GEOG. 4371 TAKE HOME FINAL EXAM

(80 points)

Answer the following question in a total of no more than 1500 words (i.e., 6 typed, double-spaced pages). DO NOT EXCEED THE 1500 WORD LIMIT ON LENGTH. I will accept neatly hand-written answers, but I prefer typed answers.

The exam is due by 10 a.m. on Monday, Dec. 13 . Either leave it in my mailbox in Geography 110 or at my office (Guggenheim 201a). You can slip the exam under my office door.

Late exams will not be accepted without prior arrangement. If you have an emergency that will prevent you from turning in the exam on time, let me know by email (Veblen@colorado.edu) or voice mail (492-8528) before 10 a.m. on Dec. 13.

General Background

Political leaders and many resource management professionals often stress the convergence of the goals and strategies of fire hazard reduction and ecological restoration in the forests of the western United States. For example, the official position of the Society of American Foresters in response to the 2000 fire season included the statement that:

“The buildup of combustible materials (fuels) in the forests of the West is at an all-time high. Much of this can be attributed to the decades of fire suppression that allowed the fuels to build up so fires will now burn bigger and hotter than ever” -- Society of American Foresters, August 11, 2000 press release.

There is a widespread belief among resource managers that fuel accumulation during many years of fire suppression in western forests was the major cause of the widespread wildfires of the 2000 and 2002 fire seasons. Likewise, there is a consensus that a perceived decline in “forest health” (increased mistletoe infection, and increased outbreaks of forest insect pests) is the result of fire exclusion.

The view that current fire hazard is largely attributable to fuel buildup under decades of fire exclusion is strongly reflected in the following passage from the 2001 National Fire Plan:

“While the policy of aggressive fire suppression appeared to be successful, it set the stage for the intense fires that we see today. ...after many years of suppressing fires, thus disrupting normal ecological cycles, changes in the structure and make-up of forests began to occur. Species of trees that ordinarily would have been eliminated from forests by periodic, low-intensity fires began to become a dominant part of the forest canopy. Over time, these trees became susceptible to insects and disease. Standing dead and dying trees in conjunction with other brush and downed material began to fill the forest floor. The resulting accumulation of these materials, when dried by extended periods of drought, created the fuels that promote the type of wildfires that we have seen this year.”

This “fire exclusion/fuel buildup” perspective on current fire hazard in western U.S. forests is the main scientific argument behind the 2003 Healthy Forests Restoration Act (HFRA). In relation to HFRA, Congress has mandated that federal land managers evaluate the degree and nature of the departure of current vegetation and fuels from historical conditions. In other words, the belief that fire hazard mitigation is coincident with ecological restoration is now ingrained in national legislation.

The Science-Management Protocol

The USDA Forest Service has recently developed an index of Fire Regime Condition Class (FRCC) for prioritizing fuels and restoration treatments. The goal is to provide a framework to “restore healthy, diverse and resilient ecological systems to minimize uncharacteristically severe fires...” The FRCC index indicates how much current forest structures and recent fire regimes have departed from their historic condition (i.e. prior to the beginning of fire suppression in the early 1900s). Under the FRCC protocol, each forest type (e.g. ponderosa pine, spruce-fir etc.) in a major biogeographical region (e.g. the Pacific Northwest, southern Rockies, etc.) is assessed by determining the departure between current and past vegetation conditions based on the application of the concept of Potential Natural Vegetation Types (PNVTs).

The PNVTs are based on “plant species that are indicators of the natural disturbance regime, site climate and soil relationships.” The PNVT concept is essentially the same as Daubenmire’s concept of “habitat type” (described on p. 156 of Kimmins’ textbook). For each PNVT a model of reference conditions of the historic fire regime (i.e. fire frequency and severity prior to c. 1900 A.D.) and associated vegetation conditions (e.g. vegetation structure) is determined by consulting the published research literature and through the use of “expert opinion.” Expert opinion includes the opinions of both published researchers (a minority) and of vegetation managers (a majority), and is very important for filling in the gaps in the published literature.

Literature review and expert opinion are also used to determine successional patterns and time periods required for succession to pass through a series of structural stages. In most cases the structural stages are identified by the amount of tree crown closure (i.e. canopy cover) from open early seral stages to closed late stages.

The information on historic fire regime is combined with this information on successional patterns (especially times required for transitions from one structural stage to another stage) to reconstruct reference forest conditions. This procedure involves the use of a vegetation dynamics model in which the probability of disturbance (fire) is input and the model is run repeatedly until the PNVT stage composition is stabilized. In other words, the model yields an estimate of the percentage of the area for each cover type that would have been in different structural stages (i.e. different amounts of tree canopy closure) based on the given amount of past burning. These proportions of the landscape in different structural stage are assumed to represent the landscape during the reference period (e.g. for at least several hundred years prior to c. 1900 A.D.).

As an example, a draft model for the ponderosa pine cover type in Colorado indicated the following percentages of the landscape in each structural stage: A) 15% in open areas dominated by grass and shrubs; B) 5% in dense stands of small trees (less than 7 inches diameter) with > 30% canopy cover; C) 25% in less dense stands of small trees with < 30% cover; D) 50% in stands with < 30% canopy cover of large-diameter (>7 inches) ponderosa pine; and E) 5% in stands with > 30% canopy cover of large-diameter mainly ponderosa pine and some Douglas-fir. These percentages are then taken as the average reference conditions, and managers must determine the degree to which the modern landscape departs from those percentages. It is assumed that rare high severity fires can occur in stages B and E, but that 90% of the fires are surface fires and occur in stages C and D.

The fire input parameter to the draft model was derived from the mean composite fire-interval. I described this concept in the class on fire history methods. The fire parameter inputs are being modified, especially to take into account differences between habitat types formerly characterized by mostly surface fires versus habitat types characterized mostly by severe, stand-replacing fires. However, in each case the fire parameter input is an estimate of the probability of a fire of some type (low or high severity) affecting an entire study area; this probability is assumed to have been constant throughout the reference period (e.g. the past 500 years).

Your Critique

Based on your knowledge of concepts and methods in the field of forest dynamics (including disturbance ecology) critically evaluate the FRCC procedure using the following cover types in Colorado:

1) ponderosa pine (including some Douglas-fir)

2) lodgepole pine

3) Engelmann spruce-subalpine fir

Note that I am not asking you to include the cover type known as “mixed conifer” in which Douglas-fir is dominant and associated with Abies spp, aspen, and/or lodgepole pine.

The overall goals of HFRA and the FRCC procedure could be criticized from socioeconomic and political perspectives (e.g. who should pay for fire hazard mitigation?), but those issues are beyond the scope of the exam. Instead, your objective should be to demonstrate your understanding of basic concepts taught in this course as they relate to the FRCC procedure. Some of the obvious concepts and issues to be considered are: ecosystem-based management, historic range of variability, traditional successional theory, modern framework for studying vegetation dynamics (i.e. the hierarchical patch dynamics non-equilibrium perspective), and the quantification of disturbance regimes.

Start your answer by first summarizing what is known about fire history and forest conditions of the past c. 400 years for each of these three forest cover types in Colorado. This should require less than two pages. Then, devote the remainder of your answer to a critical evaluation of the FRCC process to the ecological concepts emphasized in this course.

You do not need to give lengthy explanations of concepts. Instead, just comment on how the concept applies to or may have been neglected in the formulation of the HFRA goals and the FRCC protocol.