Abstract: We adopted the concept of fire regime departure used by Schmidt et al. (2002) and later refined by an interagency group of scientists (http://www.frcc.gov). Deriving condition class entails comparing current conditions to some estimate of the historical range that existed prior to substantial settlement by Euro-Americans. The departure of the current condition from the historical base line serves as a proxy to the potential of severe fire effects. In applying the condition class concept, we assume that historical fire regimes represent the conditions under which the ecosystem components within fire-adapted ecosystems evolved and have been maintained over time (Hardy and others 1998). Thus, if we projected that fire intervals and/or fire severity has changed from the historical conditions, we would expect that fire size, intensity, and burn patterns would also be subsequently altered if a fire occurred. Furthermore, we assumed that if these basic fire characteristics have changed, then it is likely that there would be subsequent effects to those ecosystem components that had adapted to the historical fire regimes. As used in this paper, the potential of severe fire effects reflects the probability that key ecosystem components may be lost should a fire occur. Furthermore, a key ecosystem component can represent virtually any attribute of an ecosystem (e.g., soil productivity, water quality, floral and faunal species, large-diameter trees, snags, etc.). We used three classes of fire regime condition class to qualitatively rank the potential of severe fire effects to key ecosystem components (Table 17). We assessed the transition between our projected current fire severity and the historical fire regime of a given site to derive condition class. In addition, we evaluated the existence of fire-intolerant species in respect to that which would be expected under the native disturbance regime. If the evidence suggested that fire severity had changed by at least one class, then we would conclude that the condition class had a value exceeding Class 1. In other words, we would infer that the fire effects would be something other than the effects expected under HRV if the structure and composition of the vegetation did not reflect the historical range of conditions. The greater the departure, the greater the probability that key components would be lost if a wildfire occurred. We did not assign a value for condition class to cover types that would not likely experience wildland fire (for example, agriculture, urban, water, rock/barren). Local experts from the BLM derived our rule sets for non-forested settings. The following assumptions were used to develop the modeling rules for deriving fire regime condition class: 1. The current fire severity, and consequently the condition class could only increase as a result of fire exclusion; 2. Condition Class 1 occurred if there had been no detectable change in fire severity between the historical fire regime and the current fire severity and where there is no evidence that suggested that the vegetation structure or composition had changed from that which would be expected under a native disturbance regime. 3. Cover types indicating a dominance of fire-intolerant species should not occur where HFR = NL. 4. Dense stands of fire-intolerant cover types would not be expected naturally where HFR = MS1 or MS2. 5. Although fire exclusion has likely resulted in an increase of the duff depth, and consequently future fires will probably be more severe, the resolution of our base data did not allow us to make inferences concerning duff depths. 6. Fire exclusion has not measurably changed fire severity of those communities within the MS3, SR1, and SR2 fire regimes. This lack of change is more of a reflection of the resolution of our base data than it is of actual ground conditions. The attributes representing stand structure and composition in our database were not refined enough to estimate changes in such attributes as duff depth. 7. Vegetation composition and structure has changed substantially in those PVTs in which white pine or white-bark pine were major seral components (e.g., TSHE, THPL1, THPL2, ABLA4, PIAL, LALY) due to white-pine blister rust, as well as past timber harvest practices. Fire regime condition class in these sites was assumed to have a moderate or significant departure based upon the canopy cover of shade-tolerant species.
Purpose: These data were designed to characterize the mid-scale patterns of fire regime condition class across the state of Idaho. They were developed to help assess the risks of wildland fire to ecosystems at regional and subregional scales. GENERAL LIMITATIONS These data were designed to characterize mid-scale patterns across the state of Idaho at a scale of approximately 1:100,000. The use of these data at scales less than 1:100,000 is not recommended without field verification. Although the resolution of this theme is a 90-m cell, the expected accuracy does not warrant its use for geographic extents smaller than approximately 10,000 acres. That is, these data were not designed to be used for "project level" assessments that typically require 1:24,000 scale data.

Progress: Complete
Update Frequency: Unknown

Theme Keywords: ESRI Geography Network Thesaurus, environment
Place Keywords: Idaho

Access Constraints: Public, Tribal Enterprises, Tribal Government, Individual Authorized Users
Usage Constraints: These data were designed to characterize mid-scale patterns across the state of Idaho at a scale of approximately 1:100,000. The use of these data at scales less than 1:100,000 is not recommended without field verification. This data set is provided "as-is" without warranty of any kind, including, but not limited to, the implied warranties of merchantability and fitness or a particular purpose. The user assumes all responsibility for the accuracy and suitability of this dataset for a specific application. In no event will the creators or USDA Forest Service be liable for any damages, including lost profits, lost savings, or other incidental or consequential damages arising from the use of or inability to use this data set. Use of these data may require the ability to read ArcInfo Grid datasets. Although the resolution of this theme is a 90-m cell, the expected accuracy does not warrant its use for geographic extents smaller than approximately 10,000 acres. That is, these data were not designed to be used for "project level" assessments that typically require 1:24,000 scale data.