Aerial decay influence on the stable oxygen and carbon isotope ratios in tree ring cellulose

Sub-fossil wood is often affected by the decaying process that introduces uncertainties in the measurement of oxygen and carbon stable isotope composition in cellulose. Although the cellulose stable isotopes are widely used as climatic proxies, our understanding of processes controlling their behavior is very limited. We present here a comparative study of stable oxygen and carbon isotope ratios in tree ring cellulose in decayed and non-decayed wood samples of Swiss stone pine (Pinus cembra) trees. The intra-ring stable isotope variability (around the circumference of a single ring) was between 0.1 and 0.5‰ for δ¹⁸O values and between 0.5 and 1.6‰ for δ¹³C values for both decayed and non-decayed wood. Observed intra-tree δ¹⁸O variability is less than that reported in the literature (0.5–1.5‰), however, for δ¹³C it is larger than the reported values (0.7–1.2‰). The inter-tree variability for non-decayed wood ranges between 1.1 and 2.3‰ for δ¹⁸O values, and between 2 and 4.7‰ for δ¹³C values. The inter-tree differences for δ¹⁸O values are similar to those reported in the literature (1–2‰ for oxygen and 1–3‰ for carbon) but are larger for δ¹³C values. We have found that the differences for δ¹⁸O and δ¹³C values between decayed and non-decayed wood are smaller than the variation among different trees from the same site, suggesting that the decayed wood can be used for isotopic paleoclimate research.     

Stories hidden in tree rings: A review on the application of stable carbon isotopes to dendrosciences

During the last 25 years, the dendrochronology community has benefited from the application of stable carbon isotopes in tree rings to answer a number of research questions, which has resulted in an exponential burst in the number of publications related to this discipline. Here, we perform a literature review of the most influential topics (scope, methodology, targeted species, and climatic signals) that have shaped the research agenda and its impact on the scholarly output over the recent decades. Based on a total of 550 publications, we observed that: (1) conifers are the most investigated tree functional type, being included in over two-thirds of studies; (2) although being a subject of debate, the material of choice for carbon isotope analyses is still cellulose, for which the extraction procedure has been refined with methodological improvements over the years; (3) a shift in the application of carbon isotopes has occurred from proxies of climatic information for paleoclimatic reconstructions to tools for the understanding of short- and long-term tree functioning; and (4) such shift in research scope is apparently linked to an increasing number of publications showing drought-related signals governing isotope time series in the context of current climate change. Besides, we also assessed the number and outcome of publications analyzing ¹³C-derived intrinsic water-use efficiency (WUE_i) trends within the framework formulated by Saurer et al. (2004). We found that leaf intercellular CO₂ concentration responding proportionally to the increase in atmospheric CO₂ is the most common scenario reported across continents, but with changing importance relative to other scenarios depending on the biome examined. We also detected that climate plays a dominant role over any potential CO₂ fertilization linked to increasing WUE_i. Looking for new and thrilling research avenues, future studies should further examine δ¹³C fluctuations at intra-annual resolution, explore its links to wood characteristics, and disentangle δ¹³C signals of the distinct wood constituents for a better understanding of tree functioning at varying spatiotemporal scales, also benchmarking vegetation models of different complexities.     

Wood density as a proxy of drought-induced forest dieback in silver fir

Drought-induced dieback is a matter of global concern. It has been widely reported and could compromise the climate warming mitigation potential of forests. That is why we need reliable early-warning proxies to achieve better forecasts of forest dieback and tree death. Tree-ring data can provide some of these needed proxies. Here I propose considering minimum (MND) and maximum (MXD) wood density values as proxies of tree vulnerability against drought. This hypothesis is evaluated in silver fir (Abies alba) forests from the western Spanish Pyrenees showing ongoing dieback processes after the severe 1985 drought. MXD increased in response to warm summer conditions in 1985 whereas MND increased in response to growing-season water deficit in 1986. The average between prior MXD (MXD_t-1) and subsequent MND (MND_t) could be used to detect severe drought impacts and forecast dieback.     

白桦天然种群木材化学成分的地理变异与相关性研究

以东北地区5个天然白桦种群为研究对象,进行了木材的化学成分分析。结果表明：除1% NaOH抽出物、综纤维素、聚戊糖外,种群间化学成分含量差异都显著,并且各种群变异较大,这为白桦纸浆材种群间选择和种群内选择提供了可能。白桦天然种群间灰分与苯醇抽出物含量呈显著正相关,综纤维素与聚戊糖含量呈显著正相关。灰分和抽出物含量的变异与经度呈一定程度负相关,综纤维素和聚戊糖与纬度呈一定程度正相关,木素与纬度呈一定程度负相关。这表明,选择较高经纬度地区的白桦,可以降低灰分、抽出物、木素含量,提高综纤维素和聚戊糖含量。     

Plant phenological data and tree-rings as palaeoclimate indicators in south-west Finland since AD 1750

Plant phenological data and tree-rings were tested for their palaeoclimatic value in south-west Finland since AD 1750. The information from fragmentary, partly overlapping, partly non-systematically biased plant phenological records of 14 different phenomena (a total of 3,144 observations) was combined into one continuous time series of phenological indices. All site- and phenomenon-specific series were standardized to present an average of zero and standard deviation of one. The mean phenomenon-specific series were then averaged as arithmetic means for annually resolved time series representing the variability in the particular plant phenomenon. Consequently, each phenomenon-specific mean series was based on spatially normalized site-specific index series. These series were compared to each other, living-tree and subfossil tree-rings, and to early and modern meteorological time series. Phenological indices showed strong positive correlation with February to June temperatures. On the other hand, the correlations between phenological indices and precipitation data were around zero. Analysis using time-dependent running correlations showed non-stationary relationship between the tree-rings and phenological indices and observed spring temperatures. The skill of phenological data for reconstructing the spring temperatures was statistically proved.     

转UGPase基因喜树木材化学成分与生长速率研究

分析了田间栽培条件下2年生转UGPase基因喜树与对照株的木材化学成分与生长速率。结果表明,转UGPase基因喜树综纤维素含量达到78.87%,比对照株相比提高了2.23%;纤维素含量为36.34%,与对照株相比没有明显提高;木质素含量为15.05%,较对照株降低了1.75%;两者的灰分含量均较低且无显著差异;冷、热水抽提物含量为7.62%与10.17%,分别提高了2.04%与2.13%;1% NaOH抽提物含量为27.13%,提高了1.27%。因此,就综纤维素、木质素、灰分含量而言,转UGPase基因喜树为优质纸浆材,水抽提物和1% NaOH抽提物的含量略高,在纸浆生产中需加以重视。本文还对转UGPase基因喜树与对照株的株高、基径、生物量进行了动态监测,结果表明,从5月25日到11月10日的生长季中,其株高平均增加121 cm,对照株平均仅67.8 cm,株高生长速率提高了78.47%;基径平均增加1 792 cm,对照株平均仅0.532 8 cm,提高了236.37%;地上部分生物量的积累与对照相比提高了322.61%,即转入UGPase基因使喜树生长速率显著提高。因此,虽然转UGPase基因喜树的综纤维素和纤维素含量没有明显提高,但其生长速率快,生物量增长显著,间接提高了纤维素与喜树碱的产量。因此,转基因喜树较普通喜树更符合纸浆材速生、纤维素含量高和产量高、木质素含量低的基本要求,可在生产中进一步推广。     

Dendrogeomorphic reconstruction of the seasonal timing and rainfall threshold for debris slide occurrence in eastern Canada

Debris slide occurrence on treed slopes of northeastern North America is still poorly documented, despite their abundance and their potential to change mountainous landscapes in short periods of time. To provide new information on their spatiotemporal dynamics, a study was undertaken in debris slide paths in the Wildlife Reserve of Port-Cartier-Sept-Iles, on the Québec North-Shore region of eastern Canada. Tree-ring dating of growth anomalies (impact scars and reaction wood) in nine debris slides allowed the identification of four debris slide events that occurred in 2003, 2006, 2008, and 2010. By comparison to other hillslope processes such as snow avalanches and debris flows, debris slides produce a very strong tree-ring signal. Therefore they do not require a large sample size considering also that they do not occur twice at the same place. The position of growth anomalies within individual tree rings allowed to determine the timing of the debris slide events: injuries located within a ring correspond to debris slides occurring during the growing season, whereas injuries located between the end of a ring and the beginning of the following ring were caused by debris slides occurring during the dormant season. The meteorological data indicate that a daily precipitation of 70 mm appears usually sufficient for the occurrence of debris slides.     

Tree rings as a surrogate for economic stress – an example from the Puna of Jujuy, Argentina in the 19th century

This paper illustrates the use of tree-ring indices as an indicator of economic stress. In the 19th century the rural economy in the Puna of Jujuy, Northwestern Argentina was based on livestock (llamas and sheep), and was heavily dependant on the availability of pasture and water in this arid landscape. In the absence of traditional indicators of socioeconomic stress, we used tree-ring indices from moisture sensitive trees (Juglans australis Griseb. and Polylepis tarapacana Phil.) as a proxy for droughts and their related economic stresses. Examining the relationship between population mortality and ring-width indices allows inferences to be drawn about the relative importance of environmental and sociopolitical factors in determining mortality patterns that contributed to the depopulation of this area in the late 19th century.     

Radial Gradients in Wood Specific Gravity,Water and Gas Content in Trees of a Mexican Tropical Rain Forest

Cell walls, water, and gas that have mechanical and physiological functions in wood, and wood specific gravity (WSG) is related to demographic traits. To understand variation in wood structure and function, we analyzed radial changes in WSG, in the gas and the water fractions from trees growing in four different habitats in a southern Mexican rain forest. Mean WSG was 0.55 ± 0.16, slightly lower than reported for other tropical forests. In 27 species, WSG decreased and in two species, it increased from pith to bark with a strong (r² = 0.65) negative correlation between WSG in the center of the tree and the radial WSG gradient. Habitat had some effect on mean WSG and trees growing on karst had significantly higher WSG than the same species growing on alluvial soil. The cell wall, water, and gas fractions accounted for 35 percent (range: 16–50), 42 percent (28–65), and 23 percent (2–56), respectively, of wood volume, with a negative correlation between the gas and the cell wall and between the gas and the water fractions, but not between the cell wall and water fractions. Radially increasing WSG is advantageous for pioneer trees with fast initial growth. We found that the water displacement method may result in biased WSG estimates. To increase the accuracy of WSG data, we suggest to measure sample volume geometrically using a constant diameter (that of the borer tip), to include radial variation in WSG, and to consider for possible site effects on species‐specific WSG.     

Tree rings as criteria for selection of timber for building of chapels in the Republic of Karelia

Data on the quality of timber used for building chapels – small buildings for public worship, enabled determination of visual criteria used for the selection of timber in the Republic of Karelia, located in the north-western part of the Russian Federation.It was revealed that as for the majority of timber structures in the region, Scots pine (Pinus sylvestris L.) logs were selected for the chapels. Trees perceived as 'Holy' such as spruce (Picea abies Kr.), were not used in these worship structures, in contrast to practices in the neighboring Leningrad Region. The age of the logged trees was 100–150 years, with a high proportion of young trees.Data obtained proved convincingly that compared with huge parish churches, selection of timber for these small chapels was not so strict. Multivariate analysis of variance showed that an ethnological factor played a significant role in the selection of wood for the buildings. Mature trees with narrow tree rings were preferred for worship structures preserved in villages populated by Karelians – the Baltic-Finnic tribe living in the region since ancient times.In villages with a dominantly Russian population, young pines with wide annual rings were dominantly used. A correlation between the height of the structures and the average diameter of the logs used was found with the coefficient of determination high in Karelian villages and lower in Russian villages.     

Anatomically preserved cordaitalean trees from the Pennsylvanian of Yangquan City,Shanxi Province,and their implication for a perhumid climate in North China Block

Fifty-six cordaitalean trunks with anatomical features are discovered and described from the Moscovian (Pennsylvanian) Benxi Formation in Yangquan City, Shanxi Province, North China. They are allochthonously preserved in fluvial channel deposits and classified into two types based on the anatomy. The first type is characterized by a solid and heterocellular pith, endarch primary xylem and pycnoxylic secondary xylem with araucarian radial tracheidal pits and araucarioid cross-field pitting. The second type contains a septate pith and a pycnoxylic secondary xylem which is comparable to that of the first type. Primary xylem is absent in the second type. The diameter of these trunks ranges from 0.11 m to 0.55 m. The largest tree is estimated to be 29.96 m high using an allometric approach. The trunks represent the oldest and largest trees from the North China Block during the Pennsylvanian due to the absence of Silurian, Devonian, and Mississippian there. The fossil evidence shows that cordaitaleans were large arborescent trees growing on clastic substrates in the Cathaysia during the Pennsylvanian. Their occurrence from the upper Pennsylvanian in North China Block suggests that the previously reported diversity of cordaitaleans, which were estimated based on impressions, is a gross underestimate. The absence of growth rings in the trunks and co-occurrence of arborescent lycopsids in the same interval, together with coal seams and bauxite around the fossil-bearing horizons, indicate that the trees grew under perhumid tropical conditions.     

Diverging growth and resilience of Pinus tabulaeformis and Pinus massoniana to droughts in north-south transition zone,central China

Climate transition zone is a sensitive area of climate change and ecological transition where forests are vulnerable to climate extremes. Extreme droughts are increasing in frequency and magnitude under climate change, resulting in structure and function changes of forest ecosystems. Here, to analyze climate-growth relationships and quantify tree resilience to extreme droughts, we developed six tree-ring-width chronologies from P. tabulaeformis and P. massoniana sampling sites in Mt. Jigong region, Central China. The results indicated that all chronologies from the two species had good consistency, precipitation in current April and mean temperature in current August or mean minimum temperature from current August to October were the main limiting factors of the two tree species growth, but the responses of P. massoniana ring-width to climatic factors was more complex than that of P. tabulaeformis. The results also showed that tree growth of 1999–2005 was the lowest growing period during 1979–2018, and P. massoniana grew better than P. tabulaeformis before 2005 and vice versa after 2005. Comparing low growth years of trees, we identified to study tree growth resilience. The calculations from 1988, 1999–2005 and 2011 drought years indicated that P. tabulaeformis had more increased resilience to extreme droughts than that of P. massoniana, and the two species had stronger ecological recovery and resilience under global warming and non-extreme drought conditions in the recent 40 years. These results have implications for predicting tree resilience and identifying tree species in heterogeneous forest landscapes vulnerable to future climate change in climatic transition zone.     

Structural Characterization and Chemical Classification of Some Bryophytes Found in Latvia

Bryophytes are the second largest taxonomic group in the plant kingdom; yet, studies conducted to better understand their chemical composition are rare. The aim of this study was to characterize the chemical composition of bryophytes common in Northern Europe by using elemental, spectral, and non‐destructive analytical methods, such as Fourier transform IR spectrometry (FT‐IR), solid‐phase ¹³C‐NMR spectrometry, and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), for the purpose of investigating their chemotaxonomic relationships on the basis of chemical‐composition data. The results of all these analyses showed that bryophytes consist mainly of carbohydrates. Judging by FT‐IR spectra, the OH groups in combination of C? O groups were the most abundant groups. The ¹³C‐NMR spectra provided information on the presence of such compounds as phenolics and lipids. It was found that the amount of phenolic compounds in bryophytes is relatively small. This finding definitely confirmed the absence of lignin in the studied bryophytes. Cluster analysis was used to better understand differences in the chemical composition of bryophyte samples and to evaluate possible usage of these methods in the chemotaxonomy of bryophytes.     

Screening of Polish Fir Honeydew Honey Using GC/MS,HPLC‐DAD,and Physical‐Chemical Parameters: Benzene Derivatives and Terpenes as Chemical Markers

GC/MS of headspace solid phase micro extraction (HS‐SPME) and solvent extractives along with targeted HPLC‐DAD of Polish fir (Abies alba Mill .) honeydew honey (FHH), were used to determine the chemical profiles and potential markers of botanical origin. Additionally, typical physical‐chemical parameters were also assigned. The values determined for FHH were: conductivity (1.2 mS/cm), water content (16.7 g/100 g), pH (4.5), and CIE chromaticity coordinates (L* = 48.4, a* = 20.6, b* = 69.7, C* = 72.9, and h° = 73.5). FHH contained moderate‐high total phenolic content (533.2 mg GAE/kg) and antioxidant activity (1.1 mmol TEAC/kg) and (3.2 mmol Fe²⁺/kg) in DPPH and FRAP assays. The chemical profiles were dominated by source plant‐originated benzene derivatives: 3,4‐dihydroxybenzoic acid (up to 8.7 mg/kg, HPLC/honey solution), methyl syringate (up to 14.5%, GC/solvent extracts) or benzaldehyde (up to 43.7%, GC/headspace). Other markers were terpenes including norisoprenoid (4‐hydroxy‐3,5,6‐trimethyl‐4‐(3‐oxobut‐1‐enyl)cyclohex‐2‐en‐1‐one, up to 20.3%, GC/solvent extracts) and monoterpenes, mainly linalool derivatives (up to 49%, GC/headspace) as well as borneol (up to 5.9%, GC/headspace). The application of various techniques allowed comprehensive characterisation of FHH. 4‐Hydroxy‐3,5,6‐trimethyl‐4‐(3‐oxobut‐1‐enyl)cyclohex‐2‐en‐1‐one, coniferyl alcohol, borneol, and benzaldehyde were first time proposed for FHH screening. Protocatechuic acid may be a potential marker of FFH regardless of the geographical origin.     

Tree growth and climate sensitivity in open and closed forests of the southeastern Tibetan Plateau

The creation of forest openings is a frequently observed phenomenon in many types of forests. On the southeastern Tibetan Plateau, where the average elevation is greater than 4000 m above sea level, differences in tree growth between forest stands with openings and completely closed stands are poorly characterized. Here, we presented a dendrochronological study of Tibetan juniper (Juniperus tibetica Kom.) and Sikkim spruce (Picea spinulosa (Griff.) Beissn.) in an open and a closed stand, near Qamdo of eastern Tibet. We found that the growth of juniper responded to climate in a similar way in the open and closed stands, and was positively correlated with temperature from October to January and with the Palmer Drought Severity Index (PDSI) from September to June. In contrast, the growth of spruce responded to climate differently in the open and closed stands: growth was positively correlated with the PDSI from September to May in the open stand, whereas it was positively correlated to November and December temperatures (of the prior year) and current June temperature in the closed stand. Interannual variation in, and standard deviations among, juniper tree ring widths were similar in both stands for the past four centuries, whereas they differed in spruce over the past two centuries, particularly in the 1900s. These results suggest that juniper tree ring growth is less sensitive to stand structure than that of spruce, thus providing more reliable climate signals. The data obtained from our study will help forest managers understand the ecology of juniper and spruce in open and closed stands and are therefore useful for management planning.     

Method for detecting tree ring boundary in conifers and broadleaf trees using Mask R-CNN and linear interpolation

As tree rings can reveal various information regarding climate and environmental factors, increasing research is being conducted on them. Although tree ring analysis software such as Windendro has been applied, research on the development of analysis software using image preprocessing algorithms and deep learning is recently being attempted as computer vision technology. In this study, Mask R-CNN and linear interpolation were applied from images collected using a smartphone (SM-G973, Samsung, Suwon) and a scanner (CanoScan 9000F, Canon, Otaku) to propose an effective method for detecting tree ring boundaries. Pitch pine (Pinus rigida), Korean pine (Pinus koraiensis), white birch (Betula platyphylla), and cork oak (Quercus variabilis) were selected as tree species. Of the 300 images, 240 were classified as training data and 60 as validation data. As a result of learning, smartphones detected 86.0 % (381 ring boundaries) of the rings in pitch pine, 82.1 % (367 ring boundaries) in Korean pine, 84.7 % (309 ring boundaries) in white birch, and 78.7 % (318 ring boundaries) in cork oak. The scanner detected 93.2 % (413 ring boundaries) of the rings in pitch pine, 90.8 % (405 ring boundaries) in Korean pine, 88.2 % (322 ring boundaries) in white birch, and 89.4 % (361 ring boundaries) in cork oak. In particular, the smartphone showed satisfactory results of 84.7 % and 78.7 % for detecting tree ring boundaries of white birch and cork oak, where the boundaries of the rings were unclear. In the annual growth analysis results, both smartphones and scanners were statistically insignificant, and there was no difference compared with those of Windendro. Therefore, Mask R-CNN might be an effective approach for tree ring boundary detection as it showed satisfactory results, even with smartphones. In addition, although there was distortion in cases where images were acquired with a circular lens, there was no statistically significant difference from Windendro results. Thus, Mask R-CNN and linear interpolation can be used for tree ring boundary detection and growth measurement.     

Development of facies and C/O-isotopes in transects through the Ludlow of Gotland: Evidence for global and local influences on a shallow-marine environment

Summary The Silurian of Gotland is characterized by repeated changes in depositional facies development. The deposition of uniform sequences of micritic limestones and marls was interrupted four times by the growth of reef complexes and the formation of expanded carbonate platforms. Coinciding with these, often abrupt, facies changes extinction events occurred which predominantly affected nektonic and planktonic organisms. Ratios of carbon- and oxygen-isotopes covary with the facies development. Periods in which the deposition of limestonemarl alternations prevailed are characterized by relatively low C- and O-isotope values. During periods of enhanced reef growth isotope values are high. For these changes,Bickert et al. (1997) assume climatic changes between humid “H-periods”, with estuarine circulation systems and cutrophic surface waters with decreased salinity in marginal seas, and arid “A-periods”, with an antiestuarine circulation and oligotrophic, stronger saline surface waters. In order to separate local and regional influences on the isotopic development from the global trend, the interactions between facies formation and isotope record have to be clarified. For this purpose, the patterns of isotope values in the upper part of the Silurian sequence on Gotland (upper Wenlock —upper Ludlow) has been determined and stratigraphically correlated along four transects through different facies areas. Facies formation during this time interval was investigated by differentiation and mapping of twelve facies complexes in the southern part of Gotland. These include shelf areas, reef complexes with patch reefs and biostromes, backreef facies, and marginal-marine deposits. The good correspondence between the carbon-isotope records of the four transects suggests that local environmental conditions in the different facies areas did not influence the δ¹³C values. Therefore, a supra-regional or even global mechanism for the C-isotope variations is likely. In contrast to carbon istopes, the oxygen-isotope values of the four transects generally show parallel trends, but higher variabilities and in parts distinctly deviating developments with a trend to more negative values. These are interpreted as an effect of local warming in small shallow-water areas which developed during arid periods in reef complexes and backreef areas. The boundaries between A-periods and H-periods, as defined by δ¹³C values, which are interpreted as isochrones, can be mapped. From the upper Homerian to the Pridolian six parastratigraphic isotope zones are defined which only partly match the stratigraphic division ofHede (1942, 1960). The isotope stratigraphy results in an improved correlation between the shallow and marginal-marine areas in the eastern part of Gotland and the uniform shelf areas at the west coast of the island. Furthermore, a detailed relationship between the development of carbon and oxygen isotope ratios, the carbonate facies formation, and the succession of palaeontological events could be observed. At the transition from H-periods to A-periods, major extinction events occurred prior to the first increase of δ¹³C and δ¹⁸O values. Extinction events affected conodonts, graptolites, acritarchs, chitinozoans, and vertebrates and resulted in impoverished nektonic and planktonic communities. The reef-building benthos was less affected. Parallel to a first slight increase of isotope values, facies began to change, and reefs developed in suitable locations. The subsequent rapid increase of C- and O-isotope values occurred contemporarily with strong facies changes and a short-term drop of sea-level. Oligotrophic conditions in the later stages of A-periods led to strong reef growth and to an expansion of carbonate platforms. The transitions from A-periods to H-periods were more gradual. The δ¹³C values decreased slowly, but reef growth continued. Later the reefs retreated and were covered by the prograding depositional facies of shelf areas. The diversity of planktonic and nektonic communities increased again. The close relationship between facies formation, palaeontological events and isotope records in the Silurian suggests common steering mechanisms but gives no indication of the causes for the repeated extincion events related to H-period/A-period transitions. Especially the observation, that strong extinctions occurred prior to changes of isotope values and facies, points to causes that left no signals in the geological record. Hypothetical causes like collapse of trophical nets, anoxias, or cooling events are not evident in the sediment record or do not fit into the regular succession of period transitions.     

Responses of radial growth and stable carbon isotopes to climate in the northern Tianshan Mountains

Climate change has profound effects on forest ecosystems. Schrenk spruce (P. schrenkiana) is a natural conifer species endemic to the arid inland areas of Asia. In this study, the relationship between tree-ring parameters of P. schrenkiana and major meteorological factors were analyzed, and the main limiting factors for tree radial growth and stable carbon isotope fractionation were explored. Our results indicate that moisture stress before and during the growing season have an important influence on radial growth of P. schrenkiana, especially, the correlation coefficient between tree-ring width and vapor pressure deficit (VPD) from previous August to current July is as high as −0.622 (n = 51, p < 0.01). Collinearity analysis further supports the conclusion that the limiting factor for the radial growth of P. schrenkiana is moisture. Although the correlation analysis results show that the tree-ring δ¹³C_corr is significantly positively correlated with sunshine duration (SD), additional analysis based on first order difference variables suggests that the climate factor may not be the only limiting factor for the stable carbon isotope fractionation of tree rings in the Sayram Lake Basin. This lays the foundation for the assessment of forest management practices and carbon sink capacity in light of future climate change.     

与杨树木材密度、纤维性状相关的SSR分子标记

通过对美洲黑杨 (Populusdeltoides)×青杨 (P .cathayana)的 68个F2 、双亲及其 4个F1无性系田间随机区组设计 ,5次重复 ,分析了与木材材性有关的木材密度、纤维长、纤维宽以及微纤丝角等性状。结果表明 :纤维长有明显的杂种优势 ,控制该性状表现的基因之间具有正效应的互作 ;控制木材基本密度的基因之间具有负效应的互作。结合SSR分子标记结果 ,采用单因素方差分析法进行标记与性状的相关分析 ,共找到与木材密度、纤维长、纤维宽以及微纤丝角相关联的标记分别为 5、7、4、2个 ;青杨在这 4个材性性状方面也具有对性状起贡献的标记 ,如与木材密度相关的PMGC2 873 1(贡献率 4 88% )标记 ,与纤维长相关的PMGC456 3 (贡献率 2 2 96% )、PMGC2 70 2 2 (贡献率9 17% )标记 ,与纤维宽相关的PMGC2 40 8 1(贡献率 7 18% )标记 ,与微纤丝角相关PMGC2 52 5 1(贡献率 16 59% )标记 ,在育种中如果能正确加以利用 ,也可起到一定的材性改良作用