Ring-width Variations Research Articles

Relationship between Ring Width and Tracheid Characteristics In Picea crassifolia: Implication in Dendroclimatology

Ring width represents the total width of cells in a growing season. Relatively few studies have identified which of the parameters, cell number, size, or wall thickness is the greater contributor to variations in ring width. It is difficult to clearly explain the relationship between the climate in which a tree is located and the ring growth. In this study, the ring width and various tracheid characteristics (radial lumen diameter, double wall thickness, and number) in 298 rings of Picea crassifolia wood were investigated. Tree rings were quantitatively categorized based on their width into large, medium, and narrow classes. The tracheid number and lumen diameter were strongly correlated with annual ring width. The tracheid number had the strongest effect on the ring width. The effect of the tracheid number was three times larger than that of the lumen diameter. More earlywood cells were formed in larger rings, while larger earlywood cells were produced in years when narrow rings were formed. Wall thickness had no appreciable effect on ring width. The results of this study help to understand the relationship between the climate and the ring growth from the tree physiology perspective, when ring width is used as a climate proxy.

Modeling regional and climatic variation of wood density and ring width in intensively managed Douglas-fir

Characteristics of annual rings are reliable indicators of growth and wood quality in trees. The main objective of our study was to model the variation in annual ring attributes due to intensive silviculture and inherent regional differences in climate and site across a wide geographic range of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Ring specific gravity and ring width of Douglas-fir were examined at five long-term Levels-Of-Growing-Stock (LOGS) installations, three in the US and two in Canada, covering a latitudinal gradient between 43°N and 50°N. At each location, increment cores were collected from replicated plots with three levels of stocking: control (unthinned), lightly thinned (70% basal area retention), and heavily thinned (30% basal area retention). X-ray densitometry analysis provided ring specific gravity and width profiles for 5676 rings from 134 trees. The reduction of stand density through repeated entries resulted in decreased ring specific gravity and increased ring width. A four-parameter mixed-effects logistic model was used to predict ring specific gravity using cambial age, stand density (as number of stems per hectare), and two climatic variables: average temperature from March to May and total precipitation from April to August. A three-parameter mixed-effects logistic model was used to predict ring width using cambial age, stand density (as stand density index), and total climatic moisture deficit of June and July. Both models indicated significant site differences that were included in the models through indicator variables. Ring specific gravity increased slightly with increasing average temperature from March to May and decreasing total precipitation from April to August. Predictions of ring specific gravity of Douglas-fir appear to be more sensitive to changes in temperature compared with changes in precipitation.

长白山不同海拔树木生长对气候变化的响应差异

Trees growing at the margins of their species' distributional ranges are considered to be the most sensitive to environmental factors. In tree species distributed across wide elevational gradients and playing vital roles in local ecosystems,altitudinal variation in growth conditions may be of great importance for sustainable forest management. The importance of altitudinal gradients is thus often emphasized. To investigate climate-growth relationships at different elevations,tree-ring width chronologies of Larix olgensis and Pinus koraiensis were developed from four and six sampling sites,respectively,at different elevations of a north-facing slope in the Changbai Mountains of northeastern China. Ten final residual chronologies were produced. Mean sensitivity( MS) and standard deviation( SD) were used to describe interannual variability in ring width as a proportion of local mean ring width. The signal-to-noise ratio( SNR) served as an expression of the strength of the observed common signal among trees. All chronologies had relatively high MS,SD,and SNR values, which reflected the sensitivities of trees to environmental conditions. There were no consistent trends in statistical characteristics of tree-ring chronologies along the elevational gradient. For L. olgensis,all values decreased with increasing elevation,reaching a minimum at the mid-elevation site; increases in these values were then observed above the midelevation site,which suggested that trees in the mid-elevation site had a complacent growth pattern. For P. koraiensis,all values increased with increasing elevation,reaching a maximum at the mid-elevation site,and then decreasing. Hierarchicalclustering analysis was used to highlight differences in radial growth among sites and to determine radial growth associations. For L. olgensis,chronologies were classified into two groups—low and high elevation—,while P. koraiensis chronologies at large were categorized into three groups—low,intermediate,and high elevation. Correlation and response functions were analyzed to determine primary climatic influences on growth. The bootstrap method was used to test significance. Monthly mean temperature and monthly total precipitation were used for the analysis. Our results suggest that along the elevational gradient,both species may respond in different ways to local climate change. March and June temperatures and previous November temperatures appeared to be the primary limitations to L. olgensis growth under either high or low elevation chronologies. Our data demonstrate that temperature is the dominant factor limiting growth at high elevations. At low elevations,no significant correlations with the current year' s climatic conditions were discerned. The previous year' s October temperatures and June precipitation affected P. koraiensis at high elevations. This lag in response suggests that a relatively warm autumn may favor the following year's growth. Precipitation in the previous year,temperature of the current year,and current spring temperatures had the greatest contributions to P. koraiensis growth at either intermediate or low elevations. In both species,lag effects were observed in growth responses to climate forces. Comparing the two species,L. olgensis is cold-tolerant,whereas P. koraiensis is warm-loving. The elevational differences in responses of L. olgensis and P. koraiensis to climate that were uncovered in this study should assist future regional dendroclimatological studies.

Disturbance legacies and climate jointly drive tree growth and mortality in an intensively studied boreal forest

Most North American forests are at some stage of post-disturbance regrowth, subject to a changing climate, and exhibit growth and mortality patterns that may not be closely coupled to annual environmental conditions. Distinguishing the possibly interacting effects of these processes is necessary to put short-term studies in a longer term context, and particularly important for the carbon-dense, fire-prone boreal forest. The goals of this study were to combine dendrochronological sampling, inventory records, and machine-learning algorithms to understand how tree growth and death have changed at one highly studied site (Northern Old Black Spruce, NOBS) in the central Canadian boreal forest. Over the 1999-2012 inventory period, mean tree diameter increased even as stand density and basal area declined significantly. Tree mortality averaged 1.4 ± 0.6% yr-(1), with most mortality occurring in medium-sized trees; new recruitment was minimal. There have been at least two, and probably three, significant influxes of new trees since stand initiation, but none in recent decades. A combined tree ring chronology constructed from sampling in 2001, 2004, and 2012 showed several periods of extreme growth depression, with increased mortality lagging depressed growth by ~5 years. Higher minimum and maximum air temperatures exerted a negative influence on tree growth, while precipitation and climate moisture index had a positive effect; both current- and previous-year data exerted significant effects. Models based on these variables explained 23-44% of the ring-width variability. We suggest that past climate extremes led to significant mortality still visible in the current forest structure, with decadal dynamics superimposed on slower patterns of fire and succession. These results have significant implications for our understanding of previous work at NOBS, the carbon sequestration capability of old-growth stands in a disturbance-prone landscape, and the sustainable management of regional forests in a changing climate.

Variation in wood density and ring width in Acacia melanoxylon at four sites in Portugal

The radial variation in wood density in Acacia melanoxylon R. Br. was studied using microdensitometry by sampling 20 trees with a 40-cm diameter class at four sites in Portugal. The measurements were taken from pith to bark at breast height. A. melanoxylon had an average ring density of 0.607 g cm−3, ranging from 0.556 to 0.630 g cm−3. The mean growth was 6.0 mm year−1. Latewood corresponded, on average, to 34 % of the ring width. Between-tree variability at each site was the main source of variation in the density components, representing between 30 and 54 % of the total variation. Between-sites variability represented from 0 to 21 % of the total variation in density components. The environmental effects (site related) were more pronounced on latewood, while the genetic effect (tree related) was more evident in earlywood. Ring width, latewood percentage and heterogeneity index were independent from site, trees in site and age effects. The values of wood density and radial growth revealed that A. melanoxylon can be important as a commercial timber species in Portugal.

Climate Control on Tree Growth at the Upper and Lower Treelines: A Case Study in the Qilian Mountains, Tibetan Plateau

It is generally hypothesized that tree growth at the upper treeline is normally controlled by temperature while that at the lower treeline is precipitation limited. However, uniform patterns of inter-annual ring-width variations along altitudinal gradients are also observed in some situations. How changing elevation influences tree growth in the cold and arid Qilian Mountains, on the northeastern Tibetan Plateau, is of considerable interest because of the sensitivity of the region’s local climate to different atmospheric circulation patterns. Here, a network of four Qilian juniper (Sabina przewalskii Kom.) ring-width chronologies was developed from trees distributed on a typical mountain slope at elevations ranging from 3000 to 3520 m above sea level (a.s.l.). The statistical characteristics of the four tree-ring chronologies show no significant correlation with increasing elevation. All the sampled tree growth was controlled by a common climatic signal (local precipitation) across the investigated altitudinal gradient (520 m). During the common reliable period, covering the past 450 years, the four chronologies have exhibited coherent growth patterns in both the high- and low-frequency domains. These results contradict the notion of contrasting climate growth controls at higher and lower elevations, and specifically the assumption that inter-annual tree-growth variability is controlled by temperature at the upper treeline. It should be stressed that these results relate to the relatively arid conditions at the sampling sites in the Qilian Mountains.

An evaluation of wood properties of <i>Pinus caribeae</i> (Morelet) in Oluwa Forest Reserve, Ondo State, Nigeria

This paper examines the effects of within tree variation on wood density, ring width and anisotropic shrinkage of Pinus caribeae (Morelet) among tree partitions in Oluwa pine plantation. Five 15-year old Pinus caribeae (Morelet) in three partitions were randomly selected from the plantation and felled for the study. Wood samples were prepared from five height levels, 10%, 30%, 50%, 70% and 90% and also among the wood type; inner wood, middle wood and outer wood positions of the stem according to standard procedures. The result showed the wood is dense, dimensionally stable with an average density of 0.55g/cm3. Among three partitions, ring width variation had a marked effect on wood density and anisotropic shrinkage of the wood (p < 0.05). A strong positive correlation was established between density and shrinkage properties. The relationship between ring width and anisotropic shrinkage was positive. Thus, it may be possible to use wood density and grain orientation biometry to predict anisotropic shrinkage of the wood and its dimensional stability.Key words: Density, Ring width, anisotropic shrinkage, Pinus caribeae (Morelet)

Effect of ring width, cambial age, and climatic variables on the within-ring wood density profile of Norway spruce Picea abies (L.) Karst.

Studying the effects of dendrometric and climatic variables on within-ring density variations needs flexible and interpretable models. We described the within-ring density profile using a piecewise linear regression and studied its dependence on (1) dendrometric variables such as cambial age (CA) and ring width (RW), and (2) climatic variables. Based on X-ray analysis of 5,191 Norway spruce rings, a six-parameter three-segmented model was fitted on each within-ring density profile. Each model parameter was related to dendrometric and climatic variables using multiple linear regressions. Then, these models were assembled in two models relating the within-ring density profile to (1) RW and CA (model M1), and (2) climatic variables (model M2). M1 showed an R 2 of 83.4 % and a residual standard error of 68.5 kg m−3. Larger rings were associated with a decrease of latewood proportion and mean ring density. Rings with high CA were characterised by high maximum ring density. M2 showed an R 2 of 60.9 % and a residual standard error of 94.9 kg m−3. Warm summers increased the maximum ring density. Years with favourable water status decreased mean ring density. The piecewise linear models allowed the classification of within-ring density profiles in three types. Considering CA and RW led to the most explicative model since RW described many processes such as silviculture or climate. Earlywood density was impacted by water status while latewood density was conditioned by both temperatures and water status. Our approach may be used for the identification of within-ring density fluctuations or to assess the effects of silviculture or global change on the within-ring density profile.

Climatic control of tracheid production of black spruce in dense mesic stands of eastern Canada

Inferences on climate change effects are reliable only if they are based on a causal relationship rather than simple statistical predictive capacity. To assess for causal links between climate and mature black spruce (Picea mariana (Mills.) BSP) radial growth, we combined the use of wood anatomy, cambium phenology, climate and soil measurements (air temperature and humidity, precipitations, soil temperature and water content, photosynthetically active radiation), and a model selection approach proceeding backwards from a full model. Results show that the number of tracheids is responsible for 88% of the variation in ring width whereas mean tracheid diameter accounts for the remaining 12%. The number of tracheids produced depends on factors related to photosynthesis during tracheid production, i.e., daily light intensity and maximum temperature between the day of initiation and the day of cessation of tracheid production, plus soil temperature during August of the previous year which is an important period for determining the number of new needles produced. It is also important to consider duration of the period for tracheid production. These results imply that short-term climate change should increase black spruce radial growth. They also suggest that the typical use of post-growth ring width sampling individually linked to air temperature and precipitations is not sufficient to infer climate change effects accurately on radial growth where there is no strong single climatic limitation but multiple limitations instead.

Preliminary dendrochronological studies on Populus euphratica in the lower reaches of the Heihe River basin in northwest China

To date, preliminary dendrochronological studies of Euphrates poplar trees have not been reported, even though some dendrohydrological studies have been performed. Based on 11 sites in the Ejin Oasis, located in the lower reaches of the Heihe River basin in northwest China, our studies of Euphrates poplar trees concentrates on the characteristics of the tree-ring structure and the stem radial growth, which is the foundation of accurate crossdating and detrending. The results indicate that the Euphrates poplar trees studied have identifiable ring boundaries; the narrow rings and the same ring width variation pattern make the crossdating achievable. The local habitat, the stem radial growth trend of the poplar trees and the completeness of cores should be valued when selecting a detrending method. The complex ring width variation pattern of the poplar trees in the area suggest that comprehensive sampling and preliminary dendrochronological studies are required to gain insights into the spatiotemporal growth patterns of the poplar trees and their relationship with the changing water environment.

Wood density variations of Norway spruce (Picea abies (L.) Karst.) under contrasting climate conditions in southwestern Germany.

We analyzed inter-annual variations in ring width and maximum wood density of Norway spruce ( Picea abies (L.) Karst.) at different altitudes in Baden-Wurttemberg, southwestern Germany, to determine the climate response of these parameters under contrasting climate conditions. In addition, we compared maximum, average and minimum wood density between sites. Bootstrapped correlation coefficients of ring width and maximum wood density with monthly temperature and precipitation, revealed a different climate sensitivity of both parameters. Ring width showed strong correlations with climate variables in the previous year and in the first half of the growing season. Further, a negative relationship with summer temperature was observed at the low-altitude sites. Maximum wood density correlated best with temperature during the growing season, whereby strongest correlations were found between September temperature and maximum wood density at the high-altitude sites. Observed differences in maximum, average and minimum wood density are suggested to relate to the local climate; with lower temperatures and higher water availability having a negative effect on wood density.

Growth rate and ring width variability of teak, <i>Tectona grandis</i> (Verbenaceae) in an unmanaged forest in East Timor.

Teak (Tectona grandis) is one of the most valuable timbers in international trade and an important species for tropical forestry. Teak is found on the island of East Timor but no information is available on teak growth from this region. A pure stand planted in 1940-50 in the North of East Timor and left unmanaged was studied. Fifteen trees were sampled in October-November 2003 and stem discs taken at three height levels of its height (1.7m, 9.5m and 18.7m), and cores were collected at DBH. Transverse surfaces of the discs and cores were polished for ring identification. Core cross sections were first digitized and disc cross sections were observed under the microscope. Three randomly selected radii were analyzed in each disc. Ring width measurement and ring counting were done using image analysis software. The distinction between heartwood and sapwood was performed macroscopically by colour difference, and heartwood radius and sapwood width were measured. The relationship between stem and heartwood radius was studied for each disc and heartwood percentage by radius was determined. Radial ring width curves are presented for the different axial positions within the stem, and ring width variability was analyzed. Growth rates were calculated and age-radius relationships were estimated using cumulative growth curves. Growth rings were large and well defined in the juvenile phase, reflecting the specie's fast-growing character. The year-to-year variation of ring width showed a similar pattern among trees. Mean ring width ranged between 4.3-7.3mm for the first 20 years and 3.3-5.1mm for 30 to 45 years. Pith eccentricity was evident in the lower part of the stem and ring wedging occurred. On average, heartwood represented 84% of the radius and sapwood contained 6 to 11 rings. The age-related variation of ring width and the occurrence in the lower part of the tree stems of eccentricity and wedging rings, highlights the importance of appropriate stand management, particularly regarding basal density distribution over time, whenever optimized timber production is envisaged.

Secular temperature trends for the southern Rocky Mountains over the last five centuries

Pre‐instrumental surface temperature variability in the Southwestern United States has traditionally been reconstructed using variations in the annual ring widths of high altitude trees that live near a growth‐limiting isotherm. A number of studies have suggested that the response of some trees to temperature variations is non‐stationary, warranting the development of alternative approaches towards reconstructing past regional temperature variability. Here we present a five‐century temperature reconstruction for a high‐altitude site in the Rocky Mountains derived from the oxygen isotopic composition of cellulose (δ18Oc) from Bristlecone Pine trees. The record is independent of the co‐located growth‐based reconstruction while providing the same temporal resolution and absolute age constraints. The empirical correlation betweenδ18Ocand instrumental temperatures is used to produce a temperature transfer function. A forward‐model for cellulose isotope variations, driven by meteorological data and output from an isotope‐enabled General Circulation Model, is used to evaluate the processes that propagate the temperature signal to the proxy. The cellulose record documents persistent multidecadal variations inδ18Octhat are attributable to temperature shifts on the order of 1°C but no sustained monotonic rise in temperature or a step‐like increase since the late 19th century. The isotope‐based temperature history is consistent with both regional wood density‐based temperature estimates and some sparse early instrumental records.

Influence of drought on tree rings and tracheid features of Pinus nigra and Pinus sylvestris in a mesic Mediterranean forest

We investigated the influence of climate on the ring width and xylem anatomy of two co-occurring pines (Pinus nigra Arn. and P. sylvestris L.) in the mountains of east-central Spain in order to test their utility for dendroclimatic reconstructions. We developed chronologies of ring width, mean lumen diameter and mean cell-wall thickness (in the earlywood, latewood, and the total annual ring) and the number of cells between 1960 and 2006. Drought, expressed as the standardized precipitation-evapotranspiration index (SPEI), was the main climatic driver of tree radial growth, although trees were also sensitive to temperature (negative effect in previous autumn and current summer) and precipitation (with a general positive effect). P. sylvestris response was stronger to climate of the current year, whereas the effect of previous-year climate was more important for P. nigra. Warm and dry summers reduced ring width, tracheid lumen, and wall thickness in both species, whereas warm winter-spring temperatures had the opposite effect, primarily for P. sylvestris. Previous-year or early-season conditions mainly affected earlywood features, whereas latewood was more responsive to summer climate. Overall, climate appeared to be a stronger limiting factor for P. sylvestris. During periods of drought, cell-wall thickness was reduced while lumen width increased in the latewood of P. sylvestris. This could compromise its hydraulic safety against drought-induced cavitation as our site was close to the southern and dry edge of the species distribution area. Our results suggest that anatomical variables record different and stronger climate information than ring width variables, especially in P. sylvestris. Reconstruction models for SPEI at the 3-month scale were developed for July–August and September–October using principal components regression. The best models included anatomical and width variables of both pine species suggesting that tracheid chronologies can be useful for drought reconstructions especially at mesic sites or with species that encode a mixed drought and temperature-precipitation signal.

Ensemble estimates reveal a complex hydroclimatic sensitivity of pine growth at Carpathian cliff sites

Carpathian pine growth at its natural range limit, where small hydroclimatic fluctuations are indicated by tree-ring width anomalies, may provide insight into past ecological responses to climatic changes. Tree-ring chronologies from extreme cliff sites may also contain annually resolved and accurately dated information to facilitate the development of palaeoclimatic reconstructions. Complex and spatiotemporally inconsistent relationships between biotic and abiotic factors, however, often complicate our understanding of forest growth dynamics. In this study, we utilized a novel ensemble approach of 3240 growth–climate interactions to evaluate the likelihood of temporal fluctuations in the hydroclimatic sensitivity of three newly developed tree-ring width chronologies from 515 Scots pines (Pinus sylvestris). The data represent undisturbed cliff habitats across the northwestern Carpathian arc between 700 and 1050m asl. These sites are located in the northern (N) and southern (S) Tatra Mountains and in-between (M). Two sites (N, S) share common interannual to multi-decadal ring width variability (r=0.73), and they significantly capture variations in 20th-century summer drought conditions (r=0.52–0.65). Temporal instability in the growth–climate response, however, occurred in all three tree-ring chronologies, thus challenging any possible palaeoclimatic value. Orographic-induced climatology was found to dominate the observed growth–climate inconsistency, whereas age-related physiological mechanisms and differences in the absolute growth levels of the trees, as well as methodological standardization constraints and seasonal climate differences appeared to be less important. Our results suggest that environmental and ecological site criteria should be routinely supplemented by statistical data assessments prior to employing tree-ring chronologies for climate reconstructions.

Process based model sheds light on climate sensitivity of Mediterranean tree-ring width

Abstract. We use the process-based VS (Vaganov-Shashkin) model to investigate whether a regional Pinus halepensis tree-ring chronology from Tunisia can be simulated as a function of climate alone by employing a biological model linking day length and daily temperature and precipitation (AD 1959–2004) from a climate station to ring-width variations. We check performance of the model on independent data by a validation exercise in which the model's parameters are tuned using data for 1982–2004 and the model is applied to generate tree-ring indices for 1959–1981. The validation exercise yields a highly significant positive correlation between the residual chronology and estimated growth curve (r=0.76 p<0.0001, n=23). The model shows that the average duration of the growing season is 191 days, with considerable variation from year to year. On average, soil moisture limits tree-ring growth for 128 days and temperature for 63 days. Model results depend on chosen values of parameters, in particular a parameter specifying a balance ratio between soil moisture and precipitation. Future work in the Mediterranean region should include multi-year natural experiments to verify patterns of cambial-growth variation suggested by the VS model.

Do High-Elevation Northern Red Oak Tree-Rings Share a Common Climate-Driven Growth Signal?

Six open-canopy high-elevation northern red oak (Quercus rubra L.) ring-width records were evaluated along the Southern Appalachian mountain range for a common climate-driven growth signal. Ring-width records show significant correlations over the past two centuries with principal component one (PC-1) accounting for 50% of the common variance. Spectral analysis reveals that the relative variance in ring-width is concentrated at decadal time scales. Ring-width records show positive correlations (p < 0.05) with prior fall–early winter and current summer mean temperature, and negative correlations (p < 0.05) with prior late summer–winter total precipitation. Yet, temperature-precipitation covariance along the Southern Appalachian mountain range during winter and summer seasons undergoes a significant reversal with intervening spring and fall seasons showing weak association. As a result, ring-width-climate signal strength exhibits time-dependence over the instrumental period, although the temporal change is not statistically significant. This temporal change suggests that both temperature and precipitation can have a marked influence on ring-width variability depending on the degree of seasonal covariance. Finally, obtaining a stable interannual climate-growth calibration for these particular ring-width records remains a foremost challenge, and is a primary consequence of mixed temperature-precipitation signal strength and little power at higher frequencies.

Reconstructed temperature for Yong'an, Fujian, Southeast China: Linkages to the Pacific Ocean climate variability

Variations in ring width of Pinus massoniana were used to develop high-resolution climate proxy data to extend the existing climate record in Yong'an, Fujian Province, Southeast China. Growth–climate response analyses showed that the total ring width (TRW) in the subtropical zone of Fujian Province is mainly influenced by summer–autumn temperature variability. Based on the total ring width chronology derived from one chronology site (LBY), we developed July–October minimum temperature reconstruction for the period A.D. 1803–2008. The climate/tree-growth model accounts for 42.2% of the instrumental temperature variance during the period 1954–2008. Warm periods occurred during 1808–1815, 1833–1853, 1862–1871, 1895–1906, 1914–1927 and 1973–present; while the periods of 1803–1807, 1816–1832, 1854–1861, 1872–1894, 1907–1913 and 1928–1972 were relatively cold. There is a reasonable agreement with the cold and warcum periods previously estimated from tree-rings around Western Pacific Ocean. The climate correlation analyses with summer APO and gridded climate dataset revealed that our season temperature reconstruction contains the strong climate signals for Asian-Pacific.

Cellulose microfibril angle variation in Picea crassifolia tree rings improves climate signals on the Tibetan plateau

Microfibril angle (MFA) is an important factor in determining the mechanical properties of individual cells and wood as a whole. While some studies have described the variation of MFA within trees, little work has been done on the extent to which MFA is influenced by climate, despite it being known to respond to climatic events. Year-to-year variation in MFA and ring width was measured at high resolution by SilviScan-3® on 30 dated Piceacrassifolia trees growing in the northeastern Tibetan plateau. The climate signals registered in MFA and ring width were analyzed using dendroclimatological methods. The response function of MFA accounted for 67% of total variance, of which 60% was explained by climate elements. The response function of ring width explained 57% total variance, 37% of which was explained by climate variables. MFA significantly responded to July–August temperatures, and to precipitation in March, May and September. Over the period 1987–2009 temperatures generally increase and appeared to have a greater influence on MFA. A decrease in the strength of the relationship between MFA and ring width over the period 1987–2009 was also observed. MFA offers the potential to build robust climate proxies. The strong climate sensitivity of MFA to increasing temperature or the observed changes in the MFA–ring width relationship may contribute to resolving the “divergence problem” in temperature reconstructions. As far as we are aware, this study is the first to show a strong climate response in MFA and suggests that it might be a useful climate proxy.

Sensitivity of Beech Trees to Global Environmental Changes at Most North-Eastern Latitude of Their Occurrence in Europe

The present study aimed to detect sensitivity of beech trees (Fagus sylvatica L.) to meteorological parameters and air pollution by acidifying species as well as to surface ozone outside their north-eastern distribution range. Data set since 1981 of Preila EMEP station enabled to establish that hot Summers, cold dormant, and dry and cold first-half of vegetation periods resulted in beech tree growth reduction. These meteorological parameters explained 57% variation in beech tree ring widths. Acidifying species had no significant effect on beech tree growth. Only ozone was among key factors contributing to beech stand productivity. Phytotoxic effect of this pollutant increased explanation rate of beech tree ring variation by 18%, that is, up to 75%. However, due to climate changes the warmer dormant periods alone are not the basis ensuring favourable conditions for beech tree growth. Increase in air temperature in June-August and decrease in precipitation amount in the first half of vegetation period should result in beech tree radial increment reduction. Despite the fact that phytotoxic effect of surface ozone should not increase due to stabilization in its concentration, it is rather problematic to expect better environmental conditions for beech tree growth at northern latitude of their pervasion.