Dendroecology

March 31, 2015

Dendroecology• Dendroecology is the analysis of ecological issues

such as fire, insect outbreaks, and stand-age structure with tree rings

• Was developed by Theodor Hartig and Robert Hartig in late 1800s Germany

• In the US, dendroecology did not develop until the 1970s with the work of Hal Fritts

• Since the 1970s, dendroecology has come to include fire history, insects, masting, stand-age structure, pathogen outbreaks, and endogenous disturbance history

Stand-Age Structure

• Usually the first step in other types of dendroecological studies

• Stand-age structures required all living and standing dead trees be sampled in a specified plot to quantify the current forest composition and past conditions

• This provides establishment and mortality history of all tree species on the plot

Gap-Phase Dynamics• Where trees respond to

openings in the canopy caused by mortality or cutting of dominant trees

• Ring widths record suppression and release events

Dendropyrochronology

• Reconstruction of fire histories is one of the major applications of dendrochronology for use in management of forests and the reestablishment of fire as a disturbance agent

• The goal of the dendrochronologists is to determine the natural range of variability for fire on a particular site, which describes …

Fire Regimes

• A natural fire regime is a general classification of the role fire would play across a landscape in the absence of modern human intervention, but including the influence of aboriginal burning.

• In the southeastern US, there have been 5 different fire regimes

Fire regimes:• Fire frequency: how often

• Fire seasonality: when fires occur throughout the year

• Fire severity: effects on forests – not a measure of fire temperature

• Fire intensity: a measure of fire temperature

• Fire extent: spatial aspects

• Patchy fires versus landscape level fires

• Fire variability: changes in fire over time and space

• Climatic or human-driven?

• Fire-tolerant species – species that are able to survive fire events– Examples – most pines (excluding white pine) and

several species of oak

• Fire-intolerant species – species that are not able to survive fire events– Examples – maples, tulip poplars, sycamores,

gums

Southeastern Fire Regimes

Fire exclusion – the most successful ad campaign ever…

The fire-scar record from tree rings.

Catface on Table Mountain pine log, Reddish Knob, Virginia

Fire scars

The fire-scar record from tree rings.

Fire scars on ponderosa pine, El Malpais National Monument, New Mexico

Notice how the tree tries to compartmentalize the fire scar wound by growing succeeding years around the wound.

Detail of fire scar on ponderosa pine, El Malpais National Monument, New Mexico

Fire Seasonality

Insect Outbreaks

• Dendroentomology: The science that uses tree rings to date and study the past dynamics of insect populations

• Gives understanding of insect population dynamics, including duration of outbreaks, interval between outbreaks, and spread of insect outbreaks

• Julius Ratzeburg

Historic Insect Outbreaks• In the past, insects outbreaks were controlled through disturbance events – mainly

fire

Close-up of a cross section of a ponderosa pine (Pinus ponderosa) from Oregon, showing periods of growth reduction caused by Pandora moths. Note the narrow rings that begin around 1631, 1661, and 1677.

Besides fire suppression, climate change increases insect outbreaks?

• Bark beetle outbreaks are a result of four interacting factors:

• The factors that control the initiation, spread, and termination of insect outbreaks are complex, and involve a combination of climatic conditions and characteristics of forest stand structure.

Sudden Oak Death

Sudden Oak Death

Bleeding cankers on tan oak

Leaf dieback in rhododendron

Sudden Oak Death

Gypsy Moth• Originally evolved in Europe and Asia and has existed there for

thousands of years.