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Dendroecology

Dendroecology is the use of tree-ring dating techniques to examine ecological questions. This article explores the multitude of applications and major uses of dendroecology, including dating ecological events, reconstruction of tree population dynamics, and understanding the impacts of natural and anthropogenic causes. Specific applications include disturbance ecology, forest dynamics, and animal populations. Dendroecology offers a high degree of temporal precision and promotes interdisciplinary research.

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Dendroecology

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  1. Dendroecology An important tool for understanding forest dynamics

  2. Dendroecology Defined: • Dendroecology is the use of tree-ring dating techniques to examine ecological questions. • Multitude of applications • Can be used to understand the how, why, and when of ecological changes

  3. Major Applications of Dendroecology: • Dating of specific ecological events (biotic and abiotic). • Cambial Scars or other injuries • Changes in growth rates • Reconstruction of tree population dynamics • Tree births and deaths • Patterns of species change • Growth and productivity changes • Natural and anthropogenic causes • Biosphere-Geosphere Interactions (e.g., climate)

  4. Specific uses of tree-ring data to solve ecological questions: • Disturbance Ecology • Fires (already discussed) • Insects/Pathogens • Weather related disturbances (blow downs, hurricanes, or ice storms) • Forest Dynamics • Succession Studies • Reconstruction of past conditions • Nutrient dynamics • Animal Populations

  5. Insects/Pathogens • Two Approaches: • Determination of Death Dates • Comparison of Growth Rates • Host vs. Non-host growth changes • Growth changes due to differential mortality • Growth reduction due to infection by pathogens

  6. Death Dates

  7. Death Dates

  8. Rapid Growth Changes • Growth Suppressions: Rapid reduction of growth from on year to the next, usually extending for several years duration. • Typically caused by defoliating insects such as spruce budworm or tent caterpillar. • Growth Release: The opposite of a suppression; growth rapidly increases for several years. • Typically due to the death of overstory trees which frees up resources for surviving trees.

  9. An example of a growth suppression in white fir defoliated by spruce budworm

  10. Growth Releases From Veblen et al., 1991

  11. Hey! What about climate?!?! • To be sure growth suppressions are not due to climatic factors we need to examine both host and non-host tree species. • We also need to be sure that the host and non-host trees have similar climatic responses. • Once we account for the effects of climate in the tree-ring series we are left with an index of insect defoliation, indicated through growth suppressions.

  12. Dated Host Tree Increment Cores Dated Nonhost Tree Increment Cores Measurement of cores Measurement of cores Raw ring width measurements Raw ring width measurements Check dating and measurements (COFECHA) Check dating and measurements (COFECHA) Standardization (ARSTAN) Standardization (ARSTAN) Standardized Host Tree Summaries Standardized Control Chronology Remove climatic variation from host tree summaries (OUTBREAK) Corrected Indices Outbreak definition rules (duration and threshold) Outbreak Periods Verification with Historical documents From Ryerson, 1999

  13. Lime Creek and nonhost chronology Host (Douglas-fir) Nonhost (pine) Documented outbreak Inferred outbreak 2.0 x e d 1.5 n i g n 1.0 i r - e e 0.5 r T 0.0 2.0 x e d 1.5 n i d e 1.0 t c e r 0.5 r o C 0.0 1650 1700 1750 1800 1850 1900 1950 2000 Year From Ryerson, 1999

  14. Normalized corrected site chronology from Demijohn Peak with six different standardization pairs 2 1 1 0 -1 -2 2 s t i n u n 3 o i t a i v e d 4 d r a d n a t S 5 6 1650 1700 1750 1800 1850 1900 1950 2000 Year From Ryerson, 1999

  15. Forest Dynamics • Internal Dynamics • Species life history traits • Interactions/competition for limited resources • External Factors • Primarily disturbance (anthropogenic or natural) • Long term changes related to climatic factors

  16. Forest Dynamics: Successional Change • Understanding how forests change in structure and composition through time is an important part of determining mechanisms of change as well as the consequences of human activities. • Two main approaches: • “Snap Shots” • Temporal patterns

  17. From Arno et al., 1997

  18. From Donnegan and Rebertus, 1999

  19. Animal Populations: The Next Frontier • Cambial Scarring • Beavers, porcupine, caribou migration etc… • Growth Reductions • Blue herons—nesting • Moose browsing

  20. Porcupine Feeding (Spencer, 1964)

  21. The Strengths of Dendroecology • Historical perspective • High degree of temporal precision (annual and sometimes seasonal) • Incorporation of dead material to develop long chronologies of change not possible using simple ring counts • Promotes interdisciplinary research

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