This third report in the FMF Natural Disturbance Program research series looks at fire patterns within riparian zones at four different scales using three different sets of data and methods. The report is essentially an integrated synthesis of all or parts of four separate research projects under the auspices of the FMF Natural Disturbance Program. Specifically, we looked at whether, or to what degree, burning patterns in riparian zones differ from that of the landscape as a whole. Other research has found evidence of differential fire behaviour in other ecological areas, and our summaries suggest that riparian areas are unique terrestrial habitat in terms of species composition, relative tree density, topographic position, and eco-site type.

We found that riparian zones positively influence the chances of survival from fire at very fine scales. Although there is no evidence of either the age-class distribution, or percentage of old forest of riparian zones differing from the rest of the landscape at very coarse scales, we did find evidence that small, partially burnt residual islands tend to form at or near riparian zones more often than expected. Such islands tend to survive the fires relatively intact, form at wide streams and on wetter sites, and chances are very high that the surviving trees will be white spruce. We also found evidence that fires tend to stop at riparian zones more than expected, and particularly so on large streams with steep slopes.

However, in all cases, the relationships are weak, and highly variable. All of our data demonstrates that fire burnt through the vast majority of the riparian zones we studied, and the majority of island remnants occur nowhere near riparian zones. Furthermore, the high variation in the results suggests that the most likely source of variation in fire behaviour is local fire weather. In other words, the chances of a given riparian zone surviving or coinciding with the edge of sequential fire events are extremely small on our study area.

We also found evidence to suggest that fire in riparian zones is at least partially responsible for the unique habitat characteristics of riparian zones. Field data demonstrated that some riparian zones experience steady ingrowth of tree species for many decades after a fire. Presumably fire “cleans” these sites when it burns through.

In summary, although we found considerable corroborating evidence to suggest that riparian zones burn somewhat differently than upland parts of the landscape, the fact that fire is an integral part of riparian ecosystems is inescapable. The removal or prevention of disturbances from these habitats would presumably have significant ecological consequences. On the other hand, the introduction of cultural disturbance techniques comes with many ecological pitfalls as well. The information in this report will hopefully help guide us through this dilemma by providing a foundation of understanding of the terrestrial side of fire in riparian areas. iii