The effects of mastication and prescribed fire on medusahead (Taeniatherum caput‐
medusae) cover and frequency Michelle Coppoletta, Sierra Cascade Ecology Program 30 March 2012 Over the past 20 years, managers of public lands in the western United States have witnessed an explosive spread of medusahead (Taeniatherum caput‐medusae). This highly invasive grass is able to grow in a wide range of climatic conditions and has been documented in plant communities up to 7,000 feet in elevation. Medusahead is a species of significant concern on the Plumas NF because it occurs in relatively disturbed areas, such as roadsides and railroad tracks, where there is elevated risk of spread into un‐invaded native plant communities. Even more problematic, is the fact that Figure 1. Medusahead inflorescences.
most traditional treatment methods, such as manual removal, biological control, and chemical treatment are either impractical or ineffective. Studies that have investigated the use of prescribed fire to control medusahead have produced variable results. A number of studies have demonstrated that burning medusahead in late spring, prior to seed dispersal can significantly reduce infestations (Rice 2005). In contrast, prescribed burns initiated in the summer and fall, have not been effective due to the fact that the seeds have been dispersed and are on or above the soil where they are protected from the heat of the fire (Kan and Pollak 2000). Over the past six years, Plumas NF botanists have been testing a relatively new method of medusahead control: flaming with a propane torch. Results from these trials have demonstrated that spring flaming of small infestations can reduce the percent cover of medusahead by an average of 95 percent (Coppoletta 2006). The major limitation with this method is that it is extremely time intensive and is not considered practical or feasible for control of large medusahead infestations; however, these results do suggest that high intensity fire (such as that achieved with flaming) applied prior to seed set, could be an effective method of control for medusahead. On the Plumas NF, mastication is one method that is commonly used to mechanically treat small diameter trees and shrubs for fuel reduction. This treatment utilizes machinery to break up or “chew” live and standing biomass and convert them into surface fuels. In 2010, botanists on the Plumas NF targeted a large medusahead infestation within a proposed mastication unit, to answer the following questions: 1. Does the frequency and percent cover of medusahead change in response to mastication and prescribed fire treatments? 2. If so, is this change associated with (a) reduced shrub and tree cover or (b) masticated fuel loadings? METHODS Field Sampling Eighteen permanent monitoring transects were established in June of 2010 to evaluate the effect of mastication and prescribed fire on medusahead cover and frequency. Thirteen transects were established within the proposed treatment unit and five were established in an adjacent area where treatments will be excluded. The following data were collected along each transect before and after treatment: 
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Frequency: Presence and absence of medusahead was recorded within a nested quadrat at five points along each transect. The size of the frequency quadrats were: (1) 10 x 10 cm; (2) 20 x 20 cm; and (3) 50 x 50 cm. Cover: Percent cover of medusahead, shrubs, and trees was estimated (using cover classes) within five 1m2 quadrats placed along each transect. Fuels: surface fuel measurements were collected after mastication treatments using the planar intercept (Brown’s transect) method along each medusahead transect. Fine (0‐3”) woody debris was tallied, course (>3”) woody debris was tallied and measured, depth/litter depth was measured, and percent slope recorded. Mastication treatments occurred in the summer of 2010; landscape level changes can be seen in the photographs below (Figure 2). Figure 2. Monitoring transect before (left) and after (right) mastication treatment. Data Analysis One‐way analysis of variance (ANOVA) was conducted to compare changes in medusahead frequency, medusahead cover, and shrub cover within the treatment unit and the control. Simple linear regression was used to evaluate the relationship between medusahead cover and overstory shrubs. Surface and ground fuel loads were calculated using equations developed for California forests (van Wagtendonk, et al. 1996). Descriptive statistics of surface and ground fuels by size class were calculated and used to compare with published fuel load estimates from other masticated areas within California (i.e. Kane et al. 2004). RESULTS Prior to treatment, the percent cover of medusahead in plots was negatively correlated with the amount of overstory shrub cover (p=0.0002, α= 0.05); plots with high shrub cover had lower medusahead cover. As expected, mastication treatments resulted in a significant decline (p = <0.0001; α= 0.05) in shrub cover. Within the treatment unit, shrub cover dropped from an average of 35 percent to just over one percent cover following treatment. Despite this decrease in shrub cover, there was no significant change in medusahead frequency or percent cover one year after treatment (Figure 3). 2010
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Figure 3. Change in medusahead and shrub cover within treated and untreated plots. Error bars represent the standard error (SE). Other studies (i.e. Wagner et al. 2001, Young and Evans 1970) have observed time lags in medusahead invasion immediately following shrub removal; these delays are generally attributed to the presence of perennial grasses, which can initially suppress medusahead invasion. In our study, the potential lag in response is most likely due to the quantity of ground and surface fuels within the treatment unit, which may suppress medusahead germination or inhibit dispersal to areas of newly created suitable habitat. Calculated post‐treatment estimates of fuel loading for woody fuels within the treatment unit and control are presented below in Table 1 and displayed in Figure 4. There was no significant difference between the treated unit or the control in total woody fuel loading or any of the fuel categories with the exception of the one‐hour fuels; the treatment unit contained significantly more one‐hour fuels than the control (p=0.02, α= 0.05). Table 1. Estimates of fuel loading for woody fuel classes within masticated treatment units and control. Unit n Treatment Control Fuel loadings (tons per acre) 1 hr 10 hr 100 hr 1000 hr Total Woody 13 0.6 (±0.1) 4.1(±1.1) 5.6 (±2) 1.8(±1) 12.2(±2.6) 5 0.3 (±0.1) 2.9 (± 2) 6.0(±3.8) 1.9(±1.1) 11.1(±6.3) 10.0
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Figure 4. Differences in fuel loadings between mastication unit and the control. The only significant difference was in the one hour fuel category. Error bars represent the Standard Error (SE). Total fuel loading after treatment was estimated at 12.2 (±2.6) tons per acre within the mastication unit. Post‐mastication fuel loading was concentrated in the 10 and 100 hour fuel classes, which made up 34 and 46 percent of the total woody fuel load respectively. The total estimated fuel load is toward the lower range of estimated fuel loadings for masticated sites; for example, in their study of masticated sites in northern California and southwestern Oregon, Kane et al. (2006) obtained total woody fuel loadings that ranged between 6.8 and 28 tons per acre. NEXT STEPS The mastication unit will be treated with prescribed fire in 2012. Plots and transects will be reread to calculate medusahead frequency and percent cover for one to five years following treatment. Analysis will be conducted to determine the response of medusahead to treatments and to evaluate the effect of different fuel loadings on medusahead cover within individual plots. REFERENCES Coppoletta, M. 2006. Testing the effects of flaming as a method of medusahead (Taeniatherum caput‐
medusae) control on the Plumas National Forest. Pages 56‐59 in Proceedings of the California Invasive Plant Council Symposium. Vol. 10. California Invasive Plant Council, Berkeley, CA. Kan, T., and O. Pollak. 2000. Taeniatherum caput‐medusae (L.) Nevski. Pages 309‐312 in R. Randall and M. Hoshovsky, editors. Invasive Plants of California’s Wildlands. University of California Press, Berkeley and Los Angeles, California. Kane, J.M., Knapp, E., Varner, JM. 2006. Variability in loading of mechanically masticated fuel beds in northern California and southwestern Oregon. RMRS‐P‐41, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fort Collins, CO, pp. 341–350 Rice, P. 2005. Fire as a tool for controlling nonnative invasive plants. Center for Invasive Plant Management, Bozeman, MT. Van Wagdendonk JW, Benedict JM, Sydoriak WM. 1996. Physical Properties of Woody Fuel Particles of Sierra Nevada Conifers. International Journal of Wildland Fire 6: 117–123.