May 20, The Historical Ecology Handbook:
Establishing Reference Conditions Figure 1. The thick, horizontal limbs of this old pine show that it grew in the open.
Restoring southwestern ponderosa pine forests revolves around reintroducing a regime of frequent, low-intensity fires like those that historically maintained forest structure and function. Such fires were rare in the twentieth century, due to livestock grazing and widespread fire exclusion.
The resulting buildup of woody fuels has caused a widespread crisis in forest health, the effects of which include huge and unnaturally severe crown fires, bark beetle outbreaks, and declining Dendrochronology determining reference ecosystems and the.
Restoration treatments that include prescribed burning, often preceded by thinning to reduce fuel loads, have the potential to improve the ecological health of these forests. Restoring conditions similar to those of the evolutionary environment is not a matter of trying to return to the past; rather, it is the only way to assure the long-term health of these forests into the future.
This publication provides ideas about how to determine some reference conditions for southwestern ponderosa pine forests, using both physical and cultural evidence.
Limitations of Reference Conditions Reference conditions can serve as an important guide for future management, but it is important to emphasize that reference conditions are not the same as restoration goals.
Some types of reference information, such as detailed data about understory vegetation, small trees, wildlife, and the degree to which native peoples burned forested areas, are simply not available for most periods in the past. Even where reference conditions are known, it is often not possible to fully re-create the conditions present before Euro-American settlement, as climate change, extirpation of native species, habitat fragmentation, and the introduction of nonnative species have irreversibly changed contemporary conditions.
In many cases, it might not be desirable to return to presettlement conditions, due to considerations of wildlife management, recreation, aesthetics, and other modern needs.
For example, dense thickets of small trees can provide cover for wildlife and visual screening along roads or near houses. Above all, each restoration treatment needs to be site-specific.
Reference conditions will never provide a recipe for forest management, but they can help set restoration and management goals. Clues about reference conditions are a particularly powerful tool when multiple lines of evidence are used to create a fuller picture than one type of evidence alone could.
Evidence for reconstructing reference conditions comes in two forms: Physical Evidence Some of the best clues about what forests were once like occur in the forests themselves, in the form of contemporary forest structure and old trees, alive or dead, that indicate how that structure has changed.
Old Forest Remnants One of the best ways to understand what a given forest area might look like under a restored fire regime is to analyze nearby areas that are less degraded and therefore more closely resemble what presettlement forests looked like. Parts of the North Rim of the Grand Canyon, for example, have never been logged, have not been grazed by livestock for many years, if ever, and have experienced wildfires on a regular basis.
Some other large protected areas, such as parts of the Gila Wilderness and El Malpais National Monument in New Mexico and Zion National Park in Utah, have also been examined for important clues to the past of southwestern forests. Small remnant sites that can help illustrate what forest structures were once like may also exist elsewhere, such as on or near steep slopes where topography made logging or grazing impossible.
Comparing nearby forest stands to those sites can help quantify the changes in forest structure that have resulted from modern management practices. It is important not to extrapolate too much from such sites, though, as forest structure and fire regimes can vary a great deal in a small area, especially where topography or other ecological conditions are varied.
Physical Remains of Old Trees Trees present before Euro-American settlement are an obvious source of information about forest structure at an earlier time. While many of the trees standing at that time have either been logged or died naturally, their remains often persist for many decades in the arid climate of the Southwest.
Searching for these remains can help establish some of the most accurate records of past forest structure. The bark of ponderosa pine trees generally begins to turn yellow at about a hundred years of age White Most restoration treatments being implemented in the Southwest call for retaining and protecting all yellow-barked pines, since these old trees are among the rarest resources in southwestern forests.
Though no such guide exists for the Southwest, two useful publications that are available online detail how to determine the age of ponderosa pines in the Colorado Front Range Huckaby et al.
The growth forms of ponderosa pines can also aid in reconstructing past forest structure. For example, trees grown in open conditions typically have full, rounded crowns and relatively long, thick branches Figure 1while trees grown in a closed forest more often appear long and narrow.
These appearances persist even if stand conditions later change. A few old, open-grown pines surrounded by a sea of smaller, younger trees likely indicates that forest structure was once more open than it is now.
Such scars often preserve evidence of many fire events, which can be dated using the dendrochronological techniques described below.
A comparison of the species represented by old and young trees can also be telling. Dead trees can stand for many years in the Southwest, particularly if they are large Figure 3.
The Historical Ecology Handbook: a Restorationist’s Guide to Reference Ecosystems,. is derived from the seminar proceedings of a restoration ecology conference, but its contents are widely applicable to researchers and practitioners involved in the study and conservation of both biological and cultural diversity. Professionals buy handbooks such as this one to keep current on research. Identiﬁcation of Old-Growth Forest Reference Ecosystems Using Historic Land Surveys, Redwood National Park, California Joy A. Fritschle1,2 Abstract Old-growth forests in the American West typically rep-resent fragments of former, more extensive forests that were subjected to nineteenth and twentieth century land-clearing activities, such as logging. In summary, the The Historical Ecology Handbook: a Restorationist’s Guide to Reference Ecosystems is a very good starting point for students, researchers, and practitioners in a wide range of fields, and is affordably priced. This book is an excellent first resource for practitioners with restoration or interpretation tasks before them in less well-studied systems.
They provide important wildlife habitat for such species as bats and cavity-nesting birds. Their size, age, and growth form provide the same sorts of clues to forest structure as living trees.
Like a living tree, this snag records growth forms that show how it grew. Especially where fire has long been absent, fallen logs can persist for decades on the forest floor Figure 4. They can indicate the position, size, and age of old trees.
In some parts of the Southwest it is possible to find stumps 16 or 32 feet away from remnants of tree tops, indicating that early loggers removed only the commercially valuable lower sections of trunk wood.
Downed logs can remain on the forest floor for many decades, providing clues about old forest patterns. Their size gives an idea of the size and species of the trees removed; their rings can be cross-dated to establish their age and growth rates; their spatial arrangement reflects forest structure before logging.Kipfmueller, K , Using dendrochronology to reconstruct the history of ecosystems.
in D Egan & E Howell (eds), The Historical Ecology Handbook.
Island Press. Identiﬁcation of Old-Growth Forest Reference Ecosystems Using Historic Land Surveys, Redwood National Park, California Joy A.
Fritschle1,2 Abstract Old-growth forests in the American West typically rep-resent fragments of former, more extensive forests that were subjected to nineteenth and twentieth century land-clearing activities, such as logging.
Richard H. Waring, Steven W. Running, in Forest Ecosystems (Third using FOREST-BGC show that process simulation models link growth with climate more closely than do more empirical dendrochronology models. function of tree age.
The sapwood rings represent the outer years of growth (equivalent to the intercept). By determining the. Using dendrochronology to reconstruct the history of forest and woodland ecosystems. Pp. – in The historical ecology handbook: A restorationist’s guide to . Dendrochronology is an important technique in a number of disciplines, including archeology, paleontology, paleobotany, geomorphology, climatology, and ecology.
Forensic applications concern the dating of wooden objects and matching objects with crime scenes using the wood ’ .
The reference presettlement conditions can be applied to management of this ecosystem in two ways. First, reference conditions are a benchmark against which to .