Regenerating Forests

Nothing Succeeds like Succession

The great fires of 1988 in Yellowstone National Park became international news, sparking debate about fires’ beneficial role to nature versus its detriment and cost to society. At YERC, we’ve focused on the science, examining the long-term ecological responses to this grand-daddy natural experiment (although the fire in 1700 was much larger and hotter!). For example, our forest succession models project that the upcoming decades may bode well for snowshoe hare habitat, which in turn may hasten an increase in Canada lynx populations. Among our accomplishments of this ongoing research program are several that have not been previously achieved. We utilized NASA technology and collected massive amounts of field data to map the density of tree saplings (tens of millions) that regenerated after the 1988 fire.

We took a similar approach to map and validate the type and volume of coarse woody debris or CWD (standing snags and downed logs) across an area twice the size of Yellowstone National Park. This kind of information is vital to the agencies that are mandated to set aside CWD for use by cavity-nesting birds and hundreds of smaller animals. YERC is now hoping to begin analysis of our long-term datasets to learn what environmental factors ‘control’ the survival of new saplings that are now nearly 30 years old. We have also begun investigating how forests regenerate after fires and how it affects carbon fluxes and their contributions to global warning. In a recent paper, we collaborated again with NASA and built a model to examine just that. What we discovered is that the expected contribution of carbon to the atmosphere from decomposition may be occurring over a century or more versus the decades that were expected.

Forest succession model simulations showing long-term vegetation dynamics on a moist upland site in Yellowstone National Park starting from a near-bare earth initial condition for a grid cell (45.5 S, 109.5 W). Lines show changing above-ground biomass (KgC m-2) of the different plant functional types (black = total biomass, green = early successional broad-leaved tree (e.g., aspen), pink = mid- successional evergreen tree (e.g., lodgepole pine), purple = late successional evergreen tree (e.g., douglas fir). We are working with the National Science Foundation’s new program called NEON (National Ecological Observatory Network) to incorporate high-resolution remote sensing data to accurately classify these forest species thereby greatly enhancing the accuracy of model output (carbon flux, biomass, productivity, etc.).

With more support for fieldwork and analysis, we can unravel the mysteries and mechanisms responsible for these phenomena and learn from a grand experiment at ecosystem scales. The smoke is clearing and the lessons of the great fire of 1988 are now beginning to show themselves decades later. But we expect that more research and monitoring over a 50-year period is still needed. And that’s our goal.

Two images. One taken during the great Yellowstone fires of 1988 and the other is a NASA satellite image taken during the summer of 1989 with still visible burned areas (reddish color). What you don’t see are millions and millions of lodgepole pine seedlings that established themselves immediately after the fire.