University of Minnesota
University of Minnesota
College of Biological Sciences

E012 - Effect of Fire Frequency on Prairie Grassland Vegetation



Experiment 012 was established by Johannes Knops in 1983 to study the impact of four differe

Testing Captionnt fire frequencies on vegetation structure infertile grassland. Aboveground biomass (sorted by species or litter) was sampled four times over the course of the ongoing experiment, with the most recent data dating from 2000. In 2000, percent cover was also measured to estimate non-vascular plant change (lichens, mosses, bare soil, etc.) Light penetration was sampled periodically.

The 24 experimental burn plots are located in an abandoned agricultural field (Field

 B.) Starting in 1984, four treatments were implemented in replicate: annual burning, burning every other year, burning every four years or un-burned control. Burns take place in the early spring, March or April, depending on the snow melt.

Key Findings

Experiment 012 adds an important dimension to the study of fire's role in ecology by studying its effect on a secondary prairie with nutrient poor, sandy soils.

Fire's impact on prairie productivity and species composition strongly depends on the ecosystem's productivity. Long-term fire studies conducted in more productive mesic prairies and grasslands such as Konza prairie, have shown that increased fire frequency can increase productivity in frequently burned watersheds (Briggs and Knapp 1995; Towne and Knapp 1996; Knapp et al. 1998) through the removal of accumulated litter, which strongly decreases light availability at the soil level (Knapp and Seastedt 1986; Collins et al. 1998). Experiment 133, which was carried out in a more productive forest-grassland continuum at Cedar Creek, found that 32 years of different fire frequencies showed in a shift from 90% dominance by trees to 80% dominance by grasses with increasing fire frequency, accompanied by large changes in nitrogen cycling and vegetation composition (Reich et al 2001).

Experiment 012 illustrates that without litter accumulation (which could lead to light limitation) and tree invasion, the impacts of 17 years of different fire treatments on vegetation composition are minor (Fig 1; Knops 2006). The most consistent change was a decrease of C3 grass abundance with increasing fire frequency (Fig 2; Knops 2006), which was driven by the loss of Poa pratensis (Fig 1). Poa, an introduced species, was the most abundant C3 grass, contributing 80% of the biomass in the control burned plots. Other C3 grasses showed no significant effect.

Figure 1. Temporal vegetation changes under the four different burn frequencies; 17/17 years, 9/17 years, 5/17 years, and 1/17 years burning treatments. Given are the means §1 SE. Data were analyzed with a repeated measurement ANOVA of year (df3,60), treatment (df3,20), and year by treatment (Y by T, df9,60) interaction. NSP>0.05; *P<0.05; **P<0.01; ***P<0.001. Significant differences among years are indicated by capital letters (P<0.05 of a LSD comparison), if there was no significant LSD difference among any of the year by treatment interactions. Lower case letters denote P<0.05 of each individual measurement. (Knops 2006) 

Corresponding with the decrease of C3 abundance under increasing fire frequency, there was a significant increase in legume and sedge abundance (Fig. 2; Knops 2006), which is consistent with other studies (Leach and Givnish 1996; Towne and Knapp 1996).
Figure 2. Temporal vegetation changes of the percent plant functional abundance of the biomass under the four different burn frequencies; 17/17 years, 9/17 years, 5/17 years, and 1/17 years burning treatments. Given are the means +-1 SE. Data were analyzed with a repeated measurement ANOVA of year (df3,60), treatment (df3,20), and year by treatment (Y by T, df9,60) interaction. NSP>0.05; *P<0.05; **P<0.01; **P<0.001. Lower case letters denote P<0.05 (Knops 2006)



Methods for e012


Datasets for e012: Effect of Fire Frequency on Grassland Vegetation and Soils

Dataset IDTitleRange of Years (# years with data)
lpe012Percent light penetration1987-1990 (3 years)
adxe012Plant aboveground biomass carbon and nitrogen2000-2010 (2 years)
ple012Plant aboveground biomass data1983-2010 (5 years)
pce012Plant species percent cover data2000-2000 (1 year)
adve012Root biomass2000-2010 (2 years)
adwe012Root carbon and nitrogen2000-2010 (2 years)
aeae012Soil Nitrogen Cycling2010-2010 (1 year)
adye012Soil bulk density2000-2010 (2 years)
adze012Soil carbon and nitrogen2000-2010 (2 years)
nohe012Soil nitrate and ammonium1987-1987 (1 year)

Selected Recent Publications

Hautier, Y.; Tilman, D.; Isbell, F.; Seabloom, E. W.; Borer, E. T.; Reich, P. B.; Anthropogenic environmental changes affect ecosystem stability via biodiversity. Science, 2015, 348, 6232, 336-340 DOI:10.1126/science.aaa1788 2015 [Full Text] e001 e002 e003 e012 e098 e120 e141 e245 e247 e248

Li, Wenjin; Knops, Johannes (Jean) M.H.; Zuo, Xiaoan; Laungani, Ramesh; Carbon and Nitrogen Cycling are Resistant to Fire in Nutrient-Poor Grassland; Soil Sci.Soc.Am.J., 78, 3, 825 - 831 2014 [Full Text] e012

Li, Wenjin; Zuo, Xiaoan; Knops, Johannes, M. H.; Different Fire Frequency Impacts Over 27 Years on Vegetation Succession in an Infertile Old-Field Grassland; Rangeland Ecology & Management, 66(3):267-273; 2013; DOI: 2013 [Full Text] e012

Tilman, D.; Reich, P. B.; Isbell, F.; Biodiversity impacts ecosystem productivity as much as resources, disturbance, or herbivory; Proceedings of the National Academy of Sciences; 2012; 109, 26, 10394-10397 2012 [Full Text] e001 e002 e003 e004 e012 e062 e098 e120 e141 e172