Effect of pasture buffer length and pasture type on runoff water quality following prescribed burning in the Wivenhoe Catchment

Burning of pastures is a management practice adopted by graziers worldwide. When rain falls on burnt pastures, it can lead to increased pollutant transport in runoff. However, this transport can be modified by vegetative buffers which intercept the runoff downslope of burnt areas. This study examines the effects of different pasture buffer lengths (0, 2, and 5 m) on sediment and chemical transport from two pasture sites near Wivenhoe Dam, the main water reservoir for Brisbane City. Simulated rainfall (100 mm/h) was applied to 18 plots on pasture sites after they were burnt, and insoluble and soluble components were measured in the runoff. Most eroded sediment/organic debris accumulated against the first row of the grass buffer strips or was deposited in the upslope backwater region. Buffer length had little impact on the runoff concentrations of NO3– and NO2– (NOx), total Kjeldahl nitrogen, and total nitrogen from the 5-m-length upslope plots but was significant for sediment loss rate, filterable reactive phosphate, ammonium, and total and dissolved organic carbon. Pasture type was significant for NOx, ammonium, sediment loss rate, and total organic carbon only. Burning increased enrichment ratios of nutrients and carbon in the runoff compared with unburnt plots, but a 2-m buffer strip subsequently reduced the enrichment ratio values by >30%. Buffers strips of unburnt pasture grass may provide an effective tool for post-fire erosion control following prescribed burning; however, further work including scaling to larger plot sizes and catchment level is required.

[1]  J. Parlange,et al.  UNSTEADY SOIL EROSION MODEL, ANALYTICAL SOLUTIONS AND COMPARISON WITH EXPERIMENTAL RESULTS , 1996 .

[2]  T. Svejcar.  Animal performance and diet quality as influenced by burning on tallgrass prairie. , 1989 .

[3]  Bofu Yu,et al.  Sediment deposition from flow at low gradients into a buffer strip—a critical test of re-entrainment theory , 2003 .

[4]  W. W. Miller,et al.  Nutrients flow from runoff at burned forest site in Lake Tahoe Basin , 2006 .

[5]  Gary J. Sheridan,et al.  Changes in sediment loads and discharge from small mountain catchments following wildfire in south eastern Australia , 2006 .

[6]  Bahram Gharabaghi,et al.  Development of a Management Tool for Vegetative Filter Strips , 2002 .

[7]  Hossein Ghadiri,et al.  Sediment retention by a stiff grass hedge under subcritical flow conditions , 2007 .

[8]  M. Johansen,et al.  Post‐fire runoff and erosion from rainfall simulation: contrasting forests with shrublands and grasslands , 2001 .

[9]  J. Keizer,et al.  Overland flow generation processes, erosion yields and solute loss following different intensity fires , 2004, Quarterly Journal of Engineering Geology and Hydrogeology.

[10]  T. J. Marshall.  Soil Physics: Third Edition , 1996 .

[11]  G. R. Foster,et al.  Depositional Patterns of Sediment Trapped by Grass Hedges , 1995 .

[12]  I. Prosser,et al.  The effect of wildfire on runoff and erosion in native Eucalyptus forest , 1998 .

[13]  Rory P. D. Walsh,et al.  Nutrient losses in eroded sediment after fire in eucalyptus and pine forests in the wet Mediterranean environment of northern Portugal , 1999 .

[14]  Hossein Ghadiri,et al.  The influence of grass and porous barrier strips on runoff hydrology and sediment transport. , 2001 .

[15]  J. Parlange,et al.  Overland flow to and through a segment of uniform resistance , 2002 .

[16]  Hossein Ghadiri,et al.  Dynamic erosion of soil in steady sheet flow , 2007 .

[17]  B. Bridge,et al.  A multi-purpose rainfall simulator for field infiltration and erosion studies , 2001 .

[18]  Yiqi Luo,et al.  FIRE EFFECTS ON NITROGEN POOLS AND DYNAMICS IN TERRESTRIAL ECOSYSTEMS: A META-ANALYSIS , 2001 .

[19]  P. Robichaud,et al.  A comparison of surface runoff and sediment yields from low- and high-severity site preparation burns , 1994 .

[20]  L. D. Meyer,et al.  Sediment-trapping effectiveness of stiff-grass hedges , 1995 .

[21]  Calvin Wyatt Rose,et al.  Sorbed chemical transport in overland flow. I, A nutrient and pesticide enrichment mechanism , 1991 .

[22]  Michael Warne,et al.  Australian and New Zealand Guidelines for Fresh and Marine Water Quality , 2001 .

[23]  V. Vallejo,et al.  Thermal shock and rain effects on soil surface characteristics: A laboratory approach , 2008 .

[24]  D. M. Orr,et al.  Using fire to manage species composition in Heteropogon contortus (black speargrass) pastures. 1. Burning regimes , 1997 .

[25]  J. Burke,et al.  Runoff and phosphorus export patterns in large forested watersheds on the western Canadian Boreal Plain before and for 4 years after wildfire , 2005 .

[26]  D. Neary,et al.  Fire's effects on ecosystems , 1998 .

[27]  Allen L. Thompson,et al.  Grass Barrier and Vegetative Filter Strip Effectiveness in Reducing Runoff, Sediment, Nitrogen, and Phosphorus Loss , 2004 .

[28]  H. Neue,et al.  Seasonal variation of gross nitrification rates at three differently treated long-term fertilisations sites , 2009 .

[29]  D. M. Orr,et al.  Using fire to manage species composition in Heteropogon contortus (black speargrass) pastures. 2. Enhancing the effects of fire with grazing management , 1997 .

[30]  Coen J. Ritsema,et al.  Soil and water degradation processes in burned areas: Lessons learned from a nested approach , 2008 .

[31]  C. Rose,et al.  Sorbed Chemical Transport in Overland Flow: II. Enrichment Ratio Variation with Erosion Processes , 1991 .

[32]  W. McGill,et al.  Nitrification in three Alberta soils: Effect of temperature, moisture and substrate concentration , 1982 .

[33]  F. Niell,et al.  Soil nitrogen availability and nitrification in Mediterranean shrublands of varying fire history and successional stage , 1994 .