Sixteen modern Nothofagus solandri tree-ring chronologies, developed from sites near the alpine timberline, South Island, New Zealand are presented. The statistical properties of the chronologies are similar, having high mean sensitivity values (mean of 0.34), moderate autocorrelation values (mean of 0.50), and high common variance values (mean of 42 %). However, the chronologies are mainly less than 300 years in length. Examination of interchronology variation suggests that the similarity between two chronologies decreases with increasing distance. It is concluded that these chronologies offer considerable potential for reconstructing palaeoclimates, especially palaeotemperature.

Spline functions were examined and compared with conventional polynomials for use in filtering nonclimatic variance from tree-ring width series. Both types of curve were fitted to ring-width series exhibiting particularly marked effects of competition and release from competition with neighboring trees during the last 100 years. Available climatic data from that interval were used to statistically evaluate the capabilities of each type of function for removing nonclimatic effects and preserving the climatic signal. The results suggest that both types of function can be used successfully for those purposes, though in the presence of extremely rapid changes in growth rate due to a sudden release from competition it may be necessary to divide the ring-width series into two segments and fit a separate curve to each segment. Tightly-fit polynomials seem to be about as effective as splines, but are less desirable from a computational point of view as, for example, when the magnitude of the (negative) exponents of the coefficients exceeds computer capacity. Further, a spline function can be prescribed from its frequency-response characteristics, so it is possible to specify in advance the extent to which it will filter out any potential climatic cycles.

A simple method of testing the statistical significance of the summary response function derived by Pilcher and Gray is given and applied to European oak data.

Five modern Nothofagus menziesii tree-ring chronologies, developed from sites near the alpine timberline, South Island, New Zealand, are presented. The properties of the chronologies are described; as a group they have high mean sensitivity values (mean of 0.31), moderate autocorrelation values (mean of 0.42) and moderate common variance values (mean of 31 %). One site, lying some 200 km distant from the others, is the least similar of the five chronologies. It is concluded that both the long length of N. menziesii chronologies and the proximity of trees to the alpine timberline present considerable potential for reconstructing palaeotemperatures.

Populus balsamifera grows farther north than any other tree in North America. In northern Alaska, these trees have clear annual growth rings, and reach ages over 230 years. High year-to-year variability in ring widths permitted ready crossdating. A chronology prepared using paired cores from 16 trees exhibits mean sensitivity (0.48) and standard deviation (0.50) values much higher than those obtained from most conifer species in the Arctic. First order autocorrelation (0.43) is also lower than most Arctic species. A strong correlation (r =0.47) with June temperature suggests balsam poplar may provide a good record of growing season temperature.

Dendrochronological problems in dating tropical tree species are responsible for a large gap in global dendroclimatic reconstructions. Study of Cedrela and Juglans in the low-latitude forests of northern Argentina and Bolivia has resulted in development of four chronologies. These genera have good tree-ring characteristics, and statistics indicate that they have good potential for dendroclimatology. Longer series should be obtained from older stands.

Two independent local tree-ring chronologies of oak in the Netherlands are described. Chronology I contains recent wood, wood from mills, and paintings. This chronology begins in A.D. 1973 and goes back to 1385 and is thought to be from inland areas of the Netherlands and the adjacent German area. Chronology 11 is built up from paintings and sculptures and ranges from A.D. 1623 to 1140; the origin of the wood is presumed to be from a coastal site in the Netherlands.

Huber identified in samples from the forests of central Europe features for characterising by their wood structure the two species of British oak. We have confirmed for recently felled oaks the suitability of his method of analysis and applied it to timbers from ancient buildings and to samples from sub-fossil oaks. The two species appear to have persisted in separate locations during the last ice age. Such analysis of the numerous Holocene oaks in Europe now being dated by den - drochronology offers the possibility of studying the separate migration of the species.

The variation in wood density within growth rings was determined from X-ray negative images of wood samples of Gmelina arborea. The within-tree and between-tree comparisons showed that no two growth rings had exactly similar patterns of variation in the radial direction. The proportions of wood in four within-ring density classes were estimated. The variations in the proportions of wood in the four classes with age were nonlinear. On the average, the proportion of low density wood decreased with increasing age, while the proportion of high density wood increased with age. Regression analysis testing different curvilinear models showed that 37 to 99 per cent of the variations in the proportions of wood were associated with variations in age. Maximum and minimum ring density were negatively correlated with dry season rainfall. Variations in the proportion of high density wood and mean ring density were not associated with corresponding variation in dry season rainfall. The proportions of low and high density wood, mean ring density, maximum ring density and minimum ring density were not determined by annual rainfall.