Why We Monitor Them
forest stressors and the factors that influence them probably has expanded
more in the past 25 years than in the entire previous century. Our knowledge
of climatology, soils, pathogens, insects, plant physiology, anthropogenic
influences, and other factors has increased at an almost geometric rate.
Perhaps more importantly, scientists have come to appreciate the role
that these stressors play in interaction with one another.
In other words,
our knowledge of the cause-effect relationship is clearer than ever
before. Earlier land managers and scientists often erred in assigning
one condition as the cause (e.g., southern pine beetle) without recognizing
the underlying influences that triggered the condition (e.g., not matching
the planted tree species to the site). Today, investigative forest resource
scientists take a much more holistic approach to analysis of conditions
as reflected in stressed trees.
this increased understanding of tree-environment dynamics has been a
fortuitous and equally impressive ability to track, record, and analyze
stressed conditions. This understanding has come none too soon. Without
sophisticated detection and analysis equipment, the vast amounts of
data accumulated over the past two or three decades could scarcely be
tabulated, let alone analyzed and interpreted. To cope with the explosion
of information, high-technology tools are necessities, not luxuries.
Examples of such tools are geographic information systems (GIS), global
positioning systems (GPS), satellite imagery, and highly refined aerial
reconnaissance methods. Our present ability to collect and tabulate
an enormous volume of data has led to an opportunity probably never
envisioned by most scientists in the first half of the 20th century-the
capacity to perform complicated, computerized, statistical, and spatial
analysis on investigations into large-scale environmental change. As
just one example of such high-technology investigative work, scientists
have given birth to a new branch of dendrochronology (the study of tree
age) in which analyses are made of tree rings to determine the chemical
composition of the environment decades ago so it can be compared with
the composition today.
Many of these new
analysis methods have applications not only with contemporary information
but also with data chronicled long ago. Retired scientists are no doubt
heartened to see their work reanalyzed and depicted using contemporary
methodology. One example is historical records on the southern pine
beetle included in figure 22.
Using modern tools
and land managers, environmental scientists are establishing baseline
data that doubtless will prove valuable in determining whether conditions
such as global warming and tropical deforestation are impacting geographic
areas ranging in size from a stand of white pine trees in North Carolina
to the health of the entire planet earth.
As dramatic as
advances have been in recent years, technology continues to grow more
and more sophisticated at an exponential rate. Software and hardware
engineers, photogrammetrists, statisticians, and environmental scientists
are coordinating their efforts to maximize the utility of their different
disciplines. So rapid are these advances that the technology described
in this publication likely will become obsolete in a few years.
Forest Health Protection
is important to the public in many ways, from the forest products used
in everyday life to the quality of the environment. Also, the same insects
and diseases that damage forests can affect trees in residential and
other nonforest areas.
To assist readers
of this publication who are not familiar with forestry terms, a glossary
has been placed at the end of the text. A list of the common and scientific
names of the pests and the hosts that are discussed appears in appendix