Mountain meadows comprise a small portion of the largely forested western Cascade landscape, but serve many important ecological and societal functions. However, decades of fire suppression and changes in climate and/or grazing pressure have led to recent (and often dramatic) expansion of forest into meadow. Faced by gradual loss of these habitats, federal land managers have begun to experiment with prescribed fire as a potential tool for restoration. With funding from the Joint Fire Science Program we have initiated studies at Bunchgrass Ridge to improve our understanding of the ecology and dynamics of montane meadows and to guide strategies for their restoration and maintenance (click to see full proposal).
Bunchgrass Ridge forms a gently sloping plateau at ~4300 ft elevation in the western Cascade Range, adjacent to the Mt. Washington Wilderness. It was designated a Special Habitat Area in the 1990 Willamette NF Land and Resource Management Plan and was identified as a high-priority restoration project during the 1995 Upper McKenzie Watershed Analysis. Because it supports a large mosaic of meadow and forests of varying age, it provides an ideal setting for studying the process of conifer encroachment and for experimenting with restoration. Several studies are in progress:
1. Spatial and temporal patterns of conifer encroachment and associated changes in ground-layer vegetation. This research provides the historical and ecological context for subsequent studies that address the potential for restoration. In four 1-hectare (100 x 100 m) plots all trees >1.4 m tall have been spatially mapped, measured for diameter, and aged (from increment cores or basal sections). Detailed measurements of understory composition were taken in 10 x 10 m subplots within each plot. A composite age structure reveals two periods of forest expansion at Bunchgrass: a broad window of establishment between 1815 and 1905, and more recent and massive recruitment between 1925 and 1985. During both periods, establishment of lodgepole pine preceded that of grand fir - a pattern that is clearly evident in the spatial clumping of grand fir around live and dead lodgepole pine. Ongoing work explores in detail the spatial and temporal patterns of encroachment and changes in ground-layer vegetation as open meadow is replaced by forest.
2. Composition and dynamics of the soil seed bank and its potential role in meadow restoration. A second study explores the below-ground dynamics of this system. It poses the question: Does the composition of the soil seed bank change as meadows are replaced by forest, and by implication, can the seed bank serve as a source of propagules for meadow species if trees are removed or sites are burned? Soil samples were extracted from >200 subplots representing a gradient from open meadow to old forest. Samples were spread in germination flats in the greenhouse and seedling emergence has been monitored. A total of 47 taxa have been identified (compared with >130 species in the above-ground flora). Most germinants were early successional species, although the dominant sedge at Bunchgrass, Carex pensylvanica, was also well represented in the seed bank. Future analyses will explore relationships between seed bank composition and forest age, structure, and understory composition.
3. Vegetation responses to experimental restoration treatments. We are in the initial stages of a large, replicated experiment that examines vegetation responses to restoration treatments. Three replicates of each of three treatments will be applied to a total of nine 1-ha plots. Treatments include a control, complete overstory removal, and complete overstory removal plus prescribed burning of residual slash. These comparisons will allow us to test whether fire is necessary to achieve restoration goals or whether removal of the overstory is sufficient. Pre-treatment sampling of overstory structure and understory composition was completed in 2004.
We have designed these studies to yield useful short-term products for scientists, managers, and the public, and to provide opportunities for long-term research and education. Participants include faculty and students from the University of Washington, Oregon State University, and University of Victoria, scientists from the USFS-PNW/Andrews LTER, and land managers from the USFS McKenzie River District. Our goal is to develop an ecological basis for restoration of meadows in the western Cascades, using Bunchgrass Ridge as a center for research, adaptive management, and outreach. For more information see: http://faculty.washington.edu/chalpern/Bunchgrass.htm