Cores of red spruce (Picea rubens Sarg.) from three upper-elevation sites in Maine, U.S.A., were X-rayed, and minimum and maximum wood densities as well as ring widths were mechanically recorded. The 200- to 300-year series of maximum densities at the three sites show remarkable inter-site similarity. Maximum density and total ring-width series from one site, Elephant Mt., were standardized. Response functions, which measure tree-growth response to climatic variables, were calculated for each of these two series. The ring-width response function explained 66% total variance, of which 34% was explained by climate. The maximum density response function explained 70% total variance, 67% of which was explained by the same climatic variables. Thus, the climate signal from maximum densities is stronger, and perhaps more season-specific, than that of ring widths.

No description available.

The separating distance over which tree-ring chronologies are significantly correlated is investigated. Any chronology occuring within a radius of 161 km of another is estimated to contain at least half of the common variance occurring at zero separating distance. The separating distance of 161 km is used to calculate the number of nonoverlapping chronology equivalents present within the 40 -, 65 -, and 89-chronology western North American grids. The density of chronologies is calculated for these three grids in various ways. The results give conservative density estimates of five, seven, and eight sites per Mkm² for the three different tree-ring grids.

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.