Geoscience Reference
In-Depth Information
circulation indices are often used to evaluate the effects of annual to multicentennial
climate variability and change on ecosystems. The easy availability of these cli-
mate reconstructions is now stimulating a surge of dendroecological research with
a climatic focus.
The fact that synchronous ecological processes occur at very broad spatial scales
questions for both ecology and climatology:
•
How can chronologies and networks of ecological patterns be used to study past
climate variability and change?
•
How does climate entrain ecological disturbance events and population dynamics
(natality and mortality) at regional and broader scales?
•
When and in what manner do climate-forced effects override internal or local
factors (e.g., competition, predation, random variations) in determining the
dynamics of ecosystems?
•
How can we use our understanding of past climate influences on ecosystems
at long-term and broad scales to predict impacts of future climate change on
ecosystem structure, function, and disturbance dynamics?
In this chapter we describe several examples of ecological disturbances and popu-
lation dynamics that are influenced by climatic variations. In particular, we illustrate
how spatial networks are useful for evaluating climatic and ecological relationships
by drawing upon our own fire history, insect outbreak, and tree population studies
in the western United States. In addition to describing and discussing the ecological
insights and implications of these tree-ring studies, we also focus on their relevance
for climatological investigations. We compile both regional tree recruitment and fire
occurrence data to highlight an unusual hiatus of forest fire occurrence in the west-
ern United States and southern South America during the early 1800s as an example
of what we term here as an 'ecologically effective climate change.'
9.2 Examples of Dendroecological-Climate Reconstructions
9.2.1 Fire History and Fire Climatology
Fire history studies using crossdated fire-scarred trees are the most common type
of dendroecological analysis involving assessments of climatic effects. There are
numerous examples of subregional to continental (and even intercontinental) studies
of fire climatology using fire-scar chronologies and various hydroclimatic recon-
fortuitous ecological and physical phenomenon, whereby past fire events (primar-
ily low-intensity surface fires) create very distinctive lesions within tree-ring series
