Ecological and Cultural Significance of Burning Beargrass Habitat on the Olympic Peninsula, Washington
Daniela Joy Shebitz, Sarah Hay den Reichard and Peter W Dunwiddie. 2009. Ecological and Cultural Significance of Burning Beargrass Habitat on the Olympic Peninsula, Washington. Ecological Restoration Vol, 27. No. 3, 2009.
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ABSTRACT
To conserve or restore culturally significant plants, one must consider the important role that indigenous land management techniques have played in maintaining habitats of those species. Beargrass (Xerophyllum tenax) is a basketry plant used by Native Americans and is reportedly declining in traditional gathering sites. Many low-elevation beargrass sites on the Olympic Peninsula in Washington were maintained as savannas and wetland prairies through anthropogenic burning prior to European settlement. This study measures short-term (1 and 2 y) effects of reintroducing prescribed burning (both low and high severity) and manual clearing on beargrass growth and reproductive success—flowering, vegetative reproduction, and seedling establishment. High-severity fire led to a significant increase in beargrass seedling establishment and vegetative reproduction over two years but a decline in beargrass cover. Low-severity fire also decreased beargrass cover, but did not significantly affect shoot production or seedling establishment. In areas where vegetation and coarse woody debris were manually cleared, beargrass cover decreased, while shoot production and flowering increased. Neither low-severity fires nor clearing plots affected beargrass seedling establishment. Results indicate that fire is a useful tool for enhancing low-elevation beargrass populations in this region.
Introduction
The persistence of many indigenous traditions is dependent upon the availability of culturally significant resources {Anderson 1996a, 1996b, 2005). Baskets made from local plants, for example, strengthen cultures by preserving traditions, reinforcing communities, and providing income (Shebitz and Kimmerer 2005). Indigenous basketmakers throughout the United States, however, have reported a decline in abundance and quality of basketry plant material at historic gathering sites. The absence of traditional burning over the past century is a potential cause for the decline in abundance of some basketry plant species, including deergrass (Muhlenbergia rigens) (Anderson 1996b), sweetgrass (Anthoxanthum nitem [=Hierochloe odorata]) (Shebitz and Kimmerer 2004), and beargrass (Xerophyllum tenax) (Hunter 1988, Rentz 2003, Shebitz 2005).
To conserve or restore culturally significant plants, it is often necessary to restore land management techniques that formerly maintained habitats of those species. Prior to European contact, Native Americans played a complex role in shaping landscapes through activities such as burning and harvesting that were regular and long term (Lewis 1993, Stewart 2002, Anderson 2005). These practices often substantially altered the composition and structure of plant associations and influenced species distributions (Anderson 1996a, 2003). Management practices also led to the establishment of vegetation communities in locations where they would not otherwise have existed (Boyd 1999). For example, despite the high precipitation and low natural fire frequency in western Washington, prairies and savannas were dominant components of the Puget Sound Lowland landscape for millennia prior to European settlement due to anthropogenic management (Norton 1979, Lewis and Ferguson 1999, Peter and Shebitz 2006). Indeed, anthropogenic fire was the most important tool of environmental manipulation throughout the Pacific Northwest (Boyd 1999).
Anthropogenically Maintained Beargrass Habitat in the Pacific Northwest
Native Americans of the southeastern and western Olympic Peninsula of Washington have a long history of managing the landscape to ensure the availability and quality of desired plant species (Regan 1934, Norton 1979, Boyd 1999). Beargrass (Figure 1) is one example of a culturally significant plant commonly harvested from the Olympic Peninsula lowlands for use in basketry by tribes such as the Quinault and Skokomish (Günther 1981, Nordquist and Nordquist 1983, James and Ghubby 2002). Prior to Euro-American settlement, low elevation sites where beargrass was gathered were maintained as savannas and wetland prairies through anthropogenic burning (Jones 1936, Peter and Shebitz 2006). Due to the exclusion of both anthropogenic and natural fires since the 1850s, most of these formerly open areas are now covered with dense Douglas-fir (Pseudotsuga menziesii) (Norton 1979, Boyd 1999, Peter and Shebitz 2006).
Beargrass is believed to have declined in traditional gathering sites over the past few decades in part due to forest encroachment resulting from the absence of fire. In fact, a study by Shebitz and colleagues (2008) found a significant decline in beargrass abundance in the southeastern Olympic Peninsula since 1986.
Low-severity burns have long been used by Native Americans throughout the western United States to enhance the growth of beargrass and provide basketry material (Hunter 1988, LaLande and PuUen 1999, Rentz 2003, Shebitz 2005). In addition to Olympic Peninsula tribes, the Yurok, Karuk, Hupa, Ghilula, Upland Takelma, and others burned beargrass periodically and then harvested leaves from the burned clumps one to three years later (LaLande and Pullen 1999, Rentz 2003, Anderson 2005).
Historically, burns were low-severity, slow-moving surface fires (Lewis 1993, Hunter 1988, Rentz 2003) that burned old beargrass growth and up to 95 percent of living foliage (Hunter 1988). According to Skokomish oral tradition, on the southeastern Olympic Peninsula, lowland prairies were burned at 2—3 year intervals to maintain a diversity of edible and textile plants and to sustain suitable habitat with a relatively open canopy (Peter and Shebitz 2006). Beargrass generally was in the savanna-like periphery of prairies, occurring with some canopy cover. According to interviews with Skokomish and Quinault elders, this beargrass habitat was often not the target of the burns but was affected when a prescribed fire’s boundaries were extended because of environmental conditions such as wind. The primary reason for the burns was generally to manage land for game such as blacktail deer (Odocoileus hemionus columhianus) and Roosevelt elk (Cervus elaphus roosevelti) in an otherwise forested landscape. A secondary reason was to maintain food plants such as camas (Camassia quamash var. azurea). Camas was traditionally a fundamental food crop for western Washington tribes (Günther 1981), and maintaining an open habitat for camas was a primary reason for burning in the Pacific Northwest (Boyd 1999). …
Objectives and Predictions
This study was undertaken to determine if prescribed burning would help reverse the observed declines in the abundance of low-elevation beargrass. We predicted that burning would result in increased vegetative reproduction, growth, flowering rates, and seedling establishment. In addition, we compared the effects observed following fire with a manual treatment, since reintroducing burning might not be possible in some instances. Treatments were applied in the autumn, the same time of year that Native Americans historically burned the area (Peter and Shebitz 2006). By examining the effects of fire and manual clearing of vegetation separately, we can assess the extent to with competition from understory species is influencing beargrass growth and reproduction. We set up four experiments to examine different aspects of this hypothesis (Table I). …
Discussion
The research presented in Experiments 1 and 2 serves as a case study to investigate the effects of a high-severity fire on beargrass reproduction. The scope of inference was limited by the absence of replicate sites and the fact that the response data are limited to one or two years (for Experiments 1-2 and 3-4, respectively) following the treatments. …
Beargrass plants in low-severity burn plots had significantly lower leaf length, height, percent cover,
and crown area than those in reference plots. Beargrass in cleared plots, however, was not significantly different from that in the reference plots. We believe that this finding suggests that the postfire recovery period for beargrass was longer than the recovery period after manual leaf cutting. The length of recovery for burned plants is dictated by the meristem damage; if severe, a plant may not recover. …
Findings from Experiment 3 emphasize the importance of competition in beargrass vegetative reproduction. Research on high-elevation beargrass in Idaho found that the species can be very sensitive to competition from shrubs following disturbance (Laursen 1984). It is possible that at Skokomish, the decrease in shrubs as a result of fire was more influential than the fire itself in the increase of beargrass. In Experiment 3, only manually cleared plots had a significant increase in beargrass shoots compared to the reference plots. A significant difference in beargrass vegetative reproduction may occur between the burn and reference plots after an additional year or two, yet much of the success of beargrass reproduction will depend on competition from shrubs. …
Despite previous observations of high-elevation beargrass flowering within the first year following fire (Kruckeberg 2003), we found no significant effect of a high-severity burn on flowering one or two years after burning and a decline in flowering after a low-severity burn. Maules (1950) emphasis on soil temperature in controlling flowering rates leads us to hypothesize that the relative increase in soil temperature is greater after a fire in subalpine prairies than in the warmer low elevations, and therefore has a greater effect on beargrass flowering. …
Our research suggests that high-severity, but not low-severity, fires are effective at preparing safe sites for beargrass seedling establishment. …
We believe that the most important factor influencing beargrass survival was its micro-topographical position within the site. Microsites that are generally seasonally flooded and permanently saturated (Kulzer et al. 2001) characterize the bog. In 2005, these lower microsites were flooded throughout the year, including during the summer, despite the fact that 2004-2005 received less precipitation than average (WRCC 2005). Hummocks up to 1 m long occur throughout the site; they generally consist of well-drained soils, and are therefore typically drier. The higher number of beargrass shoots on hummocks compared with the number observed between hummocks supports the hypothesis that beargrass survival at this site was linked mostly to its occurrence in dry microsites in an otherwise flooded landscape. …
An interesting paradox is that, while historically burns set by indigenous people in the Pacific Northwest were likely low-severity surface fires, in this study it was the high-severity fire that resulted in an increase in beargrass vegetative reproduction and seedling establishment. Perhaps this finding is due to environmental changes, such as the accumulation of biomass and altered hydrology, that have occurred in the absence of fire. …
Conclusions
… This research illustrates the importance of incorporating traditional land management techniques such as burning practices in ecosystem restoration. While methods focused on beargrass, this research serves as a case study for examining implications of reintroducing burning to a historically maintained vegetative community and resource. In addition to the species-specific effects of increasing beargrass vegetative reproduction and seeding establishment rates, restoring fire to anthropogenically maintained landscapes on the Olympic Peninsula has significant ecological and cultural implications. Reintroducing anthropogenic burning to maintain savannas and wetlands reestablishes an ecosystem component that is now absent from this area. Restoring low-elevation savannas and prairies through regular burning may support flora and fauna communities that have depended on these habitats for millennia. …
