A general discussion regarding problems inherent to developing climatically sensitive tree-ring chronologies from eastern North America is presented. Tree-ring collections from eastern forests are typically not as climatically sensitive as western collections. Collections have been made from a diversity of sites, but it seems that collections from wet sites or sites of extremely shallow soils may have limited potential. The detrimental effect of crown crowding on sensitivity suggests preference be given to shade-tolerant species and to trees with less crowded crowns exposed in the canopy. Nonclimatic trends in tree-ring data are classified as growth trends and competition trends. Standardization of ring widths removes much of the growth trends, and merging individual tree chronologies into a mean collection chronology eliminates much of the competition trends of individual trees. Separation of ring width into earlywood and latewood widths, where possible, may be quite beneficial for non-pored and diffuse-porous species. However, this procedure seems to be of little value for ring-porous species.

No description available.

An original procedure and a new mathematical technique have been developed which allowed us to obtain more reliable climatic reconstructions than with prior methods. They have been tested for different sites in Switzerland and Morocco. First, cores that were too short and cores that were not coherent enough with others were excluded, using cross-spectral analysis. Second, detrending and master chronologies were calculated. Three methods were compared: polynomial, high-pass filter, and spline indexing. An optimal detrending was obtained through comparison with climate, but there seems to be no general rule for it. More reliable and longer climatic reconstructions are made possible. A response functions technique in three steps is presented: regression after extracting principal components on monthly climatic parameters, on seasonal parameters, and on more biological parameters such as potential evapotranspiration, multiple spectral regression introducing frequency domain. This procedure provides a more complete and more dynamic view of tree growth. The transfer function method and its verification are illustrated for different sites in Morocco: three climatic parameters in Tetouan (February, May, and June temperatures) and one in Marrakech (May temperature) have been successfully reconstructed. These reconstructions are confirmed by different verifications.

Because of the propensity of cypress trees (Taxodium distichum) to form false or incomplete annual rings, the use of their growth rings for impact analysis is limited. However, the error associated with reading growth rings can be estimated by comparing two cores from the same tree, and the error inherent in a single core can be reduced by averaging the growth estimate over 6-10 years.

No description available.

Dendrochronological sampling of sixteen stands of kauri (Agathis australis) covering almost the whole range of the species in northern New Zealand is described. Eight new chronologies were obtained and compared to previous results from the same species. It is concluded that north-facing slopes are most suitable for tree-ring studies in this species. The chronologies cover a maximum period from A.D. 1580 to 1981 and show from 20 to 35 percent common chronology variance over the sample period 1790 to 1976. All the chronologies are significantly correlated with all others, and the degree of correlation appears unrelated to the spatial separation between the sites. Some longer-term (15 to 30 year) trends are also shared by most chronologies; narrow rings and high between-tree and between-site correlations were a feature of the first two decades of the Twentieth Century. Similar tree ring patterns, and similar site characteristics suggest that the chronology network described here is suitable for palaeoclimatic reconstruction back to at least 1750.

No description available.

The longest tree-ring chronologies for the Southern Hemisphere published to date go back to A.D. 1011 in central Chile; 1028 in Tasmania, Australia; 1140 in western Argentina; and 1256 on the North Island, New Zealand. For paleoclimatic and other studies longer time series would be very desirable. Here we report on the first successful crossdating and chronology development for Fitzroya cupressoides, a redwood-like conifer in western Argentina, which goes back to 441 and exhibits desirable statistical characteristics.

No description available.

The Midlands and South-west of England are represented by a long oak tree-ring chronology spanning approximately 4500-3900 BC (calibrated radiocarbon dates). The wood on which it is based originates in a technologically advanced trackway crossing the low-lying Somerset Levels, in a coastal submerged forest probably killed by rising sea-level, and in flood-plain oaks washed down the River Trent. Cross-matching between the growth patterns of the three groups of trees is of good quality, yet so far the chronology has failed to cross-date with the long Irish and German dated chronologies. The reasons for this, and the implications of eventual dating, are discussed.