Jen Costanza
Bio 255
10/14/05
Disturbance and the Historic Range of Variability
Summary:
The historic range of variability (HRV) concept is based on the idea that ecological systems are variable
in time, but that variability occurs within bounds. Quantifying the historic bounds of fluctuation for a
landscape can be useful to ecologists and managers. The HRV for an area can be instructive in placing a
current landscape in its temporal and spatial context, and can also be used as a tool to determine whether
current management actions or ecological processes are within the bounds experienced by the system
prior to extensive human impacts. Landres et al. (1999) discuss the benefits and utility of HRV concepts.
They state that the HRV for a landscape is often the only means we have to predict future impacts to
ecological systems. However, often determining the spatial and temporal extent to use in HRV analysis is
difficult. Landres et al. state that these are site-specific determinations that should be made according to
appropriate management goals for a site. Tinker et al. (2003) is a good example of one way to assess
HRV for a landscape. They construct a stand age map based on tree rings and fire scars for Yellowstone
National Park for 1985. They use it to construct maps of burned/unburned vegetation for 20-year intervals
since 1705, as well as similar maps for the nearby Targhee National Forest before and after clearcutting in
the late-20th century. Using landscape metrics, they show that the pattern generated by clearcutting in the
Targhee NF is outside the HRV created by natural fires in Yellowstone. In addition, the extensive fires of
1988 played a large role in determining landscape structure and HRV in Yellowstone. Thus, Tinker et
al.’s study is instructive because it shows current landscape patterns in a larger temporal and spatial
context, which should be useful to managers.
Required readings:
Landres, P. B., P. Morgan, and F. J. Swanson. 1999. Overview of the use of natural variability concepts in
managing ecological systems. Ecological Applications 9:1179-1188.
Tinker, D. B., W. H. Romme, and D. G. Despain. 2003. Historic range of variability in landscape
structure in subalpine forests of the Greater Yellowstone Area, USA. Landscape Ecology 18:427439.
Additional references:
Overviews of HRV and equilibrium concepts:
Landres, P. B. 1992. Temporal scale perspectives in managing biological diversity. Transactions of the
North American Wildlife and Natural Resources Conference 57:292-307.
Perry, G.L.W. 2002. Landscapes, space and equilibrium: shifting viewpoints. Progress in Physical
Geography 23:339-359.
Veblin, T. T. 2003. Historic range of variability of mountain forest ecosystems: concepts and
applications. The Forestry Chronicle 79:223-226.
White, P. S., J. Harrod, J. L. Walker, and A. Jentsch. 2000. Disturbance, scale and boundary in wilderness
management. Pages 27-42 in Wilderness science in a time of change conference, Vol 2:
Wilderness within the context of larger systems. US Department of Agriculture, Forest Service,
Missoula, MT.
Case studies:
Agee, J. K. 2003. Historical range of variability in eastern Cascades forests, Washington, USA.
Landscape Ecology 18:725-740.
Hessburg, J. F., J. K. Agee, and J. F. Franklin. 2005. Dry forests and wildland fires of the inland
Northwest USA: contrasting the landscape ecology of the pre-settlement and modern eras. Forest
Ecology and Management 211:117-139.
Kulakowski, D., and P. Bebi. 2004. Range of variability of unmanaged subalpine forests. Forum für
Wissen 2004:47-54.
Wimberly, M.C., T.A. Spies, C.J. Long and C. Whitlock. 2000. Simulating historical variability in the
amount of old forests in the Oregon Coast Range. Conservation Biology 14: 167-180