Ponderosa Pine: An Idaho ecosystem at risk
.
- L. F. Neuenschwander & Deirdre M. Dether:
- University of Idaho, Department of Forest Resources &
- USDA, Forest Service, Boise National Forest.
The stakes are high, time is short, and the method is generally misunderstood. But fire could literally save Idaho's forestlands.
The natural role of frequent, low intensity fire is to remove small trees,
recycle carbon, nutrients, and water, control shrubs, and maintain the
herbaceous understory with large tree overstory. However, due to past fire
exclusion activities, fuel profiles, shrubs, and small diameter trees have
increased in quantity and produced conditions for catastrophic, uncontrollable
conflagrations. Now the very ecological process that created the old growth
pine forests wildf reI is at risk.
Historically, natural fires were not lethal to large pine trees, since ponderosa pine, which dominated former Idaho forests, is naturally fire resistant. These fire adapted ecosystems were dynamically stable, resilient, and resistant to fire. However, the fire regime that exists today produces wildfires of increased size, intensity, severity, and uniformity. This unnatural trend of large, forest consuming wildfires in ponderosa pine stands was evident in Idaho s 1994 forest fires, and the trend will continue in future years, especially during hot, dry summers. After decades of fire suppression activities, today's fires are lethal to trees because they consume the crowns where life sustaining moisture is collected.
Ponderosa pine is an endangered ecosystem on the Boise National Forest. There, wildfire currently consumes relic ponderosa pine forests at an annual rate of five percent. This means that forest managers have no more than 22 years (until 2006 to 2017) to restore the current ponderosa pine ecosystem so that it can survive wildfire. If restoration is not accomplished within this short timeframe, Idahoans will find mature ponderosa pine standing only in isolated, fragmented locations.
The situation reflects declining biodiversity as well. Nearly 45 percent of the ponderosa pine forests on the Boise National Forest have already been converted to brush. After 2017, less than 20% of the historic ponderosa pine ecosystem will contain large, old trees old growth trees that an ecosystem needs to stay resilient and resistant to future catastrophic fire.
Is there hope? There is. In our state, fire was an ecological process and a fact of life for the normal, healthy pine forests of the past. To save our forests, we must return fire to its historic function in ponderosa pine ecosystems.
How can we do this' First, we must preserve the icons of our forests the oldest and largest trees, by fighting catastrophic wildfire with the gentler, more frequent, low intensity surface fires like those that used to wander through the woods before settlers began fire exclusion acitivities. While high intensity prescribed fires can kill large pines as well as wildfire, low intensity prescribed fires that simply mimick the historical fire regime can save a whole ecosystem.
Currently, Idaho's historical forests of open, park like pine groves continue to convert to a system of dense (and flammable) young tree undergrowth with a relic pine overstory. Fires change pine forests to shrub and even aged tree seedling systems, often dominated by the less fire resistant Douglas fir. The probability that these even aged forests will survive fire for the next 100 years is low, and when these areas reburn, fire kills the young trees and the ecosystem converts further to persistent shrubs. This new ecosystem will burn cyclically, remaining as a non forest. In the past, the shrub dominated ecosystem now replacing ponderosa pine was small. Now it is expanding, and will continue to grow as future fires consume more precious ponderosa pine.
Presently, the effects of the conversion of pine forest to brush are unknown and unpredictable. Many ponderosa pine forests adjoin streams, rivers, and lakes. As pine forests convert to shrub dominated ecosystems, Idaho nesting bird habitat, big game winter range, fish populations, and water quality will all be affected, and with unpredictable results. Local economies dependent on tourism, recreation, forestry, and grazing will also be impacted, and long term nitrification and sedimentation may affect water and power supplies to our communities.
As part of an ecosystem management strategy to restore forest health, the Boise National Forest and the University of Idaho formed a partnership agreement to develop a prototype landscape prescribed fire program. This ecosystem restoration began about two years ago using satellite imagery combined with Geographic Information System (GIS) analysis and modeling. Our analyses revealed the cause and rate of ecosystem conversion, the extent of potential catastrophic fire, probable numbers and locations of wildfires over 5,000 acres, and watersheds at highest risk from wildfire. We developed a sitespecific GIS model to suggest the priority and locations for prescribed spring fires within the highest risk watersheds. In the past, most spring burns have withstood the test of catastrophic wildfire and survived. Therefore, prescribed fires will at first be conducted in the spring to reduce fire intensity, impacts on watersheds, the quantity and duration of smoke, and the chance of uncontrolled burns.
In the spring of 1994, a 1000 acre prescribed spring burn was conducted at Cottonwood. Later that summer the most severe of Boise's 1994 wildfires, the 30,000 acre Star Gulch wildfire, blasted into the prescribed burn area. The prescribed burn treatment did not stop the inferno as the area reburned, but the wildfire dropped to the ground and most of the ponderosa pine trees within the Cottonwood burn survived. Outside the prescribed burn area, nearly all the trees were killed, including the oldest and largest pines, trees that had survived at least seven past wildfires.
The test fires and models for the landscape prescribed fire program will be evaluated this spring and summer, and we expect our spring prescription burn efforts to restore fire as an ecological process on the ponderosa pine ecosystem. The fire program will then be applied on the landscape level by 1996.
The stakes are high an inter ecosystem. The task is huge the Boise National Forest must conduct prescribed burns on at least 30,000 acres per year in order to restore and maintain its ponderosa pine forests. And time is short less than 22 years. However, the analyses and models are ready for implementation. We know why, where, when, what ti';neframe, and how to employ landscape prescribed fire to save the ponderosa pine ecosystem. We know the consequences of no action, of current management action, and of not applying landscape prescribed fire. There is still hope if we act now.
END
