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| Titel |
Effectiveness of two contrasting mulching rates to reduce post-fire soil and organic matter losses |
| VerfasserIn |
Flavio Silva, Sergio Prats, Diana Vieira, João Puga, Rita Lopes, Óscar González-Pelayo, Ana Caetano, Isabel Campos, Jacob Keizer |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150654
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| Publikation (Nr.) |
 EGU/EGU2017-15136.pdf |
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| Zusammenfassung |
| Wildfire-affected soils can reveal strong responses in runoff generation and associated soil (fertility) losses, thereby constituting a major threat to the typically shallow and poor forest soils of the Portuguese mountain areas. Mulching with logging residues from these forests has proven to provide a protective soil cover that is highly effective in reducing post-fire runoff and especially erosion (Prats et al., 2012, 2014, 2016a, 2016b). However, these past experiments have all applied comparatively large amounts of forest residues, in the order of 10 Mg ha-1, so that the relationship between application rate and effectiveness is still poorly known. Such relationship would nonetheless be of crucial importance for the employment of forest residue mulching in practice, as one of the possible emergency stabilization measures to be contemplated in post-fire land management of a recently-burned area. Further research gaps that exist in relation to post-fire forest residue mulching include its effectiveness in reducing soil fertility losses (C, N, P; Ferreira et al., 2016a, 2016b) and in minimizing export of contaminants (especially PAHs and metals; Campos et al., 2016), and its (secondary) impacts on soil biological activity and diversity (Puga et al., 2016) and on forest productivity (including through the addition of organic matter to the soil surface, partially replacing the burned litter layer; Prats et al. 2016b).
In the framework of the EU-project RECARE, the effectiveness of two contrasting mulching rates with forest logging residues has been tested following a wildfire that on August 9th – 10th 2015 consumed some 715 ha of eucalypt plantations in the Semide municipality, central Portugal. Commercially-available logging residues (chopped bark and twigs) from eucalypt plantations were purchased, transported to the study site and applied to six out of nine 16 m2 erosion bounded plots that had been installed in a burned eucalypt plantation using a randomized block design with three blocks. Mulching was applied at a “standard” rate of 8.0 Mg ha-1 as had been done in prior field tests (Prats et al. 2012, 2016a, 2016b) as well as at a reduced rate of 2.6 Mg ha-1. This reduced rate was selected based on the results of laboratory experiments that had been carried out using a 1.00 m × 0.75 m free drainage soil flume under artificial rainfall and run-on (Abrantes et al., 2017). These results suggested that this reduced rate was somewhat less effective as the “standard” rate.
The results from the first post-fire year in Semide showed that both the “standard” and the reduced mulching rate were not only highly effective in reducing soil losses (with more than 85 %) but also capable of avoiding erosion rates clearly exceeding the tolerable soil loss threshold of 1 Mg ha-1 y-1 proposed by Verheijen et al. (2009). Soil losses amounted, on average, to 8.0 Mg ha-1 y-1 at the untreated plots as opposed to 1.1 and 0.3 Mg ha-1 y-1 at the plots with low and “standard” mulch application rates, respectively. This difference in effectiveness between the two application rates could be related to their difference in protective mulch cover, which corresponded to 48 and 77 % for the low and the “standard” mulching rate, respectively.
References
Abrantes J.R.C.B., de Lima J.L.M.P., Prats S.A., Keizer J.J., 2017. Assessing soil water repellency spatial variability using a thermographic technique: an exploratory study using a small-scale laboratory soil flume. Geoderma 287, 98-104
Campos I., Abrantes N., Keizer J.J., Vale C., Pereira P., 2016. Major and trace elements in soils and ashes of eucalypt and pine forest plantations in Portugal following a wildfire. Science of the Total Environment 572: 1363–1376
Ferreira R.V., Serpa D., Cerqueira M.A., Keizer J.J., 2016. Short-time phosphorus losses by overland flow in burnt pine and eucalypt plantations in north-central Portugal: A study at micro-plot scale. Science of the Total Environment 551–552: 631–639
Ferreira R.V., Serpa D., Machadoa A.I., Rodríguez-Blanco M.L., Santos L.F., Taboada-Castro M.T., Cerqueira M.A., Keizer J.J., 2016. Short-term nitrogen losses by overland flow in a recently burnt forest area in north-central Portugal: a study at micro-plot scale. Science of the Total Environment 572: 1281–1288.
Prats, S.A., MacDonald, L.H., Monteiro, M., Ferreira, A.J.D., Coelho, C.O.A., Keizer, J.J., 2012. Effectiveness of forest residue mulching in reducing post-fire runoff and erosion in a pine and a eucalypt plantation in north-central Portugal. Geoderma 191: 115-124.
Prats, S.A., Malvar, M.C., Martins, M.A.S., Keizer, J.J., 2014. Post-fire soil erosion risk assessment and mitigation: new approaches for reducing runoff and soil erosion in Portugal. Cuardernos de Investigatión Geográfica 40: 403-427.
Prats SA., Wagenbrenner J., Malvar MC., Martins MAS., Keizer JJ., 2016
Mid-term effectiveness of mulching-based treatments in central Portugal.
Science of the Total Environment 573: 1242–1254
Prats S.A., Wagenbrenner J.W., Martins M.A.S., Malvar M.C., Keizer J.J., 2016
Hydrological implications of post-fire mulching across different spatial scales
Land Degradation and Development 27: 1440-1452
Puga J., Abrantes, N., Oliveira M.J.S., Vieira, D.C.S., Faria., S.R., Gonçalves F., Keizer J.J., 2016. Long-Term Impacts of Post-Fire Mulching on Ground-Dwelling Arthropod Communities in a Eucalypt Plantation. Land Degradation and Development, in press. DOI: 10.1002/ldr.2583
Verheijen, F.G.A., Jones, R.J.A., Rickson, R.J., Smith, C.J., 2009. Tolerable versus actual soil erosion rates in Europe. Earth Science. Reviews. 94: 23-38. |
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