Fire severity and post-fire mulching effects on N transformation rates of temperate soils during the first critical winter–spring period
Number, extent and severity of wildfires are increasing worldwide, with important on- and off-site impacts on the N cycle. To mitigate post-fire erosion, mulching is increasingly being used; as its effects on the N cycle are poorly known, gross N fluxes were modelled with Ntrace to compare with unbu...
| Autores: | , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2022 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/280626 |
| Acceso en línea: | http://hdl.handle.net/10261/280626 |
| Access Level: | acceso abierto |
| Palabra clave: | Autotrophic nitrification Dissimilatory NO3 reduction Emergency stabilisation techniques Heterotrophic nitrification N mineralization N immobilization Wildfire |
| Sumario: | Number, extent and severity of wildfires are increasing worldwide, with important on- and off-site impacts on the N cycle. To mitigate post-fire erosion, mulching is increasingly being used; as its effects on the N cycle are poorly known, gross N fluxes were modelled with Ntrace to compare with unburnt soils (US) the effects of intermediate (BI) and high severity (BH) burning, and post-fire straw mulching (BIM and BHM). Two wildfires, two time points after the fire and 20 soil-treatment combinations were studied. The mineralization of soil organic N to NH4+ (MSON) increased in BI (1.9-6.9x) with respect to US, with no clear trends observed in BH and mulched treatments. In most soils, NH4+ immobilization in labile (INH4lab) and recalcitrant SOM (INH4rec) was more important than abiotic NH4+ fixation (ANH4) and together were larger (3.5-11x) in BI than in US, while contrasting results were found depending on time after fire (BH, BHM, BIM) and wildfire characteristics (BHM, BIM). Autotrophic nitrification (ONH4) was included in the best model for all soils, whereas heterotrophic nitrification (OSON) was undetectable in most BH soils. Total nitrification (ONH4+OSON) decreased with time after fire in BH, increased in US and BI, and was differently affected by mulching depending on fire severity and time from the fire. While NO3- immobilization (INO3) was frequently modelled only for BI soils, the dissimilatory NO3- reduction to NH4+ (DNRA) was retained in the best models for all soils and it was reduced by soil burning, whereas a short-lived increase was induced by mulching. Denitrification (LNO3), modelled for most soils, was negatively affected by burning and positively by mulching. In summary, wildfires tended to increase MSON and INH4lab, to decrease DNRA and LNO3, and had no clear influence on INO3 and nitrification. These effects are usually mitigated by mulching which, however, tended to enhance nitrification. |
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