Lee Frelich, Director of The University of Minnesota Center for Forest Ecology, is one of the foremost experts on the forests of the BWCAW and the fire ecology that dictates its composition. We interviewed him to gain his invaluable insight into this incredible ecosystem, its history, and a glimpse into its future.
Question 1. For the average person without a deep ecological perspective, the BWCA is just another beautiful place, but we know in looking at it that it’s an ecological marvel with a complicated patchwork of forest types, plants and animals interactions, and a complicated geologic, ecologic, and disturbance history. What’s your favorite part about studying the BWCA as an ecosystem? What parts fascinate you the most?
Lee Frelich: The response of the forest to landforms, soil chemistry (there are pH and nutrient gradients all over the place), human activity (e.g. native American burning of some parts of the landscape to favor red pine/blueberries, logging, fire exclusion) create a complex mosaic of forests. Also, the area has a unique climate in the 48 states, being further north and colder than northern Maine, and having a similar hardiness zone as Alaska. It is more boreal than indicated on most North American vegetation maps.
Question 2. There seem to be these two prevailing thoughts when it comes to the forests in the BWCA wilderness area in particular. One of these is that, other than the areas that have burned recently, it’s all this old-growth forest which to them often means huge pine stands. And it can be that whether it’s places like the Old Pines Trail, the old stands east of the Gunflint, the old stands along the Sioux Hustler, or even just individual ancient trees along the shore. The other prevailing thought is that the whole thing is second-growth forest that grew back after logging, and there’s plenty of that too. The BWCA as a fire-dependent ecosystem is a complicated mosaic. With that in mind, what makes this place special? What sets this wilderness area apart in the region?
Lee Frelich: About half of the forest was logged by European settlers, but the other half (375,000 acres) constitutes one of the largest remnants of unlogged forest in the eastern U.S. However, fires are common and normal, so young forests are part of the unlogged landscape. It’s not all old-growth as commonly defined, and due to site quality variation, some old growth actually has dwarf trees, in addition to the huge white and red pines that people think of as old growth. Fortunately, much of the logged area was logged during winter and the ground layer and its ecological legacy that goes back 1000s of years was not disturbed, so the second-growth forests have very good ecological legacies. Also, parts of the BWCAW (e.g. the border route) were frequently burned (by indigenous peoples) red pine stands, that were maintained with blueberries in the understory as one source of food, and as places to live. These stands were less likely to burn in wildfires because there was no understory of balsam fir, so the red pines probably lived longer there. However, most of the landscape was very large, even-aged stands of pines, black spruce, birch and aspen, due to the fire regime of infrequent very large fires. Note that there were always refuge areas from fire—lake shores, swamps with black ash, and rocky areas without fuel to perpetuate fire. Very old trees were always (and still are) present—e.g. white cedars 500+ years old, and a lot of old white pines along shorelines.
Question 3. In your years of studying this place, you must have run into things that completely overturned your previous understanding of how this place worked. What is something you have learned/discovered that changed the way you thought about this ecosystem?
Lee Frelich: The spatial patterns imposed by the landform (which really depends on rock formation) influence succession after fires, by determining where the remnant trees are—important for seeds of red and white pine, and also where late successional species like balsam fir and white cedar (both very flammable but with no adaptation to fire at all) have a refuge from fire, from which they can spread after a fire. The timing of succession from pine or birch and aspen depends on how far away a given forest is from these refuges.
Question 4: Part of a mosaic ecosystem is a patchwork of past disturbances from the small fires up to the landscape-altering ones. The big ones obviously stick in people’s minds. Miron Heinselman made note of two large, overlapping fires in 1863 and 1864 which were in all likelihood, substantially larger than any of our major fires these past 20 years. From our limited perspective, how do some of our more recent fires like Pagami, Ham, or Cavity compare with big fires of the past? How are the fires from the 1860s (or other fires in the 70s,80s, and 90s) still playing a role in the BWCA today some 150+ years later? As we look back 10-15 years at the more recent big fires, how can we expect these fires to continue leaving a legacy on this landscape 150 years from today?
Lee Frelich: Yes, the 1863-64 fires were huge, and also occurred in the western U.S. and elsewhere across North America. However, species like jack pine with serotinous cones can disperse their seeds after the fire, and the size of fires really does not affect regeneration species —what does affect that are other factors that I have mentioned. The recent fires are very similar to those of the past in terms of their size and proportions of the BWCAW burned per decade. We are now back to a fire regime similar to that before European settlement, after a period of very low fire occurrence from 1911 to about 1990 (during which balsam fir invaded many forests, making them more flammable and possibly leading to more intense fires in some areas). However, the Cavity Lake Fire was exceptionally severe because it was burning in blowdown from 1999, and all of these recent fires had some different effects because the climate is different now. The historic fires perpetuated mostly jack pine, red pine and white pine, and black spruce, with some boreal mixed wood (birch, aspen, black spruce and balsam fir mixtures). The recent fires are more likely to favor birch and aspen, with a lot less pine regeneration. This will be the legacy that is visible 100-150 years from now if the climate stays the same. With climate change, however, red maple and red oak are likely to invade, and even grasslands might occur in the western BWCAW.
Question 5: With major, landscape-altering disturbances like the ’99 blowdown or the 2016 blowdown, the forests can change suddenly and dramatically. How do these disturbances continue impacting the forests today? How have they changed the trajectory of this ecosystem? What major impacts will they continue to have down the road?
Lee Frelich: The 1999 blowdown caused very high-intensity fires (whether prescribed or wildfires), leading to the extermination of pines and replacement by aspen (spring fires) or paper birch (summer and fall fires). Conversion from conifers to deciduous boreal species is occurring in many places in the world’s boreal forests, including Alaska, northern Europe, and Russia. However, we have the largest and most intense blowdown (derechos) in the world, so the mechanism of conversion here is that conifers are flattened and then the fire consumes any conifer seedlings and seeds that are present. Birch and aspen can regenerate from stump or root sprouts, and their seed are spread for miles from the mother tree, so they can take over burned blowdown areas.
Question 6:. If you were to take a person who doesn’t have much to any understanding of ecology or this place and wanted to explain to them why the things you study are important, what would you say? Why is it important to understand the history of this place, the science, the function?
Lee Frelich: It is important to have natural areas to compare with areas managed for timber production, both unlogged and areas that were logged once. They are likely important for the maintenance of biodiversity, storing carbon, and showing the natural patterns of forest response to disturbance and climate that we will never see in commercial forest.