Development of tree-ring width chronologies and tree-growth response to climate in the mountains surrounding the Issyk-Kul Lake,Central Asia

Three tree-ring width chronologies were developed from 75 Picea schrenkiana trees ranging from low- to high-elevation in the mountains surrounding the Issyk-Kul Lake, Northeast Kyrgyzstan. The reliable chronologies extend back to the mid-18th and late-19th centuries. Spatial correlation analysis indicates that the chronologies for the relatively high-elevation trees contain large-scale climatic signals, while the chronology at relatively low elevation may reflect the local climate variability. The results of the response of tree growth to climate show that these chronologies contain an annual precipitation signal. Furthermore, the influence of temperature indicates mainly moisture stress that is enhanced with rising elevation. The tree-ring records also captured a wetting trend in eastern Central Asia over the past decades. These new tree-ring width chronologies provide reliable proxies of precipitation variability in Central Asia and contribute to the International Tree-Ring Data Bank.     

芦芽山阳坡不同海拔华北落叶松径向生长对气候变化的响应

为研究树木生长对气候变化的响应状况,选取芦芽山阳坡的3个海拔高度建立了华北落叶松(Larix principis-rupprechtii)的树轮宽度年表。年表的统计参数表明,3条年表均为研究气候信息的可靠资料。结果表明,芦芽山阳坡华北落叶松的径向生长和生长与气候的关系均具有海拔差异,中海拔(2440 m)和高海拔(2540 m)的华北落叶松具有相似年际生长变化,而二者均与低海拔(2330 m)华北落叶松的年际生长不同。低海拔华北落叶松的生长与4月平均气温和上一年11月降水量显著负相关,而中海拔和高海拔的生长均与上一年10月平均气温和6月降水量显著负相关。通过年表与气候因子之间的滑动相关分析发现,3个海拔高度华北落叶松生长与气候因子的关系均不稳定,生长与气温条件之间的显著相关关系是随着气温升高而出现的。气温的升高引起了华北落叶松生长与气温因子关系的海拔差异,以及径向生长的海拔差异。这一结果对于气候变化对植被垂直梯度影响的研究具有一定参考价值。     

Tree-ring growth of Gmelin larch under contrasting local conditions in the north of Central Siberia

While the forest-tundra zone in Siberia, Russia has been dendroclimatologically well-studied in recent decades, much less emphasis has been given to a wide belt of northern taiga larch forests located to the south. In this study, climate and local site conditions are explored to trace their influence on radial growth of Gmelin larch (Larix gmelinii (Rupr.) Rupr.) trees developed on permafrost soils in the northern taiga. Three dendrochronological sites characterized by great differences in thermo-hydrological regime of soils were established along a short (ca. 100 m long) transect: on a river bank (RB), at riparian zone of a stream (RZ) and on a terrace (TER). Comparative analysis of the rate and year-to-year dynamics of tree radial growth among sites revealed considerable difference in both raw and standardized tree-ring width (TRW) chronologies obtained for the RZ site, characterized by shallow soil active layer depth and saturated soils. Results of dendroclimatic analysis indicated that tree-ring growth at all the sites is mostly defined by climatic conditions of a previous year and precipitation has stronger effect on TRW chronologies in comparison to the air temperatures. Remarkably, a great difference in the climatic response of TRW chronologies has been obtained for trees growing within a very short distance from each other. The positive relation of tree-ring growth with precipitation, and negative to temperature was observed in the dry site RB. In contrary, precipitation negatively and temperature positively influenced tree radial growth of larch at the water saturated RZ. Thus, a complicate response of northern Siberian larch forest productivity to the possible climate changes is expected due to great mosaic of site conditions and variability of environmental factors controlling tree-ring growth at different sites. Our study demonstrates the new possibilities for the future dendroclimatic research in the region, as various climatic parameters can be reconstructed from tree-ring chronologies obtained for different sites.     

A dendroclimatic analysis of mountain hemlock (Tsuga mertensiana) ring-width and maximum density parameters,southern British Columbia Coast Mountains,Canada

The growth of mountain hemlock trees in Pacific North America demonstrates a complex relationship to two or more seasonal environmental variables. In order to examine the radial growth response of mountain hemlock to subseasonal climate variables, ring-width and X-ray densitometric analyses were used to construct intra-annual dendroclimatic records. The intent was to highlight the difference between the dendroclimatic outcomes of standard ring-width analyses to those derived from density chronologies collected at high elevation locations in the British Columbia Coast Mountains. This study highlights the importance of using multiple tree-ring parameters to better define the complex growth behaviour in mountain hemlock trees for the construction of more robust proxy climate records. Tree-ring chronologies from three sites were used to describe the inherent climate-growth trends. Maximum tree-ring density values provided a robust data series for constructing site-specific proxy records of late-summer temperature. Annual ring-width measurements provided independent proxies of spring snowpack trends. Significant decreases in temperature and an increase in snowpack depth during the early 1700s and early 1800s coincides with documented PDO phases and Little Ice Age glacier advances. Identification of early and late growing season climate signals within mountain hemlock trees demonstrates the value of documenting the characteristics of multiple tree ring parameters in future dendroclimatic studies.     

Comparison of whole wood and cellulose carbon and oxygen isotope series from Pinus nigra ssp. laricio (Corsica/France)

Stable isotopes in tree rings have widely been used for palaeoclimate reconstructions since tree rings record climatic information at annual resolution. However, various wood components or different parts of an annual tree-ring may differ in their isotopic compositions. Thus, sample preparation and subsequent laboratory analysis are crucial for the isotopic signal retained in the final tree-ring isotope series used for climate reconstruction and must therefore be considered for the interpretation of isotope–climate relationships. This study focuses on wood of Corsican Pine trees (Pinus nigra ssp. laricio) as this tree species allows to reconstruct the long-term climate evolution in the western Mediterranean. In a pilot study, we concentrated on methodological issues of sample preparation techniques in order to evaluate isotope records measured on pooled whole tree-ring cellulose and whole tree-ring bulk wood samples. We analysed 80-year long carbon and oxygen chronologies of Corsican Pine trees growing near the upper tree line on Corsica. Carbon and oxygen isotope records of whole tree-ring bulk wood and whole tree-ring cellulose from a pooled sample of 5 trees were correlated with the climate parameters monthly precipitation, temperature and the self-calibrating Palmer Drought Severity Index (sc-PDSI). Results show that the offsets in carbon and oxygen isotopes of bulk wood and cellulose are not constant over time. Both isotopes correlate with climate parameters from late winter and summer. The carbon and oxygen isotope ratios of cellulose are more sensitive to climatic variables than those of bulk wood. The results of this study imply that extraction of cellulose is a pre-requisite for the reconstruction of high-resolution climate records from stable isotope series of P. nigra ssp. laricio.     

中国祁连山西段青海云杉树轮密度记录的气候信号

树轮气候学是研究过去气候变化的重要手段之一。以往研究表明,树轮密度是生长季温度的重要代用资料。本文建立了祁连山西段青海云杉132～135年的树轮最大密度年表、树轮最小密度年表、树轮晚材平均密度年表和树轮早材平均密度年表,比较了不同密度年表指示的最优气候信号及其季节组合,评估了其作为气候代用资料的潜力与价值。结果表明:树轮晚材平均密度和树轮早材平均密度对于树木生长季气候信号的响应远低于树轮最大密度和树轮最小密度;树轮早材平均密度和树轮最小密度与帕尔默干旱指数有很强的联系,表明树轮早材平均密度和树轮最小密度有成为干旱代用指标的潜力。     

Dendroclimatic signals in the pine and spruce chronologies in the Solovetsky Archipelago

Searching for a robust tree-ring parameter useful for paleoclimatic purposes is one of the most demanding topics in the modern paleoscience. Since Blue Intensity has already expressed itself in different geographical locations all over the world as a possible replacement for maximum density, close attention is paid to investigate features of the inferred signal. The Solovki Islands is a unique location in Northern Russia where two important factors that make this territory attractive for developing a long tree-ring chronology have been met: modern long-living trees and building activities using old trees that were started by monks in the middle of the 16th century. The main goal of the research is to develop pine and spruce chronologies based on tree-ring width (TRW) and delta Blue Intensity (dBI) and to assess the ability of these parameters to be used as climate predictors. As a result, 14 conifer chronologies from 7 sites (4 for pine and 3 for spruce) were developed. The composite pine and spruce chronologies span a period of 474 and 378 years each. Cross-correlation of dBI-based chronologies of both conifers is high (r = up to 0.71 while for TRW-based chronologies it is lower on average (−0.18 to 0.63). Intra-species correlation of TRW chronologies in some cases achieved even negative values (r = −0.18. Discrepancies found between TRW chronologies of pine and spruce could be explained by differences in climatic signals. Response function analysis with monthly temperatures revealed that growth of pine depends on the previous August, while spruce has a temporally stable and strong relation to June temperatures. Compared to TRW, dBI-based chronologies have a high correlation with summer temperatures (r = 0.64 and 0.66 for spruce and pine, respectively). Presented research points out the importance of the response function analysis suggesting that depending on goals of the study several tree-ring parameters could be used, e.g., tree-ring width of spruce responses to June temperatures, while dBI to the whole summer.     

黄土高原南北样带尺度人工刺槐林对气候响应的敏感性分析

根据黄土高原南北样带尺度的人工刺槐林(Robinia pseudoacacia)的年轮宽度资料,分析了该地区刺槐树木生长趋势,以及刺槐年表对气候响应随降雨梯度变化规律。研究结果表明延安以北的刺槐样点(绥德、神木)年轮指数近期趋于下降,树木有生长衰退现象;而延安以南刺槐样点(延安、富县、宜君、永寿)年轮指数近期趋于上升,树木无生长衰退现象。气候响应结果表明,刺槐年表对气候响应均以延安样点最为敏感,表现年表与温度的负相关关系,以及年表与降雨和干旱指数的正相关关系,而延安以北和以南刺槐样点对气候响应敏感性均较低。黄土高原中部延安地区地处森林草原过渡带,刺槐生长对外界环境变化最为敏感,年表中气候信号也较强;延安以南地区地处森林植被带,气候条件较为适宜刺槐林生长,因而年表中气候信号较弱;延安以北地区地处草原植被带,气候条件比较恶劣,刺槐生长对干旱气候已有一定适应性特征,因而年表中气候信号也较弱。     

Individual and time-varying tree-ring growth to climate sensitivity of Pinus tabuliformis Carr. and Sabina przewalskii Kom. in the eastern Qilian Mountains, China

Individual tree-ring width chronologies and mean chronologies from Pinus tabuliformis Carr. (Chinese pine) and Sabina przewalskii Kom. (Qilian juniper) tree cores were collected and analyzed from two sites in the eastern Qilian Mountains of China. The chronologies were used to analyze individual and time-varying tree-ring growth to climate sensitivity with monthly mean air temperature and total precipitation data for the period 1958–2008. Climate–growth relationships were assessed with correlation functions and their stationarity and consistency over time were measured using moving correlation analysis. Individuals’ growth–climate correlations suggested increased percentages of individuals are correlated with certain variables (e.g., current June temperature at the P. tabuliformis site; previous June, December and current May temperature and May precipitation at the S. przewalskii site). These same climatic variables also correspond to the mean chronology correlations. A decreased percentage of individuals correlated with these climatic variables indicates a reduced sensitivity of the mean chronology. Moving correlation analysis indicated a significant change over time in the sensitivity of trees to climatic variability. Our results suggested: (1) that individual tree analysis might be a worthwhile tool to improve the quality and reliability of the climate signal from tree-ring series for dendroclimatology research; and (2) time-dependent fluctuations of climate growth relationships should be taken into account when assessing the quality and reliability of reconstructed climate signals.     

Bioclimatology of beech (Fagus sylvatica L.) in the Eastern Alps: spatial and altitudinal climatic signals identified through a tree-ring network

Aim To identify the dominant spatial patterns of Fagus sylvatica radial growth in the Eastern Alps, and to understand their relationships to climate variation and bioclimatic gradients. Location Fourteen beech stands in the Eastern Alps, growing between 200 and 1500 m a.s.l. in Italy, Slovenia and Austria. Methods At each site, trees were sampled using increment borers or by taking discs from felled trees. Cores and discs were processed by measuring and crossdating ring width. Ring width series were standardized, averaged, and prewhitened to obtain site chronologies. Hierarchical Cluster Analysis (HCA) and Principal Components Analysis of prewhitened site chronologies were used to identify spatial and altitudinal growth patterns, related to the bioclimatic position of each stand. Bootstrap correlation and response functions were computed between monthly climatic variables and either principal component scores or composite chronologies from stands associated by HCA. The stability of dendroclimatic signals was analyzed by moving correlation functions (MCF). Correlation analysis (teleconnections) based on a data base of 37 Italian and Slovenian beech tree‐ring chronologies revealed the spatial extent of principal component scores. Results Sampled trees were 200–400 years old, representing the oldest beech trees that have been crossdated for the Alps to date. Maximum age was directly related to altitude and to the presence of historical forms of conservation. Tree‐ring parameters varied according to geographic patterns and the age of sampled trees. Stands were bioclimatically organized according to their location, and with reference to their elevation and distance from the Adriatic Sea. A direct response to winter temperature was found at all elevations. The altitudinal gradient ranged from low‐elevation stands, characterized by a Mediterranean‐type, late spring–summer drought signal, to mountain and high‐elevation stands, characterized by a direct response to growing season temperature plus an inverse response to the previous year’s July temperature. The mountain and high‐elevation signal was evident in Austria, the Central Alps and Slovenia, while the low‐elevation signal was confined to mountains adjacent to the Adriatic Sea. MCF revealed trends in the response to climatic factors affecting tree‐ring formation in mountain and high‐mountain stands linked to climatic warming. Main conclusions Dendroclimatic networks can be used for bioclimatic studies of tree populations. A biogeographical separation emerged between the Alps and the Apennines at the upper elevations, while different degrees of mediterraneity distinguished sites at lower elevations. This information will be useful in assessing any future climate‐related bioclimatic shifts, especially for forests at ecotones and along altitudinal gradients.     

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.     

Significant Mean and Extreme Climate Sensitivity of Norway Spruce and Silver Fir at Mid-Elevation Mesic Sites in the Alps

Climate forcing is the major abiotic driver for forest ecosystem functioning and thus significantly affects the role of forests within the global carbon cycle and related ecosystem services. Annual radial increments of trees are probably the most valuable source of information to link tree growth and climate at long-term time scales, and have been used in a wide variety of investigations worldwide. However, especially in mountainous areas, tree-ring studies have focused on extreme environments where the climate sensitivity is perhaps greatest but are necessarily a biased representation of the forests within a region. We used tree-ring analyses to study two of the most important tree species growing in the Alps: Norway spruce (Picea abies) and silver fir (Abies alba). We developed tree-ring chronologies from 13 mesic mid-elevation sites (203 trees) and then compared them to monthly temperature and precipitation data for the period 1846–1995. Correlation functions, principal component analysis and fuzzy C-means clustering were applied to 1) assess the climate/growth relationships and their stationarity and consistency over time, and 2) extract common modes of variability in the species responses to mean and extreme climate variability. Our results highlight a clear, time-stable, and species-specific response to mean climate conditions. However, during the previous-year''s growing season, which shows the strongest correlations, the primary difference between species is in their response to extreme events, not mean conditions. Mesic sites at mid-altitude are commonly underrepresented in tree-ring research; we showed that strong climatic controls of growth may exist even in those areas. Extreme climatic events may play a key role in defining the species-specific responses on climatic sensitivity and, with a global change perspective, specific divergent responses are likely to occur even where current conditions are less limited.     

The influence of the de Vries (∼ 200-year) solar cycle on climate variations: Results from the Central Asian Mountains and their global link

Long-term climatic changes related to solar forcing were examined using millennium-scale palaeoclimatic reconstructions from the Central Asian mountain region, i.e. summer temperature records for the Tien Shan mountains and precipitation records for the Tibetan Plateau. The reconstructions were based on juniper tree-ring width records, i.e. Juniperus turkestanica for the Tien Shan and Sabina przewalskii for the Tibetan Plateau. The data were processed using spectral and wavelet analysis and filtered in the frequency range related to major solar activity periodicities. The results obtained for various tree-ring chronologies indicate palaeoclimatic oscillations in the range of the de Vries (～ 210-year) solar cycles through the last millennium.The quasi-200-year variations revealed in the palaeoclimatic reconstructions correlate well (R² = 0.58–0.94) with solar activity variations (Δ¹⁴C variations). The quasi-200-year climatic variations have also been detected in climate-linked processes in Asia, Europe, North and South America, Australia, and the Arctic and Antarctica. The results obtained point to a pronounced influence of solar activity on global climatic processes.Analysis has shown that climate response to the long-term global solar forcing has a regional character. An appreciable delay in the climate response to the solar signal can occur (up to 150 years). In addition, the sign of the climate response can differ from the solar signal sign. The climate response to long-term solar activity variations (from 10s to 1000s years) manifests itself in different climatic parameters, such as temperature, precipitation and atmospheric and oceanic circulation. The climate response to the de Vries cycle has been found to occur not only during the last millennia but also in earlier epochs, up to hundreds of millions years ago.     

Climate response of cork growth in the Mediterranean oak (Quercus suber L.) woodlands of southwestern Portugal

In the Mediterranean climate regions, drought events are expected to affect the growth of forests ecosystems by changing trees growth rates and eventually inducing shifts in their growth patterns. Cork oak (Quercus suber L.) is a strictly western Mediterranean tree species periodically harvested for its bark, the cork. So far, cork oak has received limited attention for dendroclimatological studies due to its typical faint and erratic tree wood rings. Moreover, its distinct cork rings chronologies have been completely neglected. In this study we introduce an approach using cork ring chronologies dated back 9–10 years for climate response. Despite enhancing interannual variability and increasing statistical response to short-term climatic variability, still poorly understood, this study will possibly allow infer long-term climate response. We analyzed the cork ring chronologies of 55 cork samples collected in mature (under exploitation) trees in three distinct locations in southwestern Portugal. Cork growth recorded a high climate signal, with highly significant and coherent responses to the yearly climate-related sources of variation. We successfully assessed trends of cork growth via correlation analysis including selected climate variables among mean monthly temperature, monthly precipitation and, on an annual basis, eight precipitation indices. The high mean sensitivities and inter-series correlations found for cork ring chronologies combined with the significant variance explained by climate variables suggest that climate is likely one dominant signal that affects cork growth, but local environmental stresses can decisively affect this (climate) signal. Assuming cork growth as a proxy for cork oak growth, it seems conceivable that despite the trees being highly resistant to drought stress, cork oak woodlands in southwestern Portugal would have to face lesser growth in a global warming scenario.     

黄土高原健康和衰退刺槐林径向生长对气候的响应

全球气候变化导致的区域森林生长衰退和死亡普遍发生,并对森林生态系统结构和组成以及主要生态系统服务功能产生重要影响,然而相关研究在国内还显偏少。根据黄土高原延安羊圈沟小流域人工刺槐林健康和衰退个体分别构建了刺槐健康和衰退树轮年表,并对人工刺槐林健康和衰退年表特征及对气候响应敏感性进行了对比分析。结果表明刺槐衰退年表质量较低,其年表统计参量,包括平均敏感度、样芯间相关系数、信噪比和样本群体代表系数均要低于刺槐健康年表。刺槐衰退年表在生活史早期（1985-2007年）与生长健康年表的波动趋势相类似,而在生活史晚期（2008-2016年）与健康年表指数出现生长分离现象,生长速率明显偏低。年表与气候要素响应分析表明刺槐生长衰退年表对气候要素响应敏感性要低于刺槐生长健康年表,但是两者均含有干旱胁迫气候信号,主要体现在与温度呈负相关关系,与降雨和干旱指数的正相关关系。年表与极端气候年份的时序叠加分析表明,生长健康和衰退年表对极端干旱年份响应敏感性均较高,表明极端干旱胁迫条件对刺槐生长健康和衰退个体均有抑制性影响;生长健康年表对极端湿润年份响应敏感性明显高于衰退年表,表明刺槐健康个体比衰退个体更能有效利用湿润年份有利条件,而具有较高的生长速率。研究揭示出黄土高原健康和衰退刺槐个体生长趋势变化及对气候响应敏感性均存在明显差异性,将为气候变化背景下人工刺槐林生长衰退和死亡预测模型建立提供科学依据,因而对黄土高原人工刺槐林生态恢复和保护及可持续经营具有科学价值。     

Environmental heterogeneity and neighbourhood interference modulate the individual response of Juniperus thurifera tree-ring growth to climate

Individual variation of tree-ring growth response to climate and heterogeneity of the local environment are usually neglected in dendrochronological research. Even if there is evidence showing that individual responsiveness to climate may depend on intrinsic traits such as tree age, size or sex, its modulation by the local heterogeneity of extrinsic factors has been less studied. Using an extensive, strictly regular sampling scheme across a 3300 ha woodland, we assessed the individual variation of tree-ring growth responses to climate in 100 Juniperus thurifera L. trees. The climatic response was evaluated by bootstrapped correlations of both population- and individual-based tree-ring chronologies with monthly records of precipitation, cloudiness, minimum and maximum temperatures. We studied also the influence of extrinsic abiotic (elevation, slope, heat load, tree location) and biotic (competition from neighbouring trees) factors on the individual growth variation and its climatic response. At a population level, growth was controlled by February–March precipitation, April minimum temperature, and June water stress. A significant proportion of individuals did not respond to those variables, but were sensitive to others not relevant at the population level. Inter-annual growth variation was strongly modulated by competition, whereas trees under lower competition levels, in eastern and warmer areas, were the most responsive to climate. The individual climatic response was, at least partially, modulated by the local heterogeneity of extrinsic factors. By considering environmental heterogeneity and neighbourhood interference we can identify the spectrum of site-dependent climatic responses in a population, which in turn will enable more realistic predictions of tree responses to ongoing climate change.     

Removal of a non-climatically induced seven-year cycle from Nothofagus pumilio tree-ring width chronologies from Tierra del Fuego,Argentina for their use in climate reconstructions

A pronounced seven-year cycle is one of the most prominent features of many Fuegian and southern Patagonian Nothofagus pumilio tree-ring width chronologies. However, the source of this variability is still unclear. Here we provide multiple lines of evidence that suggest this phenomenon comes from non-climatically induced ecological factors, most probably triggered by insect outbreaks. To test this hypothesis we removed the seven-year cycle, by means of Singular Spectrum Analysis, from a network of 44 tree-ring width chronologies, from the eastern Tierra del Fuego Island in Argentina. The chronologies that were filtered this way showed a stronger climatic response, and were more successfully modeled using the Vaganov-Shashkin-Lite (VS-Lite) process-based forward model of tree growth. We conclude that the removed periodicity does not have a climatic source. Additional evidence from direct observation of affected and non-affected trees during defoliation, due to Ormiscodes sp. outbreak in 2010, is provided. We also tested the hypothesis of probable masting effects on the growth of N. pumilio at a site with a 12-yr record of seed production, but this hypothesis was not confirmed. Taking into account the non-climatic nature of this signal, we explore the utility of corrected chronologies for reconstruction of climatic parameters in Tierra del Fuego, especially for summer temperature and frost day frequency. This study is the first systematic analysis of the pronounced high-frequency cyclicity in N. pumilio tree growth in southernmost South America.     

长白山北坡不同年龄红松年表及其对气候的响应

运用树木年轮气候学方法,研究了长白山北坡红松(Pinus koraiensis)不同年龄年表特征及其与气候因子间的关系,以期揭示年龄因素对年表的潜在影响。结果表明,平均年龄为63a的红松低龄年表与平均年龄为184a的高龄年表对气候的响应明显不同:低龄红松径向生长与当年1、2月月平均温度负相关(P<0.05),同时也受到上年及当年多个月份的月平均最高温度或最低温度的影响,但与降水的相关性未达到显著水平;高龄红松径向生长则与月平均温度间的关系不明显,而与当年1、2、4、6、7、9月的月平均最高温度正相关,与当年4月、9月的月平均最低温度负相关,同时受到上年5月及当年5月月总降水量的影响。因此,年龄因素对红松年表的气候响应方面存在一定影响,且高龄年表对气候响应的敏感性更高,包含有更多的气候信息。     

江西大岗山地区7-9月降水量的重建与分析

根据江西大岗山地区4个采样点的马尾松年轮样本,建立了本地区的综合年轮年表,分析了马尾松径向生长与气候因子变化的相关及响应关系,发现大岗山地区树木径向生长受生长季7—9月降水量影响较显著,呈负相关关系。在响应分析的基础上,首次重建了大岗山地区1892年以来7—9月的降水量,交叉检验表明重建序列是可靠的。重建结果表明,大岗山地区7—9月份降水变化在过去的117年中总体经历了3个偏干时期：1895—1902年,1908—1926年和1944—1985年,和3个偏湿阶段：1903—1907年,1927—1943年及1986—2008年。重建的降水量序列在1921年,1937年及1977年发生明显的方差突变,表明百年以来该地区降水量变化趋势存在阶段性变化。     

Vessel features of Quercus ilex L. growing under Mediterranean climate have a better climatic signal than tree-ring width

We investigated whether vessel time series of Holm oak (Quercus ilex L.), a diffuse to semi-ring-porous species, can record a climatic signal which differs from the signal encoded in tree-ring width (TRW). The study was conducted in ten Q. ilex trees from a coppice stand in northeast Spain. Chronologies of TRW, mean vessel area (MVA) and maximum vessel area (MAX) were developed and correlated with climate data, for the period 1985–2004 (20 years). Our results indicate that vessel features contain environmental information that is different from that stored in TRW. MAX chronologies correlate better to early spring precipitation (April–May) than TRW chronologies, and so does MVA of the largest 20–25 vessels from the first third of the ring with late spring precipitation (May–June). Also, the combination of MVA and TRW is a better predictor of summer precipitation. This explorative study clearly shows that vessel features can complement the climatic signal of TRW increasing the resolution of the climate reconstructions for the Mediterranean region.