Time-related region-wide growth declines or increases due to environmental impacts are not readily detected in rings of young trees because the intrinsic age-related decrease in ring widths is too prominent. Standardization techniques often obscure gradual growth changes due to exogenous factors such as regional atmospheric deposition. The model presented here uses a linear aggregate analysis of ring widths that permits age to be held constant while time varies. Rigorous testing requires tree-ring observations from evenaged stands exhibiting a range of current ages normal for the species and region. With age held constant, the key variable is simply the calendar year to which given rings are dated, a measure of the passage of time. An application of the model is given in which a 36 -year growth decline is identified in 20- to 40- year-old Pinus taeda L. in the southeastern United States.

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.

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.

Annual rings of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, which sustained 1 year of defoliation by the western false hemlock looper, Nepytia freemanii Munroe (Lepidoptera: Geometridae), showed a period of decrease in breast height ring width starting in the year that followed the damage. The magnitude of the decrease was related to the degree of defoliation: there was no ring width decrease on trees that were 0-10% defoliated; the decrease became progressively more noticeable in trees which sustained increasingly higher defoliation; and it was maximum in trees which sustained 91-100% defoliation. This period of reduction lasted 1 to 5 years and was followed by a period of above-normal growth which was related to defoliation in a similar manner: it was absent in trees 0-10% defoliated and maximum in the 91-100% tree defoliation class. Increase in defoliation caused a significant increase in index standard deviation, autocorrelation and mean sensitivity.