Lessons From the Fires of 2000: Post-Fire Heterogeneity in Ponderosa Pine Forests

We evaluate burn-severity patterns for six burns that occurred in the south- ern Rocky Mountains and the Colorado Plateau in 2000. We compare the results of two data sources: Burned Area Rehabilitations Teams (BAER) and a spatial burn- severity model derived from satellite imagery (the Normalized Burn Ratio; NBR). BAER maps tended to overestimate area of severe burns and underestimate area of moderate-severity burns relative to NBR maps. Low elevation and more southern ponderosa pine burns were predominantly understory burns, whereas burns at higher elevations and farther north had a greater component of high-severity burns. Thus, much, if not most, of the area covered by these burns appears to be consistent with historic burns and contributes to healthy functioning ecosystems. oncern that the size and severity of the 2000 fires were "beyond the range of natural variability" in ponderosa pine (Pinus ponderosa) and mixed conifer systems has provided justification for ecological restoration pro- grams. However, little is known about the spatial heterogeneity resulting from recent or pre-historic fires. Here we evaluate the effects of burn-severity pat- terns on landscape heterogeneity for burns that occurred in the southern Rocky Mountains and the Colorado Plateau in 2000. We compare the results of two data sources: Burned Area Rehabilitation Teams (BAER) and a spatial burn- severity model derived from satellite imagery. Burn-severity maps were developed using the Normalized Burn Ratio (NBR). NBR is derived from comparisons of pre- and post-fire Thematic Mapper im- agery (30 m resolution). Band 4 (near infrared) reflects changes in vegetation greenness and soil moisture, whereas band 7 (mid infrared) reflects soil type and moisture levels. Band 4 tends to decrease post-fire, whereas band 7 tends to increase post fire. NBR is based on the inverse relationship between bands 4 and 7: NBR = (band 4 - band 7)/(band 4 + 7). Delta NBR values are derived from differences in pre- and post-fire NBR scores, which in turn can be used as an index of burn severity (higher delta NBR indicates higher burn severity). The NBR methodology was developed to be repeatable and quanti- fiable, and it offers several advantages for quantifying burn severity compared to BAER maps, which are designed for rapid assessment and targeting of high-