No description available.

Tree-ring samples were collected from six coniferous species in the western Himalayan ranges during the summer of 1984 in order to evaluate their potential for use in dendroclimatic reconstructions. Picea, Abies, and Pinus spp. had previously been collected for ring widths and densitometric analysis by Hughes and co-workers on relatively mesic subalpine sites near the Vale of Kashmir. Our results support this earlier work in that ring-width series from these habitats are relatively complacent and contain little dendroclimatic information. Density and ring widths are largely temperature-dependent. However, our sampling included Cedrus deodara and Pinus gerardiana from lower altitudes in the dry inner valleys of the Pir Panjal Range, south of Kashmir. Both species exhibit great age, high mean sensitivity and good intra- and inter-specific crossdating, and yielded chronology statistics suggestive of a drought response. We strongly recommend that they receive high priority in future tree-ring research in northwest India.

The first dendrochronolcgical investigation in the USSR was carried out at the end of the past century. Systematic study of tree rings for the purpose of dating different events and reconstruction of natural conditions began in 1950-1960's. Tree-ring analysis is most intensively used in the studies of forest ecosystem dynamics, timing and frequency assessment of catastrophic phenomena, reconstruction of radiocarbon content in the Earth atmosphere, and dating of historical wood. Much attention is given to the development of long-term prognoses of tree growth and forest environments.

No description available.

Two modem tree-ring width chronologies of Pinus sylvestris L. have been established in an area near the southern limit of the species' distribution. Trees were sampled in the South of Catalonia in northeastern Spain where Mediterranean climatic conditions are of primary influence. To better understand climate ring-width relationships, tree-ring index series have been studied in relation to local climate. Ring-widths are strongly related to low precipitation at the beginning of the growing season in March, in June of the current growth year, and in September prior to tree-ring growth. High temperatures mainly affect growth in summer during the growing season and in autumn of the year prior to growth. During the winter, mainly in December, mean monthly temperatures show a significant positive correlation with growth. Major factors controlling the southern distribution of P. sylvestris may be related not only to water stress in summer but also to the amount of precipitation at the beginning of the growing season and in autumn, even in mild winters.

Thirty-one old-age pine stands in nine mountainous regions of Spain were studied in order to delineate dendrochronologically uniform areas. A country-wide cross-correlation analysis of the autoregressively standardized site chronologies showed the dendrochronological signal decreasing with distance so that beyond about 450 km crossdating becomes less reliable, but even over 630 km, the correlation coefficient is sometimes significantly high. A principal components analysis of the variance among the site chronologies segregated the chronologies into a northern and a southern group roughly along a line from Madrid to Barcelona. Two low-elevation northern sites were grouped with the southern sites. Moisture supply limits the growth of the pines in this group. In contrast, the high-elevation northern sites do not suffer from prolonged droughts. According to the uniform and extensive tree-ring signal in the south of the peninsula, the potential of dendrochronology for dating cultural objects is predicted to be favorable. Because of the greater variability between sites in the north, further studies are necessary to delineate uniform areas.

Twenty-three Libocedrus bidwillii (New Zealand cedar) tree-ring chronologies have been developed from New Zealand. This total consists of twelve new sites collected by the authors and eleven previously collected by others (five of which we have updated and six of which were not). Standardization of the tree-ring series from each site used a double detrending method (linear-exponential or linear regression or a horizontal detrending plus spline detrending fitted to 2/3 the length of each tree-ring series). ARSTAN modeling using the Aikaike Information Criterion (AIC) to determine the filter model removed all significant autocorrelations from the residual chronologies. The average chronology length is around 500 years, and the sites are spread over 8° of latitude (i.e.. 38°-46 °S) and nearly 10(X) m in elevation (i.e., 244-1220 m.a.s.1.). The species tends to grow slowly (mean ring-width 0.7 mm), and the tree rings have a high autocorrelation value (0.79). The average mean sensitivity was 0.17, and the average mean correlation between all radii within chronologies was 0.55. Comparison of the chronologies showed a highly consistent and significant pattern among most of the sites. There was a reduction in interchronology correlation with separation distance; however, there was no clear relationship, or an effect, due to elevation. The spatial extent and temporal length of the network of sites offers the most comprehensive opportunity for New Zealand climate reconstruction to date.

To determine the response of tree rings to climate, twenty cores were extracted from ten trees of Pinus pinea L. in Istanbul-Alemdag. A response function was used to characterize the relationships between tree rings and temperature and precipitation. The precipitation of the current year and the temperature at the beginning of the growing period have a significantly positive influence on the growth of the tree ring. Mean sensitivity was found to be 0.291, and it was concluded that Pinus pinea L. is a dendroclimatologically sensitive species.

Progressive tree-ring xylem cell size changes may reveal the influence of changing environment during the growing season. This study examines xylem tracheid cell growth in red pine (Pious resinosa Ait.) seedlings grown in cabinets under controlled environment, where single parameters (temperature, light, soil moisture and CO2) were varied step-wise in each chamber at ca. 30-day increments for ca. 6 months. Control and temperature treatments were replicated. Cross-sections (20 μm thick) sliced with a sliding microtome from each of four seedling stems from each cabinet were mounted on glass slides. Lumen diameters and cell-wall thickness were measured on 4 orthogonal tracheid radial files on 4 radii of each stem. Mean cell sizes were 11-17 μm among treatments and growth periods, whereas numbers of cells formed averaged 0.2-1.3 cells per day. Cell size increased throughout the experiment in most of the treatments, including one of the control treatments and those with the greatest potential to limit growth (decreasing temperature, light and soil moisture). Soil moisture was the only environmental parameter that tended to cause late declining growth, and CO, up to 500 (μmol mol⁻¹ did not appear to influence cell development. Despite a substantial range of environmental shifts in the chambers (100 μmol mol⁻¹ CO₂; 125 μEinsteins m⁻² s⁻¹ light; 8 °C temperature; 35% relative humidity; watering every day to every 5th day), the continued stem elongation and cell-size increases indicate that conditions never became significantly limiting to growth in most treatments. Although the range of environmental variability is undoubtedly much greater in most natural red pine systems, these results indicate that fairly large variations in environment during development of juvenile wood in seedlings may not leave an imprint retrievable from cell-size measurements made on the earliest rings of mature trees.

The objective of this study was to document correlations between radial growth of white oak (Quercus alba L.) at 128 sites in the eastern US and variables related to early growing season site water balance, including the ratio of actual to potential evapotranspiration (AE/PE) computed based on the procedure described by Thornthwaite and Mather (1957). White oak radial growth was strongly correlated with all measures of early growing season water balance, but was most consistently and strongly correlated with Palmer Drought Severity Index (PDI) and AE /PE ratio computed using a modified Thornthwaite-Mather model. We propose that dendroecological analyses of tree growth responses to climate based on AE /PE variables could provide empirical data useful for improving climate response algorithms in forest simulation models. This change of standard practice could also improve biological interpretations derived from such dendroecological analyses.