Balfour, Victoria

Bodí, Merche B.

Cawson, Jane

Noske, Philip

Sheridan, Gary

Repositori d'Objectes Digitals per a l'Ensenyament la Recerca i la Cultura

Wood and charcoal anatomy. Problems and solutions  Types of ash resultant from burning different vegetation and from varied combustion processes    Merche B. Bodí1,4,5, Gary Sheridan2, Philip Noske2, Jane Cawson2, Victoria Balfour3, Stefan H. Doerr4, Jorge Mataix-Solera5 and Artemi Cerdà1   1 Departamento de Geografia, Universitat de València, Blasco Ibañez 28, 46010, Valencia, Spain; merche.bodi@uv.es, artemio.cerda@uv.es 2 Department of Forest and Ecosystem Science, Melbourne School of Land and Environment, The University of Melbourne, 221 Bouverie St., Parkville, Victoria 3010, Australia; sheridan@unimelb.edu.au 3 College of Forestry, University of Montana, Missoula, MT, 59812, USA; victoria.balfour@umconnect.umt.edu  4 Geography Department, Swansea University, Singleton Park, Swansea SA 8PP, UK; s.doerr@Swansea.ac.uk 5 Departamento de Agroquímica y Medio Ambiente, Universidad Miguel Hernández, Edificio Alcudia, Avda de la Universidad s/n. 03202 Elche, Spain; jorge.mataix@umh.es   Summary: Some of the physical and chemical properties of ash produced from Pinus halepensis collected after a wildfire and Eucalyptus radiata burned by a prescribed fire and under laboratory controlled conditions were determined and compared. The ash was found to be different, depending on the combustion characteristics and vegetation type. The different properties of ash will affect the recovery of the ecosystem after fire.   Key words: ash, ash properties, fire type, temperature of combustion   INTRODUCTION  The intensity of a forest fire and the resulting burn severity can be complex and varied. This variability is a function of fuel load, weather, vegetation type, vegetation and soil moisture, slope, fire climate, topography, time since last burned and area burned (Neary et al., 1999).   Products of forest fire such as soot, charcoal and ash reflect the characteristics of a fire. Ash, in the broad sense is a solid residue of various sizes that can include both organic and inorganic material. As combustion ceases it is deposited and blankets the soil (Scott, 2010; Moody et al., 2009). Depending on the characteristics of the forest fire, ash may have a different colour, organic carbon content, particle size or chemical composition. Therefore ash is an indicator of fire characteristics.  The objective of this work is to compare some physical and chemical properties of different types of ash produced from burning different vegetation and from varied combustion processes.   METHODOLOGY  Four different types of ash were used for the experiment: (i) ash collected after a prescribed fire in a dry Eucalypt forest in Australia, (ii) ash produced by a controlled fire that simulated a low intensity bushfire in dry Eucalypt forest (iii) ash produced by a controlled fire that simulated a high intensity bushfire in dry Eucalypt forest, (iv) ash collected after a low intensity fire in a Spanish Mediterranean forest of Pinus halepensis.  In the simulated low intensity fire, mostly fine leaves and branches were used, the leaves had moisture content of 14.5 %. The fire was circular and was ignited from one edge and allowed to spread by wind until all the fuel was burned (Fig. 1a). Three thermocouples connected to a data logger were used to measure the temperature (average = 300 ºC, maximum = 600 ºC). Leaves (3 % moisture content), branches and logs were used to simulate the high intensity fire. The fire was ignited in a barrel (Fig. 1b) and was allowed to burn for a longer period of time than in the previous fire, again temperatures were measured using thermocouples (average temperature = 500 ºC, maximum = 1234 ºC).  The four types of ash were kept in plastic bags and analysed for bulk density, particle density, particle size, water repellency, pH and cation content (Ca2+, Mg2+, Na+, K+).     FIGURE 1. Ash produced under controlled conditions a) low intensity fire b) high intensity fire.  SAGVNTVM EXTRA - 11 53Wood and charcoal anatomy. Problems and solutions  RESULTS AND DISCUSSION  The Eucalyptus radiata ash collected after the prescribed fire and made by simulating a low severity fire had similar appearance and properties (Table 1). Temperatures of the fire during these two treatments are thought to have been similar. At lower burn temperatures organic material is semi-combusted resulting in the presence of large particles of charcoal. The water repellency of this ash was found to be extreme due to the high content of organic particles (Bodí et al., 2011). The ash produced from the more intense controlled fire had a higher particle density, porosity and pH, the particle size of the material was smaller, which is consistent with the findings of Woods and Balfour (2011), and was hydrophilic. At higher temperatures organic material is fully combusted.  Pinus halepensis ash from a low intensity wildfire in the Mediterranean forest is similar to the ash from Eucalyptus radiata collected after a prescribed fire in terms of particle size and particle density, probably due to the similar combustion temperature. However, Pinus halepensis ash had higher porosity and therefore a lower bulk density and did not exhibit water repellency. The cation content and pH was also higher in the Mediterranean ash possibly due to the difference in species and the underlying basic nature of the lithology in the Pinus halepensis burned area (Úbeda et al., 2009).   CONCLUSION  Ash produced during a forest fire is different depending on the burn characteristics and the vegetation. These different properties will influence the water quality, soil hydrology, air quality, nutrient cycling and the recovery of an ecosystem after a fire.   Ash properties can provide evidence of fire intensity and the type of vegetation burned. Therefore the study of ash may be a great help in assessing wildfire severity.   ACKNOWLEDGEMENTS  This work was supported by a research fellowship FPU (AP2007-04602) from the Spanish Ministry of Science and Innovation.   REFERENCES  BODÍ, M.B., MATAIX-SOLERA, J., DOERR, S.H., CERDÀ, A., 2011. The wettability of ash from burned vegetation and its relationship to Mediterranean plant species type, burn severity and total organic carbon content. Geoderma 160, 599-607. MOODY, J.A., KINNER, D.A., ÚBEDA, X., 2009. Linking hydraulic properties of fire-affected soils to infiltration and water repellency. Journal of Hydrology 379, 291-303.  NEARY, D.G., KLOPATEK, C.C., DEBANO, L.F., FFOLLIOTT, P.F., 1999. Fire effects on belowground sustainability: a review and synthesis. Forest Ecology and Management 122, 51-71.  SCOTT, A.C., 2010. Charcoal recognition, taphonomy and uses in palaeoenvironmental analysis. Palaeogeography, Palaeoclimatology, Palaeoecology 291, 11-39.  ÚBEDA, X., PEREIRA, P., OUTEIRO, L., MARTIN, D.A., 2009. Effects of fire temperature on the physical and chemical characteristics of the ash from two plots of cork oak (Quercus suber). Land degradation & development 20, 589-608. WOODS, S., BALFOUR, V., 2011. Characterizing the hydrological properties of wildfire ash. In: Bento Gonçalves, A. and Vieira, A. (Eds), Fire effects on soil properties, proceedings of the 3rd International Meeting of Fire effects on Soil Properties. Universidade do Minho and CEGOT. TABLE 1. Ash properties.  Ash from Australian dry Eucalyptus forest (Eucalyptus radiata)  Ash properties Prescribed fire Produced in the laboratory simulating a low severity fire Produced in the laboratory simulating a high severity fire Ash from low severity fire in a Mediterranean forest of Pinus halepensis Bulk density (g cm-3) 0.52   0.38 0.35 0.29 Particle density (g cm-3) 1.42   1.35 2.04 1.47 Porosity (%) 0.63  0.72 0.82 0.80 Particle size (%, 2-0.05 mm;  0.05-0.002 mm; <0.002 mm) 60, 38, 2   53, 45, 2 32, 64, 4 73, 26.5, 0.50 Particles > 2 mm (%) 48.24  36.34 43.87 13.64 Water repellency (WDPT -seconds) 3600 3600 <5 <5 pH 7.53 8.87 9.24 9.42 Cation content (mg L-1): Ca2+                                        Mg2+                                      Na+                                     K+ 24.67 9.68 6.60 5.81 45.04 14.12 7.5 5.81 24.29 1.97 8.30 20.42 58.4 12.2 28 9.6 SAGVNTVM EXTRA - 11 54

Types of ash resultant from burning different vegetation and from varied combustion processes

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