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Special Session: California and Australian Aboriginal Burning Practices and Contemporary Fire Management: Restoration of culturally significant habitats. Frank K. Lake FLOOD TRUMPS CULTURAL PRESCRIBED FIRE: DISTURBANCE EFFECTS ON
WILLOW COMMUNITY STRUCTURE COMPOSITION AND FUEL LOAD
Frank K. Lake USDA Forest Service, PSW Arcata, California. 95521 INTRODUCTION
Originally, the goal of this study was to examine fire’s potential in rejuvenating stands of sandbar willow (Salix exigua) after many years without flooding disturbance. Ironically, after the prescribed fire was implemented in October 2005, flooding in early January 2006 would complicate evidence of fire’s effects on willows. Flooding historically scoured and redistributed willows, causing regrowth that the Native American basket weavers relied upon for basket material. Based on discussions with Karuk basket weavers and elders in the time periods between flooding disturbance, Native American basket weavers likely burnt willows to reduce insect pests and stimulate resprouting for useable shoots. In the absence of flooding of sufficient magnitude, burning would have been used between major flooding events. Historically, if a flood occurred the winter following a fall burn, the disturbances created similar effects to vegetation, but not necessary in the fuel load or geomorphology of the riparian zone. This project’s objectives were burn three geographically separate sandbar willows patches along the mid-lower Klamath River in northern California and research changes in the composition, structure, and density of shrubs, forbs, grasses, and fuel load. In the case of my prescribe fire research, flooding compounded the ability to discern fire effects for the study. The methodology selected to study the effects of fire, and subsequent flooding, on sandbar willow communities was modified from FIREMON fire effects monitoring protocol (www.fire.org). Vegetation consisting of young trees, shrubs, forbs and grasses were surveyed pre and post disturbance according to FIREMON DENSITY (DE) belt transects with quadrats sampling procedures. Along belt transects each individual shrubs stem emerging at within 5 cm of ground level was counted with sums per transect per site tallied. Individual shrub stems were counted per size class (small to very tall) and status (live or dead). Transect counts for sandbar willows are presented without analysis. Further analysis needs to be conducted. Quadrats were systematically spaced 5 meters apart along transects. In each 1-meter square quadrat pre and post vegetation and substrate was sampled. Substrate composition cover was estimated, then for all possible discernable forb and grass species the number of individual units, stems or clumps emerging at ground surface level, were tallied and percent cover visually estimated for each species per quadrat. Data collection was conducted during the early summer months of June-July, when foliage and flowering facilitated species identification and determination of Status. Native and exotic forb and grass species were determined at time of surveys or following sampling with the use of field guides or botanist. Quadrat vegetation data are was analyized using SAS (v. 9.1) Proc Mixed, Random/Repeated comparing the percent cover totals for species and cover type. Analysis of native and exotic species affected by the treatment is not presented. A modified FIREMON Fuel Load sampling methodology was used to survey the amount of live and dead fuel along seven transects at each site, including fuel load counts for 1, 10, 100, 1000 hour (sound and rotten) fuel classes, and vegetation live/dead cover and duff/litter depth at two plots per transect. Summary data from FIREMON FL program calculations is presented. The sandbar willow shrub count summaries (counts per belt transect totaled per site for size class and status: live or dead) for one of the three sites affected by fire and flooding is presented here. Below are the preliminary data results for the Big Bar willow site: T 10N, R 5E, Section 17 41° 15’09.32” N, 123°38’09.67” W, elevation 318 feet, along the mid-lower Klamath River, between the town of Orleans and Weitchpec. Big Bar Willows 2004 to 2006
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Quadrat data for the Big Bar site pre and post prescribed fire/flooding:
Type 3 Test of Fixed Effects for forbs, grasses and substrates found significant: Cover Name
Effect Num
Den F-Val.
White Sweet Clover Exotic treatment 1 78
Fuel load changes for the Big Bar willow site:
Location w/
Treatment
Location
w/
Treatment
DISCUSSION
Fire effected the vegetation of sandbar willow communities similarly to flooding but there were several important distinctions in how fire was different than flooding in affecting the composition, structure, and density of shrubs, forbs, grasses, native/exotic species and fuel load present. Fire effected the composition of riparian vegetation, similar to flooding, by reducing cover and/or density of shrub, forb, grass and fuel. Fire modified biological and physical conditions which facilitated changes in habitat micro sites to the benefit/detriment of some plant species. Fuel that was susceptible to combustion at time of prescribed fire was generally reduced. Flooding can deposit whole, parts, or seeds of shrubs, forbs, grasses, and organics as fuel from up-stream to new downstream locations, modifying the future potential composition and structure if those migrants become established. Flooding, as observed in this study, reduced the composition (type) and amounts of different types of fuel present in a willow patch by flushing away, or by depositing fuel. Following prescribed fire, flooding was observed to flush away partially or unburnt litter, duff , 1, 10, 100, 1000 hours fuels, in addition to abrasively damaging live fuel, which created future dead vegetative fuel. Flooding also deposited organic debris of all compositions: needles, leaves, roots, branches, trunks, and whole plants, which recruited potential fuel for subsequent fire events. At the Big Bar site deposited flood debris substantially increased the fuel load. Fire affected the structure of vegetation by modifying (reducing) the density of older mature larger willow and shrubs species, and simulated (recruits) the rejuvenation of younger vegetative regrowth or seedlings. Flooding effects the structure of vegetation by modifying (reducing) the density of older mature larger willow and shrubs species if scoured and flushed away (export), or predominately pushes over mature taller shrubs, and simulates (recruits) the rejuvenation of younger vegetative regrowth off the main trunks or branches. Fire did little to modify the geomorphic condition of sandbar willow communities. In comparison flooding can substantially redistribute and modify the geomorphic composition and arrangement of substrates and local surface topography (structure). CONCLUSION
Preliminary research findings demonstrate that prescribe fire effects coupled with flooding activity can substantially modify the distribution (composition), abundance (density), and arrangement (structure) of shrubs, forbs, grasses, and fuel. Flood trumps fire in the duration and intensity of disturbance effects on sandbar willow patches studied. Fire affected willow patches for minutes to hours under low to moderated intensity burning, where as flooding affected willow patches for hours to days of inundation at low, moderate to high intensity with variable water velocities. LITERATURE CITED
FIREMON. 2005. Version 2.1.1. Density and Fuel Load methods, Final Draft. www.fire.org. SAS Version 9.1. 2005. SAS Institute Inc. Cary, NC, USA

Source: ftp://ftp.nofc.cfs.nrcan.gc.ca/pub/fire/Alexander/2006_San_Diego_Conf/Extended%20Abstracts%20PDf%20Files/Special%20Session/1%20Lake/lake.pdf