Effect of elevated [CO2] on stem wood properties of mature Norway spruce grown at different soil nutrient availability

The objective of the present study was to investigate the interactive effects of elevated [CO₂] and soil nutrient availability on secondary xylem structure and chemical composition of 41‐year‐old Norway spruce (Picea abies (L.) Karst.) trees. The nonfertilized and irrigated‐fertilized trees were, for 3 years, continuously exposed to elevated [CO₂] in whole‐tree chambers. Elevated [CO₂] decreased concentrations of soluble sugars, acid‐soluble lignin and nitrogen in stem wood, but the effects were not consistent between sampling height and/or fertilization. The effect of 2*ambient [CO₂] on wood structure depended on the exposure year and/or fertilization. Radial lumen diameter decreased and annual ring width increased in the second year of exposure (1999) in elevated [CO₂]. In the latter, the CO₂ effect was significant only in the nonfertilized trees. Stem wood chemistry and structure were significantly affected by fertilization. Fertilization increased the concentrations of nitrogen and gravimetric lignin, annual ring width, and radial lumen diameter. Fertilization decreased C/N ratio, mean ring density, earlywood density, latewood density, cell wall thickness, cell wall index, and latewood percentage. We conclude that elevated [CO₂] had only minor effects on wood properties while fertilization had more marked effects and thus may affect ecosystem processes and suitability of wood for different end‐use purposes.     

Morphological responses of Leymus chinensis (Poaceae) to the large-scale climatic gradient along the North-east China Transect (NECT)

A field experiment was conducted to examine the morphological variations of Leymus chinensis along the climatic gradient of the North‐east China Transect (NECT), from 115° to 125° E, in the vicinity of 43.5° N, in north‐eastern China. Ten sites selected for plant sampling along the gradient have approximately uniform theoretical radiation, but differ in precipitation and geographical elevation. The results of analyses showed that vegetative and reproductive shoot heights, flag leaf lengths and widths and seed numbers per inflorescence increased from the west to the east with precipitation, but decreased with aridity. Leaf lengths and widths for most leaf types from 115° to 124° E exhibited little variations. Significant correlations of plant heights, flag leaf lengths and widths and seed numbers per inflorescence with large‐scale climatic variables (e.g. annual precipitation, aridity) and geographical variation (longitude) found in this study indicated that climatic factors have significant effects on some morphological traits of L. chinensis along the NECT.     

Elevated atmospheric CO2 alters wood production, wood quality and wood strength of Scots pine (Pinus sylvestris L) after three years of enrichment

Scots pine ( Pinus sylvestris L.) trees were grown in open top chambers for three years under ambient and elevated CO₂ concentrations. The trees were aged 3 y at the beginning of the CO₂ exposure, and the effects of the treatment on total stem volume, stem wood biomass, wood quality and wood anatomy were examined at the end of the exposure. The elevated CO₂ treatment lead to a 49% and 38% increase in stem biomass and stem wood volume, respectively. However, no significant effects of the elevated CO₂ treatment on wood density were observed, neither when green wood density was estimated from stem biomass and stem volume, nor when oven-dry wood density was measured on small wood samples. Under elevated CO₂ significantly wider growth rings were observed. The effect of elevated CO₂ on growth ring width was primarily the result of an increase in earlywood width. Wood compression strength decreased under elevated CO₂ conditions, which could be explained by significantly larger tracheids and the increased earlywood band, that has thinner walls and larger cavities. A significant decrease of the number of resin canals in the third growth ring was observed under the elevated treatment; this might indicate that trees produced and contained less resin, which has implications for disease and pest resistance. So, although wood volume yield in Scots pine increased significantly with elevated CO₂ after three years of treatment, wood density remained unchanged, while wood strength decreased. Whilst wood volume and stem biomass production may increase in this major boreal forest tree species, wood quality and resin production might decrease under future elevated CO₂ conditions.     

利用水稻重组自交系群体定位谷粒外观性状的数量性状基因

用区间作图和混合线性模型的复合区间作图两种方法,对水稻（Oryza sativa L）珍汕97和明恢63组合的重组自交系群体的谷粒外观性状－粒长,粒宽和粒形进行了数量性状基因（QTL）定位,用区间作图法在LOD≥2．4水平上（近拟于a=0.005),1998年对粒长,粒宽和粒形分别检测到6,2放2个QTLs,1999年对以上3个性状分别检测到3,2和2个QTLs,其中7个QTLs在两年均检测到,位于第3染色体RG393－C1087区间的QTL效应大,同时影响粒长和粒形,两年贡献分别为57．5％,61．4％和26．7％,29．9％,位于第5染色体RG360－C734B区间的QTL效应大,同时影响粒宽和粒形,两年贡献率分别为44．2％,53．2％和32．1％和36．0％,用混合线性模型的复合区间作图法在P＝0．005水平上,对粒长,粒宽和粒形分别检测到8,5和5个QTLs,共解释各自性状变异的58．81％,44．75％和57．47％,只检测到1个QTL与环境之间存在的显互作。     

Effects of head shape variation on growth, metamorphosis and survivorship in larval salamanders (Hynobius retardatus)

The effects of head shape variation on growth and metamorphosis in larval salamander (Hynobius retardatus) were examined by a laboratory experiment and a field experiment. In the laboratory experiment, each larva was fed equal amounts and was prevented from accessing others in both the solitary and group treatments, although chemical cues could be transmitted through water in the group treatment. The relative head width of larvae became larger in the group treatment during the early periods but having a large head width did not finally influence growth rate and days for metamorphosis. In the field experiment, larvae were allowed to contact each other directly in two density conditions. The enlarged relative head width was linked to high growth rate in the high-density treatment but not in the low-density treatment. The larval body size distribution in the high-density condition tended to be smaller, and there was a small proportion of large-sized individuals with a broad head width. Moreover, the small number of large larvae metamorphosed much earlier than the others. The mortality of larvae in high-density conditions was much higher than that in the low-density treatments. This would be a consequence of cannibalism in the high-density condition. From the experimental results obtained, it is argued that for the larvae of H. retardatus having a large head is an adaptive tactic that maximizes fitness, particularly in temporary ponds with an unpredictable environment and in crowded conditions.     

Oxygen stable isotope ratios of tree-ring cellulose: the next phase of understanding

Analysis of the oxygen isotope ratio of tree-ring cellulose is a valuable tool that can be used as a paleoclimate proxy. Our ability to use this tool has gone through different phases. The first began in the 1970s with the demonstration of empirical relationships between the oxygen isotope ratio of tree-ring cellulose and climate. These empirical relationships, however, did not provide us with the confidence that they are robust through time, across taxa and across geographical locations. The second phase began with a rudimentary understanding of the physiological and biochemical mechanisms responsible for the oxygen isotope ratios of cellulose, which is necessary to increase the power of this tool. This phase culminated in a mechanistic tree-ring model integrating concepts of physiology and biochemistry in a whole-plant system. This model made several assumptions about leaf water isotopic enrichment and biochemistry which, in the nascent third phase, are now being challenged, with surprising results. These third-phase results suggest that, contrary to the model assumption, leaf temperature across a large latitudinal gradient is remarkably constant and does not follow ambient temperature. Recent findings also indicate that the biochemistry responsible for the incorporation of the cellulose oxygen isotopic signature is not as simple as has been assumed. Interestingly, the results of these challenges have strengthened the tree-ring model. There are several other assumptions that can be investigated which will improve the utility of the tree-ring model.     

Consistency of growth response to precipitation by Pseudopiptadenia contorta in two Atlantic Forest remnants

Tree growth sensitivity to climate can vary over space and time. This variability generates inconsistency in growth response to climate, which makes it difficult to assess the effects of past climate and global climate change on tree growth. A previous short-term study of Pseudopiptadenia contorta found a consistent growth response to climate in distinct locations, which raises the question, is the growth response of P. contorta to climate consistent over the long-term? We aimed to assess whether there is a common pattern of variation in tree-ring width, build tree-ring width chronologies, and verify the consistency of the climate-growth response of P. contorta in two Atlantic Forest remnants. Wood samples were collected in Reserva Biológica de Poço das Antas (RBPA) and Reserva Biológica de Tinguá (RBT) in the state of Rio de Janeiro, Brazil. Conventional dendrochronology methods were used for cross-dating, to build chronologies and to assess the climate-growth relationship. A common growth pattern was detected for P. contorta, and two tree-ring width chronologies were constructed. A congruent growth response was found for trees of RBPA and RBT to annual and spring precipitation as well as precipitation in the rainy months. Other climate-growth relationships were detected with other precipitation and temperature variables. Considering that P. contorta is a widespread species, occurring in other Brazilian biomes and forest formations, it is a promising model for developing further dendrochronological research including regional networks of replicated site chronologies, which could facilitate the reconstruction of historical climatic series and predictions of future impacts of climate change in tropical areas.     

VS-oscilloscope: A new tool to parameterize tree radial growth based on climate conditions

It is generally assumed in dendroecological studies that annual tree-ring growth is adequately determined by a linear function of local or regional precipitation and temperature with a set of coefficients that are temporally invariant. However, various researchers have maintained that tree-ring records are the result of multivariate, often nonlinear biological and physical processes. To describe critical processes linking climate variables with tree-ring formation, the process-based tree-ring Vaganov–Shashkin model (VS-model) was successfully used. However, the VS-model is a complex tool requiring a considerable number of model parameters that should be re-estimated for each forest stand. Here we present a new visual approach of process-based tree-ring model parameterization (the so-called VS-oscilloscope) which allows the simulation of tree-ring growth and can be easily used by researchers and students. The VS-oscilloscope was tested on tree-ring data for two species (Larix gmeliniiand Picea obovata) growing in the permafrost zone of Central Siberia. The parameterization of the VS-model provided highly significant positive correlations (p < 0.0001) between simulated growth curves and original tree-ring chronologies for the period 1950–2009. The model outputs have shown differences in seasonal tree-ring growth between species that were well supported by the field observations. To better understand seasonal tree-ring growth and to verify the VS-model findings, a multi-year natural field study is needed, including seasonal observation of the thermo-hydrological regime of the soil, duration and rate of tracheid development, as well as measurements of their anatomical features.     

The potential of generalized additive modelling for the prediction of radial growth of Norway spruce from Central Germany

During the past decades managed forest ecosystems in Central Europe underwent vast changes, induced by extreme climate conditions and occasionally adverse forest management. Tree ring width patterns mirror these changes and thus have been widely examined as environmental archives and reliable empirical data sources in ‘tree growth modelling’. Dendrochronologists often suppose linear co-variation among the covariates, variable independence and homoscedasticity. Conventionally, these assumptions were achieved by eliminating biological age trends (detrending) and removing the autocorrelation from the time series (pre-whitening). Particularly detrending might be biased according to the scientific problem and sometimes inflexible age models. In this study, we tackle these issues and examine the suitability of a flexible Generalized Additive Model (GAM) on recently developed tree ring width time series of 30 Norway spruce stands (Picea abies [L.] H. Karst) from Central Germany.The model was established to simultaneously cope with the mentioned detrending issue, to unravel nonlinear climate-growth relationships and to predict mean ring width time series for spruce stands in the region. Particularly the latter was of primary interest, since recent forest planning relies on static yield tables that often underestimate the actual growth.The model reliably captured the empirical data, indicated by a small Generalized Cross Validation criterion (GCV = 0.045) and a deviance explained of 88.6 %. The flexible additive smoothers accounted for the social status of individual trees, captured low frequency variations of changing growth conditions adequately and displayed a rather flat biological age trend. The radial increment responded positively to summer season precipitation of the current and previous year. Positive temperature responses were found during the early vegetation period, whereas high summer season temperatures negatively affected the radial growth. The seasonal transition from spring to summer in June induced a shift in the climate response of the linear predictor, leading to a distinct negative effect of temperature and a no-role of precipitation on the linear predictor.Most important, utilizing the calibrated GAM for the purely climate-driven prediction of mean ring width time series from five independent spruce sites revealed proper coherencies. Herein, the mean ring width for sites located within the climatic-optimum for spruce growth were more exactly predicted than for sites with adverse spruce growth conditions. In addition, large mean ring widths were systematically underestimated, whereas small mean ring widths were precisely predicted. Overall, we strongly recommend GAMs as a powerful tool for the investigation of nonlinear climate-growth relationships and for the prediction of radial growth in managed forest ecosystems.