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variability, such as that caused by tree age/size trend and interactions with neighbors, limit
the faithful representation of climate variations on centennial and longer timescales in many
cases.
Overcoming the weaknesses of dendroclimatology may require more creativity
than making best use of its strengths. It is time to reframe the way tree rings are
used as natural archives. Specifically, this reframing would involve:
1. Thinking of the tree ring as a natural archive that contains several potential proxy
records of climate, whose mutual relations contain information about multiple
environmental factors; these would include total and partial ring widths, density
variables, microanatomical measurements, ratios of stable isotopes (see Gagen
et al.
Chapter 6
, this volume), and potentially trace chemistry.
2. Using a combination of improved process-based modeling and empirical-
statistical approaches to produce an integrated understanding of why the various
proxy records in a ring vary through time and within the tree; this would include
consideration not only of the mechanisms producing interannual variations in
the various proxies (see Cook and Pederson,
Chapter 4
, this volume; Vaganov
et al.
Chapter 3
, this volume), but also how and why this interannual variabil-
ity changes according to cambial age and tree geometry (see Briffa and Melvin,
Chapter 5
, this volume).
3. Placing these processes in a spatially explicit context of the forest and the land-
scape; events in neighboring trees, and in the forest and landscape more broadly,
clearly influence ring formation, and the character of each tree-ring record (see
Swetnam and Brown,
Chapter 9
, this volume). Given recent developments in
the modeling of forest dynamics, remote sensing, and geospatial analytical tech-
niques, it should be possible to put the treatment of these influences on a more
quantitative basis than hitherto.
4. Using ecological information based on dendrochronology as a source of climate
information with relevance to forests and woodlands (see Swetnam and Brown,
Chapter 9
, this volume); there is particular promise in developing understand-
ing of fire climatology and expanding dendroecological fire history networks to
continental and global scales.
5. Reconciling the multiple proxies available from a tree-ring record internally
in terms of mechanisms and known relationships, and then reconciling them
with independent proxies from other natural archives; in the best case, this
will involve tree-ring proxies and independent proxies providing estimates of
processes linked by known, measurable mechanisms—for example, linking a
tree-ring-based precipitation reconstruction through streamflow to the variation
of lake levels recorded by geomorphic or sediment isotope records (for example,
of different components of a system, such as precipitation in the headwaters
and the level of a receiving lake, it is possible to test the mutual consistency of
the reconstructions quantitatively, and not merely to track covariation. Did, for
example, the precipitation as reconstructed vary enough and at the right time to
