Much of our recent research has been located in the Rocky Mountains of Wyoming, particularly in Wilcox Fire, Graand Teton National Park, 2000and around Yellowstone National Park.  Large stand-replacing wildfires such as the 1988 Yellowstone fires create a very complex, fine-grained mosaic of lodgepole pine seedling densities across the burned landscape.  Our work here has examined the permanence of this landscape pattern given successional changes in stand structure across the landscape, which acts to compress the initial variability towards a common stand structure.  ThesePostfire stand changes in structural variability have direct influences on changes in landscape pattern, causing the landscape to become more coarse-grained as initially dissimilar stands coalesce into larger patches.  This work also highlights the natural occurrence of uneven-aged lodgepole pine stands and lends insight into potential silvicultural alternatives in these forests.

My initial work on stand structure has been carried further to examine how global change may affect carbon cycling at stand- and landscape scales. Figure from Kashian et al. 2013Understanding the how climate, disturbances, and stand structure affect carbon dynamics remains an important challenge in ecology, particularly as the frequency and severity of disturbances increases with climate change.  In Yellowstone, we asked how climate-mediated changes in fire Post-beetle killed standregimes alter the distribution of carbon budgets and thus the behavior of the entire Yellowstone landscape as a net sink or source of carbon in the global carbon cycle. In particular, we focused on net ecosystem production (NEP) – the difference between net primary production and heterotrophic respiration – and how it varies with stand structure and over succession.

We have recently completed a study funded by the Department of Energy’s National Institute for Climate Change Research that expanded the carbon/disturbance research to understand how bark beetle outbreaks affect forest carbon storage at stand and landscape scales. The Greater Yellowstone Ecosystem and most of the Rocky Mountain West is experiencing an extensive and intensive insect outbreak, such that insects including the mountain pine beetle (MPB) are an important driver of carbon dynamics and may determine whether western landscapes are carbon sinks or sources.  We developed a sister study to the post-fire study described above, examining chronosequences of forests that experienced MPB outbreaks of different severities.

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