Changes in grassland vegetation following fire in northern Idaho
Gucker, Corey. 2011. Research Project Summary: Changes in grassland vegetation following fire in northern Idaho. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/fire-studies/gucker-and-bunting-2011
Sources
Unless otherwise indicated, the information in this Research Project Summary comes from the following papers:
- Gucker, Corey. 2004. Canyon grassland vegetation changes following the Maloney Creek wildfire. Moscow, ID: University of Idaho. 80 p. Thesis [2].
- Gucker, Corey L.; Bunting, Stephen C. 2011. Canyon grassland vegetation changes following fire in northern Idaho. Western North American Naturalist. 71(1): 97-105 [1].
Common names are used throughout this summary. For a complete list of the common and scientific names of species discussed in this summary see table A1.
Location
Research was conducted in the China and Corral Creek watersheds of the Garden Creek Nature Preserve in the Craig Mountain Wildlife Area. The Craig Mountain Wildlife Area is roughly 20 miles (40 km) south of Lewiston, Idaho, in southern Nez Perce and western Lewis counties [1,2].
Site Description
Study plots occurred in early, mid-, and late-seral communities within the bluebunch wheatgrass-Sandberg bluegrass-arrowleaf balsamroot habitat type [7]. Plots occupied southeastern to southwestern aspects with slopes of 16% to 52% at elevations of 2,612 to 3,432 feet (796-1,046 m).
Prefire Plant Community
Within the study area, plots are dominated by bluebunch wheatgrass, Sandberg bluegrass, arrowleaf balsamroot, yellow starthistle, and brome grasses. Increased abundance of nonnative species including yellow starthistle and cheatgrass indicated early-seral conditions. Increased abundance of bluebunch wheatgrass, Sandberg bluegrass, and arrowleaf balsamroot was characteristic of late-seral plots. Typically, late-seral plots occurred on steep slopes where past grazing and farming impacts on the vegetation were less evident.
Study sites are classified in the plant community and probably historically experienced the fire regime described in the LANDFIRE Biophysical Settings section.
Plant Phenology
Most species were dormant at the time of the mid-August fire.
Fire Description
This study was conducted on burned and unburned sites that were studied for 2 years before [6] and 2 and 3 years following the Maloney Creek Wildfire. All prefire data were obtained from Robins [6]. Study objectives were to evaluate the effects of fire on native and nonnative species.
The lighting-ignited Maloney Creek Wildfire burned approximately 74,515 acres (30,155 ha) and a large portion of the Garden Creek Nature Preserve. Only plots in the China Creek Watershed burned. Plots burned in a low-severity backing fire on 20 August 2000. Humidity ranged from 27% to 33%, air temperature averaged 74.5 °F (23.6 °C), and winds were 0 to 10.4 miles (16.7 km)/h with gusts of up to 21.9 miles (35.2 km)/h when plots in the China Creek Watershed burned.
Fire Season/Severity Classification
Summer, low severity
Fire Effects on Plant Community
Species cover was averaged from a total of 14 unburned plots. There were 14 unburned plots: 4 early-seral, 5 midseral, and 5 late-seral. There were 11 burned plots: 2 early-seral, 6 midseral, and 3 late-seral. Seral stage of the communities was determined by species composition and relative abundance of native and nonnative species. Early-seral communities were dominated by yellow starthistle; late-seral communities were dominated by bluebunch wheatgrass. Midseral communities had moderate levels of yellow starthistle and bluebunch wheatgrass.
Native Grasses
Bluebunch wheatgrass decreased briefly following fire. Bluebunch wheatgrass cover was significantly (P=0.035) lower on burned than unburned sites in the 2nd postfire year, but average cover on burned and unburned plots was not significantly different by the 3rd postfire year. In the 3rd postfire year, bluebunch wheatgrass coverage on burned plots exceeded prefire coverage. Sandberg bluegrass coverage was significantly greater on burned than unburned plots in the 2nd (P=0.045) and 3rd postfire years (P=<0.0001).
Nonnative Grasses
Cheatgrass cover was significantly (P=0.002) greater on unburned than burned plots just before the fire (2000), but by the 3rd postfire year these differences were lost (P=0.343) due to large increases in cheatgrass cover on burned plots. Cover of Japanese brome increased on both burned and unburned plots following the fire, but cover was significantly (P=0.017) greater on unburned than burned plots only in the 2nd postfire year. Coverage on burned and unburned plots was not significantly (P>0.05) different in the 3rd postfire year.
Native Perennial Forbs
Individual fire responses were analyzed for arrowleaf balsamroot, silky lupine, and common yarrow. There were no significant differences in arrowleaf balsamroot coverage on burned and unburned plots in any year. However, average coverage did decrease from nearly 13% just before the fire to 6.8% in the 2nd postfire year. Silky lupine cover decreased slightly on unburned plots and increased on burned plots. By the 3rd postfire year, burned plots had significantly (P<0.0001) greater silky lupine coverage than unburned plots. Common yarrow decreased dramatically on burned plots. Common yarrow cover was significantly greater on burned than unburned plots (P=0.002 in 1999, P=0.014 in 2000) prior to burning. Due to decreases on burned plots, differences in common yarrow coverage on burned and unburned plots were lost after the fire.
Nonnative Forbs
Yellow starthistle coverage was not significantly different on burned and unburned plots in any time before or after the fire. However, yellow starthistle coverage generally decreased over time on unburned plots and was relatively unchanged on burned plots.
Life Form Groups
Many species in the study area contributed low overall plot coverage and were analyzed as groups. Nonnative annual forb cover was significantly (P=0.018) lower on burned plots than on unburned plots prior to the fire, but by the 3rd postfire year coverage was significantly (P=0.003) greater on burned plots. Nonnative annual forb cover increased on both burned and unburned plots following the fire. Native annual forbs also increased on both burned and unburned plots after the fire, but native annual forb cover was significantly (P=0.025) greater on burned than unburned plots in the 3rd postfire year. Data were pooled for several perennial forbs, not analyzed individually (see Native perennial forbs). These forbs increased on both burned and unburned plots, and differences in perennial forb cover on burned and unburned plots were not significantly different. Increases were likely due in part to favorable postfire moisture conditions.
| Year | 1999 | 2000 | 2002 | 2003 | |
|---|---|---|---|---|---|
| Time since fire (years) | Prefire | Prefire | 2 | 3 | |
| Native perennial forbs | |||||
| common yarrow | UB* | 2.26a** | 1.35a | 1.77a | 1.19a |
| B | 4.03b | 2.81b | 1.32a | 0.78a | |
| waha milkvetch | UB | 0.03 | 0.24 | 0.31 | 0.03 |
| B | 0.44 | 0.76 | 1.25 | 0 | |
| Cusick's milkvetch | UB | 0.50 | 0.34 | 0.13 | 1.24 |
| B | 1.05 | 0.19 | 0.48 | 2.18 | |
| arrowleaf balsamroot | UB | 8.57a | 6.81a | 6.85a | 6.54a |
| B | 9.57a | 12.95a | 6.82a | 7.40a | |
| fernleaf biscuitroot | UB | 0.14 | 0.14 | 0.54 | 1.35 |
| B | 0.04 | 0.02 | 0.08 | 0.84 | |
| nineleaf biscuitroot | UB | 0.16 | 0.42 | 1.58 | 1.04 |
| B | 0.40 | 0.39 | 2.20 | 4.02 | |
| silky lupine | UB | 2.34a | 2.39a | 2.26a | 1.31a |
| B | 3.89a | 4.45a | 3.37a | 6.93b | |
| Snake River phlox | UB | 0.20a | 0.27a | 0.71a | 0.39a |
| B | 0.24a | 0.17a | 0.41a | 0.09b | |
| narrowleaf scullcap | UB | 0.81 | 1.62 | 2.66 | 1.87 |
| B | 0.19 | 0.33 | 0.47 | 0.36 | |
| shiny chickweed | UB | 0 | 0.07 | 0.25 | 0.76 |
| B | 0 | 0.02 | 0.97 | 2.18 | |
| meadow deathcamas | UB | 0.09 | 0.24 | 0.43 | 2.06 |
| B | 0.07 | 0.22 | 0.31 | 1.76 | |
| Nonnative annual forbs | |||||
| thymeleaf sandwort | UB | 0.32 | 0.53 | 2.01 | 0.79 |
| B | 0.17 | 0.11 | 3.73 | 0.99 | |
| redstem stork's bill | UB | 0 | 0.04 | 0.28 | 1.33 |
| B | 0 | 0.03 | 0.4 | 1.46 | |
| strict forget-me-not | UB | 0 | 0.01 | 0.01 | 0.33 |
| B | 0.02 | 0.05 | 0.17 | 4.08 | |
| Lewiston cornsalad | UB | 0 | 0 | 0.23 | 0.05 |
| B | 0.04 | 0.04 | 0.99 | 0.01 | |
| Nonnative perennial forbs | |||||
| yellow starthistle | UB | 13.91a | 7.11a | 9.52a | 4.43a |
| B | 7.13a | 7.08a | 6.32a | 6.62a | |
| Native perennial grasses | |||||
| Sandberg bluegrass | UB | 0.27a | 0.29a | 0.39a | 0.28a |
| B | 0.17a | 0.15a | 1.67b | 3.28b | |
| bluebunch wheatgrass | UB | 20.10a | 16.38a | 25.28a | 26.34a |
| B | 17.74a | 18.66a | 15.56b | 21.53a | |
| Nonnative perennial grasses | |||||
| bulbous bluegrass | UB | 0 | 0 | 0.08 | 0.07 |
| B | 0.05 | 0.09 | 1.11 | 1.04 | |
| Nonnative annual grasses | |||||
| Japanese brome | UB | 6.99a | 6.93a | 13.02a | 10.25a |
| B | 9.95a | 5.22a | 6.75b | 8.90a | |
| cheatgrass | UB | 1.36a | 1.46a | 5.96a | 6.26a |
| B | 0.76a | 0.22b | 1.74b | 7.73a | |
| rattail sixweeks grass | UB | 0.08 | 0.42 | 1.70 | 0 |
| B | 0 | 0 | 0.05 | 0 | |
| * UB=unburned, B=burned. **Burned and unburned coverage values with different subscripts within the same species or year are significantly (P<0.05) different. | |||||
Diversity and Evenness
Species richness, Pielou's evenness, Simpson's diversity, and Shannon-Weiner's diversity were evaluated for burned and unburned plots. Species richness on burned and unburned plots was not significantly different in any study year before or after the fire. Species composition was relatively unchanged by fire. Pielou's evenness was not different before the fire but was significantly (P=0.001) greater on burned than unburned plots in the 3rd postfire year. Simpson's and Shannon-Weiner's diversity index were both significantly (P<0.03) greater on burned than unburned plots in the 2nd and 3rd postfire years. Increased evenness and relatively unchanged species richness on burned plots suggests that changes in Simpson's and Shannon-Weiner's diversity reflect increased homogeneity for species coverage and not an addition of species on burned plots.
Seral Stage
For those species typically used to determine seral stage within the bluebunch wheatgrass-Sandberg bluegrass-arrowleaf balsamroot habitat type, differences in a given year between burned and unburned sites were evaluated within early, mid-, and late-seral plots. Sample sizes within a given seral stage were small.
Native Species
There were no significant differences in bluebunch wheatgrass cover on burned and unburned plots in any year or seral stage. However, average bluebunch wheatgrass cover nearly doubled on early-seral burned plots. For all seral stages, the cover of Sandberg bluegrass was significantly (P<0.02) greater on burned than unburned plots in the 3rd postfire year. Arrowleaf balsamroot cover was variable, and high variances affected significance results. Average arrowleaf balsamroot cover decreased slightly but not significantly following the fire in all but the late-seral burned plots.
Nonnative Species
Overall, yellow starthistle cover decreased on both burned and unburned plots (table 1), but slight increases occurred on mid- and late-seral burned plots when data were analyzed by seral stage (table 2). Cheatgrass increased on early-, mid-, and late-seral burned and unburned plots. In the late-seral plots, cheatgrass cover on unburned sites was significantly (P<0.01) greater than burned sites until the 3rd postfire year.
| Year | 1999 | 2000 | 2002 | 2003 | |
|---|---|---|---|---|---|
| Time since fire (years) | Prefire | Prefire | 2 | 3 | |
| Bluebunch wheatgrass | |||||
| Early | UB* | 7.95a** | 10.85a | 14.80a | 15.54a |
| B | 7.17a | 7.31a | 10.01a | 17.32a | |
| Mid | UB | 20.20a | 14.39a | 27.13a | 27.95a |
| B | 17.4a | 19.09a | 16.22a | 23.36a | |
| Late | UB | 29.7a | 22.8a | 31.82a | 34.17a |
| B | 25.5a | 25.37a | 17.92a | 20.66a | |
| Sandberg bluegrass | |||||
| Early | UB | 0.24a | 0.07a | 0.22a | 0.02a |
| B | 0a | 0.07a | 1.32a | 3.23b | |
| Mid | UB | 0.16a | 0.32a | 0.37a | 0.50a |
| B | 0.15a | 0.18a | 1.43a | 2.26b | |
| Late | UB | 0.4a | 0.44a | 0.54a | 0.26a |
| B | 0.32a | 0.16a | 2.37a | 5.35b | |
| Arrowleaf balsamroot | |||||
| Early | UB | 6.77a | 3.97a | 2.35a | 3.44a |
| B | 14.9a | 17.55a | 5.65a | 5.14a | |
| Mid | UB | 7.54a | 5.85a | 9.42a | 5.12a |
| B | 10.8a | 14.4a | 8.30a | 8.08a | |
| Late | UB | 11a | 10.03a | 7.88a | 10.44a |
| B | 3.62a | 7.0a | 4.63a | 7.55a | |
| Yellow starthistle | |||||
| Early | UB | 40.6a | 16.72a | 22.68a | 10.22a |
| B | 32.0a | 33.04a | 21.1a | 16.95a | |
| Mid | UB | 6.33a | 6.29a | 7.57a | 4.03a |
| B | 2.42a | 1.94b | 4.46a | 4.91a | |
| Late | UB | 0.13a | 0.23a | 0.93a | 0.19a |
| B | 0.02a | 0.06a | 0.18a | 3.17a | |
| Cheatgrass | |||||
| Early | UB | 0.89a | 0.58a | 8.01a | 10.70a |
| B | 0.09a | 0.04a | 1.48a | 10.59a | |
| Mid | UB | 2.51a | 2.52a | 3.70a | 4.65a |
| B | 1.37a | 0.34a | 2.38a | 9.07a | |
| Late | UB | 0.59a | 1.09a | 6.57a | 4.33a |
| B | 0b | 0.11b | 0.63b | 3.14a | |
| *UB=unburned, B=burned. **Burned and unburned coverage values with different letters within the same species, year, or seral stage are significantly (P<0.05) different. | |||||
The summer fire in the Garden Creek Preserve canyon grasslands increased the cover of most native and nonnative species. In general, species composition and dominance were unchanged. Findings from this study will be useful in anticipating desirable and undesirable changes in native and nonnative species after fire. Based on the findings from this study, fire exclusion from this area for the sake of weed management does not appear warranted.
| Biophysical Setting | Mean Fire Interval (years) | Fire Severity Percent (%) | ||||||
|---|---|---|---|---|---|---|---|---|
| Code | Fire Regime Group | Low | Mixed | Replacement | All | Low | Mixed | Replacement |
| Series 11390 - Northern Rocky Mountain Lower Montane-Foothill-Valley Grassland | ||||||||
| 11390_10_19 | II-C | 17 | 17 | 0 | 0 | 100 | ||
| Summary | ||||||||
| Minimum | 17 | 17 | 0 | 0 | 100 | |||
| Maximum | 17 | 17 | 0 | 0 | 100 | |||
| Mean | 17 | 17 | 0 | 0 | 100 | |||
| Median | 17 | 17 | 0 | 0 | 100 | |||
| Percentage of fires in 3 fire severity classes, derived from LANDFIRE succession modeling. Replacement-severity fires cause >75% kill or top-kill of the upper canopy layer; mixed-severity fires cause 26%-75%; low-severity fires cause <26%. | ||||||||
| LANDFIRE. 2020. Biophysical settings models and descriptions, [Online]. Washington, DC: U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior; U.S. Geological Survey; Arlington, VA: The Nature Conservancy, (Producers). Available: https://www.landfirereview.org/search.php [96496] | ||||||||
| Common name | Scientific name |
|---|---|
| Forbs | |
| common yarrow | Achillea millefolium |
| thymeleaf sandwort | Arenaria serpyllifolia |
| waha milkvetch | Astragalus arthurii |
| Cusick's milkvetch | Astragalus cusickii |
| arrowleaf balsamroot | Balsamorhiza sagittata |
| yellow starthistle | Centaurea solstitialis |
| redstem stork's bill | Erodium cicutarium |
| fernleaf biscuitroot | Lomatium dissectum |
| nineleaf biscuitroot | Lomatium triternatum |
| silky lupine | Lupinus sericeus |
| strict forget-me-not | Myosotis stricta |
| Snake River phlox | Phlox colubrina |
| narrowleaf scullcap | Scutellaria angustifolia |
| shiny chickweed | Stellaria nitens |
| Lewiston cornsalad | Valerianella locusta |
| meadow deathcamas | Zigadenus venenosus |
| Graminoids | |
| Japanese brome | Bromus japonicus |
| cheatgrass | Bromus tectorum |
| bulbous bluegrass | Poa bulbosa |
| Sandberg bluegrass | Poa secunda |
| bluebunch wheatgrass | Pseudoroegneria spicata |
| rattail sixweeks grass | Vulpia myuros |
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2. Gucker, Corey. 2004. Canyon grassland vegetation changes following the Maloney Creek wildfire. Moscow, ID: University of Idaho. 80 p. Thesis. [51512]
3. Hann, Wendel; Havlina, Doug; Shlisky, Ayn; [and others]. 2010. Interagency fire regime condition class (FRCC) guidebook, [Online]. Version 3.0. In: FRAMES (Fire Research and Management Exchange System). National Interagency Fuels, Fire & Vegetation Technology Transfer (NIFTT) (Producer). Available: http://www.fire.org/niftt/released/FRCC_Guidebook_2010_final.pdf. [81749]
4. LANDFIRE Rapid Assessment. 2005. Reference condition modeling manual (Version 2.1), [Online]. In: LANDFIRE. Cooperative Agreement 04-CA-11132543-189. Boulder, CO: The Nature Conservancy; U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior (Producers). 72 p. Available: http://www.landfire.gov/downloadfile.php?file=RA_Modeling_Manual_v2_1.pdf [2007, May 24]. [66741]
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6. Robins, Sandra S. 2001. Effects of perennial plant competition on the invasibility of canyon grassland communities by Centaurea solstitialis. Moscow, ID: University of Idaho. 54 p. Thesis. [66570]
7. Tisdale, E. W. 1986. Canyon grasslands and associated shrublands of west-central Idaho and adjacent areas. Bulletin No. 40. Moscow, ID: University of Idaho, College of Forestry, Wildlife and Range Sciences. 42 p. [Contribution No. 284; Forest, Wildlife and Range Experiment Station]. [2338]