alkali metals differed between larch and the other species. In the larch, the ratio was ca. 0.5 for all elements, but the ratio was over 1.0 and differed among elements in the other species. Consequently, the species-specific difference in the distribution of 137Cs between sapwood and heartwood was considered to be due to different activity levels of radial transport toward the heartwood. The radial variation pattern of the 137Cs/133Cs concentration ratio showed that less 137Cs was transferred to the inner heartwood compared with the 133Cs distribution pattern in many trees; however, there was also a tree in which 137Cs was excessively transferred to the inner heartwood compared with the 133Cs distribution pattern. Such patterns may result from a combination of significant foliar uptake of 137Cs and poor root uptake after the accident, in addition to the high moisture content of the heartwood

Vessel feature changes as a tool for detecting annual rings in tropical trees

Radial variations in vessel features (vessel lumen area and frequency) of four tropical tree species grown in tropical savanna, monsoon, and rainforest climates were investigated to detect indistinct annual rings. Leaf and soil water potentials were measured periodically to show annual variations in water availability and their relationship to radial variations in vessel features. In addition, the accuracy of annual-ring detection was estimated using trees of known age. Radial variations in vessel features showed annual cyclicity in all three sites. The vessel feature that showed clear annual cyclicity was different among the species and sites. Furthermore, the variation pattern of vessel features in the rainforest site tended to be different between two radii within individual trees, implying low synchronicity of wood formation in the wet area. Compared with leaf and soil water potentials, vessel features varied independent of water availability in all species in the rainforest site and most species in the savanna and monsoon sites. The direct effect of low water availability on vessel features was considered only in one species in the savanna and monsoon sites. Nevertheless, the deviation of vessel feature cycles from tree age was similar and reasonably small (mostly within ±10 %) among all sites. These results indicated a circannual rhythm in vessel formation. Thus, vessel feature changes seemed to aid in detecting annual rings in trees throughout wide tropical areas; however, asynchronous wood formation must be considered in dendrochronology, especially in humid tropics

Seasonal variations in the stable oxygen isotope ratio of wood cellulose reveal annual rings of trees in a Central Amazon terra firme forest.

In Amazonian non-flooded forests with a moderate dry season, many trees do not form anatomically definite annual rings. Alternative indicators of annual rings, such as the oxygen (δ(18)Owc) and carbon stable isotope ratios of wood cellulose (δ(13)Cwc), have been proposed; however, their applicability in Amazonian forests remains unclear. We examined seasonal variations in the δ(18)Owc and δ(13)Cwc of three common species (Eschweilera coriacea, Iryanthera coriacea, and Protium hebetatum) in Manaus, Brazil (Central Amazon). E. coriacea was also sampled in two other regions to determine the synchronicity of the isotopic signals among different regions. The annual cyclicity of δ(18)Owc variation was cross-checked by (14)C dating. The δ(18)Owc showed distinct seasonal variations that matched the amplitude observed in the δ(18)O of precipitation, whereas seasonal δ(13)Cwc variations were less distinct in most cases. The δ(18)Owc variation patterns were similar within and between some individual trees in Manaus. However, the δ(18)Owc patterns of E. coriacea differed by region. The ages of some samples estimated from the δ(18)Owc cycles were offset from the ages estimated by (14)C dating. In the case of E. coriacea, this phenomenon suggested that missing or wedging rings may occur frequently even in well-grown individuals. Successful cross-dating may be facilitated by establishing δ(18)Owc master chronologies at both seasonal and inter-annual scales for tree species with distinct annual rings in each region

Environmental transfer parameters for radionuclides released from the accident at the Fukushima Daiichi Nuclear Power Plant. Chapter 5 Forest ecosystems

Approximately 70% of the territory affected by the Fukushima Daiichi accident is covered by forest (Fig. 5.1) [5.1]. Forests in Fukushima prefecture consist of about 0.34 million ha of forest plantations and 0.58 million ha of natural/semi natural forest. In this section, radiocaesium interception by tree canopy, transfer to tree and forest products (sansai, mushrooms and game animals), and mobility in tree and soil are described