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Research Project Summary: Seasonal fire effects in a Saskatchewan plains rough fescue prairie

• RESEARCH PROJECT SUMMARY CITATION
• STUDY LOCATION
• SITE DESCRIPTION
• PREFIRE PLANT COMMUNITY
• FIRE SEASON/SEVERITY CLASSIFICATION
• PLANT PHENOLOGY
• FIRE DESCRIPTION
• FIRE EFFECTS ON PLANT COMMUNITY
• FIRE MANAGEMENT IMPLICATIONS
• REFERENCES

FRES38 Plains grasslands [3]
SRM613 Fescue grassland [5]

Kernan Prairie's continental climate brings average winter low temperatures of -18 °C, summer highs of 19 °C, and annual precipitation levels of 360 mm, 30% of which is snow [2]. The soils in the study area are fine-textured Chernozems, which are described as dark, organically rich, with calcium carbonate layers below the A horizon [2]. The soils of Kernan Prairie have a surface bulk density of 1.3g/cm³. The plains rough fescue (Festuca hallii) grasslands studied occupied prairie depressions.

Researchers reported that the precipitation levels the year of the fires were 5% above normal for the months of April through September. August rainfall was much greater than normal the year fires burned. From April through September of the 1st postfire year, precipitation levels were 17% above the long-term averages.

Prior to the fires in April 1998, researchers established 4 contiguous 10×10 m plots in an area with uniform plant cover, soil conditions, and topography [1,2].

Prior to igniting the fires, firebreaks were established around the plot to be burned. Fuel load and moisture content were determined from 0.25×0.5 m quadrats before burning. Ring fires were set in the center of the plot. Researchers monitored weather conditions and flame temperatures at 1 cm beneath the soil surface and 5, 10, 20, 50, and 100 cm above the ground [1].

Fuel load and moisture content were greatest for the fall fire and least for plots burned in spring (see table below). Fall and summer fuel loads were very similar, but fuel moistures were much greater in the fall. The fuel loads reported for this study are much greater than the average 450 g/m² fuel load reported by Redmann and others [4], who burned rough fescue-dominated sites within the Kernan Prairie in the late 1980s.The table below gives average fuel loads and fuel moistures (±s) prior to spring, summer, and fall burning [2].

Air temperature and relative humidity were highest during the summer fire. Air temperature and relative humidity were lowest during the spring fire. Wind speed was similar for all fire seasons.

The researchers measured fire temperature regimes using 4 replicate chromelalumel thermocouples at each of the above ground distances shown below. Temperatures were recorded at 10-second intervals. The summer fire produced the highest soil and aboveground temperatures. Fire temperatures remained above 50 °C for 5 minutes or longer at 5, 10, and 20 cm above the soil surface during the summer fire. Litter accumulation and low soil moisture were identified by the researchers as the probable causes of increased soil temperatures during the summer fire. The fall and spring fires produced similar fire temperature regimes. However, the spring fire produced temperatures greater than 50 °C for almost 2 minutes longer than the fall fire at 5 cm above the soil surface. The table below provides the average maximum fire temperatures and durations for the seasonal fires.

Grasses and shrubs were significantly taller (on the unburned plot than on any of the burned plots at the end of the 2nd postfire growing season. However, biomass production of grasses and shrubs was significantly greater (P≤0.05) on the fall burned plot than on the unburned plot. Forb biomass production was greater on all burned plots than on the unburned plot, although not significantly. Forb biomass was greatest on the spring burned plot. The mean biomass (g/m²±s) of grasses at end of the 2nd postfire growing season is given below:

Individual species were also investigated. The following tables and remarks compare burned and unburned plots at the end of the 2nd postfire growing season. Rough fescue coverage was greatest on the spring burned plot. Sun sedge (Carex inops subsp. heliophila) coverage was greater on all burned plots than on the unburned plot. Coverage of most other graminoid species was lower or similar on burned plots than on the unburned plot. Kentucky bluegrass coverage was much lower on spring and summer burned plots than on unburned or fall burned plots. Porcupinegrass (Hesperostipa spartea) coverage was lowest on the fall burned plot and greatest on the unburned plot. The complete list of graminoid species and their percent coverage on burned and unburned plots at the end of the 2nd postfire growing season is given below.

The effect of fire on Kernan Prairie forb species was variable. Few species had greater density on all 3 burned plots; however, most forbs had their greatest density on 1 of the burned plots. The same was true for the 2 shrub species. Forb and shrub densities (stems/m²) on burned and unburned plots at end of 2nd growing season are provided below [1].

REFERENCES:

1. Archibold, O. W.; Ripley, E. A.; Delanoy, L. 2003. Effects of season of burning on the microenvironment of fescue prairie in central Saskatchewan. Canadian Field Naturalist. 117(2): 257-266. [48371]

2. Brady, Nyle C. 1984. The nature and properties of soils. 9th edition. New York: Macmillan Publishing Company. 750 p. [53627]

3. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; Lewis, Mont E.; Smith, Dixie R. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p. [998]

4. Redmann, R. E.; Romo, J. T.; Pylypec, B.; Driver, E. A. 1993. Impacts of burning on primary productivity of Festuca and Stipa-Agropyron grasslands in central Saskatchewan. The American Midland Naturalist. 130(2): 262-273. [35391]

5. Shiflet, Thomas N., ed. 1994. Rangeland cover types of the United States. Denver, CO: Society for Range Management. 152 p. [23362]