Climatic Inferences from Dendroecological Reconstructions - Dendroclimatology - page 263

is that these studies provide insights about climate variability that is relevant to
ecosystems, and in turn, human concerns about future climate change impacts on
ecosystems.

Keywords Dendroecology · Forest fires · Insect outbreaks · Tree demography

9.1 Introduction

Dendroecology—the application of tree-ring analysis to ecological questions—is
a rapidly expanding subfield of dendrochronology with increasing relevance to
the study of past and present ecosystems and climatic variations. Ecologists have
typically focused on short-term studies (<10 years) at fine spatial scales (<1000
m 2 ), but the importance of long-term and broadscale processes is increasingly
appreciated (Ricklefs 1987 ; Levin 1992 ; Turner et al. 1993 ; Brown 1995 ) . Many
ecosystem processes, especially those affected by climate changes, manifest them-
selves only over longer time periods and broader spatial scales than encompassed
in typical ecological studies. Understanding the dynamics of long-lived organisms
and ecosystems—and the role of climate in controlling these dynamics—requires
decadal to centennial and landscape- to regional-scale perspectives. Various types
of tree-ring data can provide the depth of temporal and spatial information needed
for multiscale, comparative analyses to fully evaluate climatic effects on ecosystems
(Fritts and Swetnam 1989 ; Schweingruber 1996 ; Swetnam et al. 1999 ) .
The most common types of dendroecological datasets with relevance to studies of
climate effects are disturbance histories (e.g., chronologies of forest fires and insect
outbreaks) and demographic histories of tree populations (chronologies of tree natal-
ity and/or mortality). For both of these types of datasets, there are—or there is the
potential for development of—broad networks of data from multiple sites that allow
for regional-scale analyses. Disturbance and demographic processes are driven by
both internal system dynamics (e.g., species life histories and community dynamics,
such as competition) as well as by external factors such as climate. Generally, evi-
dence for climate effects emerges only at larger spatial and longer temporal scales
because of the 'noise' introduced by local, internal ecological processes. There have
been a variety of dendroecological studies that primarily focused on internal stand
or community ecological dynamics (e.g., Spencer 1964 ; Clark et al. 1975 ; Lorimer
1985 ; Frelich and Graumlich 1994 ; Kneeshaw and Bergeron 1998 ; Morneau and
Payette 2000 ) . These studies were carried out at the stand or watershed scales and
climatic analyses were not included, or they were limited because of the fine spa-
tial scale of the datasets. In contrast, broader studies examining climate effects on
ecosystem dynamics have used network-based approaches involving many sites dis-
tributed across mountain ranges or regions (i.e., 10 4 to >10 6 km 2 ; e.g., Kitzberger
et al. 1997 ; Villalba and Veblen 1997a ; Kitzberger and Veblen 1998 ; Swetnam and
Betancourt 1998 ; Veblen et al. 1999 , 2000 ; Brown and Shepperd 2001 ; Brown 2006 ;
Sibold and Veblen 2006 ; Kitzberger et al. 2007 ) .