Tree Ring Patterns for Ecosystem Ages, Dates, Health and Stress

Summary: Dr. Kevin T. Smith covers ecosystem ages, dates, health and stress that tree ring patterns estimate for non-specialists and specify for dendrochronologists.

tree ring patterns of 357-year-old ponderosa pine (Pinus ponderosa), with five fire scars at 1683, 1693, 1747, 1795 and 1861: Chris Schnepf/University of Idaho/Bugwood.org, CC BY 3.0 United States, via Forestry Images

Tree ring patterns are indicators of local ecosystem ages, dates, health and stress, according to the article Tree Rings and the Local Environment published in the June 2011 issue of Arborist News.

Kevin T. Smith, University of New Hampshire plant biology affiliate professor and USDA Forest Service Northern Research Station supervisory plant physiologist, begins with tree ring counts. Layered growth from "inward cell divisions by the vascular cambium, the new cell generator" between xylem and the inner bark, phloem, can be counted in cross-sections. Ecosystem conditions, genetic programming and tree conditions determine growth since temperate climatic zone alternation of spring and summer growth with winter dormancy produces one annual layer.

Seasonal moisture encourages early-wood ring formation that defies calendar correlations in Mediterranean dry and tropical climates while tropical late-wood expresses El Niño and La Niña cycles.

Extra, false rings from the vascular cambium prematurely deactivating and reactivating during growing seasons frustrate ring-counting ecosystem ages, dates, health and stress from bark to pith. Barrier zones produced by trees after wounding by fires, insects, landscape equipment, storms and vandalism get confused with growth boundaries and misidentified as tree ring patterns.

Diffuse-porous hardwoods such as sugar maples have "narrow vessels scattered across" growth rings, whose boundaries become detectable in finely sanded cross-sections, cut stumps and sawed branches. Conifers such as red cedar and spruce involve thick-walled late-wood tracheids growing late in the season before thin-walled early-wood tracheids grow early in the next season.

Ring boundaries in such ring-porous hardwoods as ash, locust and oak join one year's fine-pored, late-formed summer vessels and the next year's early-formed, wide spring vessels.

Growth stimulation from the forest canopy's sunlit openings and growth suppression by fungal infections or in closed canopies keep tree ring patterns respectively wide or tight-spaced.

Cores extracted from trunks through increment borers, cut stumps and sawed branches let dendrochronologists specify the "calendar year of wood formation" for all area tree rings.

Dendrochronologists comparatively measure core samples from area trees for chemical characteristics, early-wood to late-wood proportions, late-wood and ring widths, resin canals and scars and wood density. They need marker years, "unusual rings" in essentially all trees in a study area or region," and measurements for cross-dating ecosystem ages, dates, health and stress.

Cross-dating offers precise, not estimated, years for tree ring patterns while marker years operate to date archaeological samples, area dead and living trees and wooden structures.

Core samples, cut stumps, electric planes used across the grain, increment borers, modeling and statistical techniques and sawed branches provide dendrochronologists with the tools for cross-dating.

Such "environmental processes of forest dynamics" as pest outbreaks, recurring fires and variable light, precipitation and temperature qualify as events whose timing dendrochronological tools can establish. Narrow, tightly spaced tree ring patterns reveal such ecosystem stresses as defoliation by red spruce budworms in northern Maine in 1920, extreme drought and reduced sunlight. Wide tree ring patterns show ecosystem health, sunlit canopies and wet years while Colorado Front Range fires in 1915, 1933, 1956 and 1980 scar Fremont cottonwoods.

Tree ring patterns tell dendrochronologists specifics of ecosystem ages, dates, health and stress and master gardeners, master naturalists and tree stewards estimates of area tree ages.

Helene Løvstrand Svarva, Fellow at NTNU (Norges teknisk-naturvitenskapelige universitet; Norwegian University of Science and Technology), takes samples June 28, 2008, with increment borer in Sogndal, Sogne og Fjordane County, western Norway: Terje Thun, NTNU Vitenskapsmuseet Museum of Natural History and Archaeology (NTNU Vitenskapsmuseet), CC BY 2.0 Generic, via Flickr

Acknowledgment

My special thanks to:
talented artists and photographers/concerned organizations who make their fine images available on the internet;
University of Illinois at Urbana-Champaign for superior on-campus and on-line resources.

Image credits:

tree ring patterns of 357-year-old ponderosa pine (Pinus ponderosa), with five fire scars at 1683, 1693, 1747, 1795 and 1861: Chris Schnepf/University of Idaho/Bugwood.org, CC BY 3.0 United States, via Forestry Images @ http://www.forestryimages.org/browse/detail.cfm?imgnum=1171013

Helene Løvstrand Svarva, Fellow at NTNU (Norges teknisk-naturvitenskapelige universitet; Norwegian University of Science and Technology), takes samples June 28, 2008, with increment borer in Sogndal, Sogne og Fjordane County, western Norway: Terje Thun, NTNU Vitenskapsmuseet Museum of Natural History and Archaeology (NTNU Vitenskapsmuseet), CC BY 2.0 Generic, via Flickr @ https://www.flickr.com/photos/38254448@N05/4024813881

For further information:

Gilman, Ed. 2011. An Illustrated Guide to Pruning. Third Edition. Boston MA: Cengage.

Hayes, Ed. 2001. Evaluating Tree Defects. Revised, Special Edition. Rochester MN: Safe Trees.

Marriner, Derdriu. 9 April 2011. “Benignly Ugly Tree Disorders: Oak Galls, Powdery Mildew, Sooty Mold, Tar Spot.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/04/benignly-ugly-tree-disorders-oak-galls.html

Marriner, Derdriu. 12 February 2011. “Tree Load Can Turn Tree Health Into Tree Failure or Tree Fatigue.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/02/tree-load-can-turn-tree-health-into.html

Marriner, Derdriu. 11 December 2010. “Tree Electrical Safety Knowledge, Precautions, Risks and Standards.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2010/12/tree-electrical-safety-knowledge.html

Smith, Kevin T. June 2011. "Tree Rings and the Local Environment." Arborist News 20(3): 12-16.
Available @ http://viewer.epaperflip.com/Viewer.aspx?docid=20477746-09e1-496a-9639-a2bc0101cd42#?page=14