Preliminary relationships between climate and the apical extension, needle production and ring width of Pinus ponderosa in Arizona, USA

Abstract

Measurements of apical extension (height increment), needle production and ring width from a detailed sequence of measurements on one Pinus ponderosa tree from the Santa Catalina Mountains, southern Arizona, USA for the period 1962 - 1998 are presented. From these measurements the relationships between tree age and height, and tree height and diameter at breast height are determined. These are compared with the overall site trends for the same relationships determined from height and basal age of individual trees, and the site ring width chronology to test whether the growth of the individual tree is comparable with that of other trees at the study site.

Needle production and apical extension are highly correlated (r = 0.67) and show generally similar climate correlations. Ring widths are not significantly correlated with either of these series but all three series are significantly positively correlated with precipitation and dew point temperature during the relatively dry months of March, April and May of the growth year. This seems to be the dominant factor influencing ring width growth. However, needle production and apical extension also appear to be related to both climatological conditions during the year of bud formation as well as during the year of growth. These relationships can be explained by either bud formation processes, depletion of stored carbohydrates that would otherwise be used for bud formation or variations in the rate of apical growth. Further data are required to support some of the climate relationships.

Although there was suppression in the early growth of the individual tree, for the periods when the needle density data and isotope tracer results apply, growth of the individual tree corresponds with average site growth trends. Given this consistency, it is not unreasonable to use the needle production and stable isotope tracer results, which are only available for this tree, to calibrate, verify and parameterise the Tree Ring model.