Trends in Recovery of Mediterranean Soil Chemical Properties and Microbial Activities After Infrequent and Frequent Wildfires

Abstract

Since the 1970s, increase in fire frequency has been observed in all European Mediterranean regions. The objectives of this study were (1) to determine the effects of wildfire frequency on the recovery at short‐ and long‐term of soil chemical and microbial properties and (2) to identify the mechanisms underlying the recovery of these sites properties. Soils from 17 plots (Maures mountains range, Var, France) were classified into 5 wildfire regimes (i.e. not burned since at least 57 years ago, infrequently and frequently burned‐with time since fire between 4 and 17 years). Soil samples from these plots were analysed for their nutrient content, chemical functions of soil organic matter (SOM) using FT‐MIR spectroscopy and microbial mineralising activities. Our results showed that the frequent wildfire regime slowed down the recovery in the short term of SOM spectroscopic properties and nutrient availability. Both low quantity and low quality (i.e. high percentage of aromatic and phenolic organic forms) of soil organic matter were found to be related to soil microbial recovery at 4 years after frequent wildfires. The frequent wildfires improved the recovery in net nitrification and nitrate content, leading to an increase in catabolic evenness and a recovery in microbial C‐substrate utilisation profiles between 4 and 17 years. However, frequent wildfires slowed down the recovery of hydrolytic enzyme pool (i.e. FDA hydrolases) and phenol oxidase activity, both involved in soil C cycling. Overall, our observations suggest that 4 fires in 50 years is a threshold beyond which soil quality may be endangered. Copyright © 2011 John Wiley & Sons, Ltd.

Revisión de las investigaciones a nivel molecular sobre el impacto del fuego en la materia orgánica del suelo: progresos en el siglo XXI

“…A modo de resumen, se podría decir que el fuego suele causar a corto plazo una drástica reducción de la biomasa microbiana del suelo (Villar et al, 2004). Por lo general, las bacterias se muestran más resistentes que los hongos a las condiciones post-fuego, produciéndose frecuentemente un incremento en la población bacteriana (Guénon et al, 2013). Igualmente, tras un incendio, suele tener lugar un incremento en la concentración de nutrientes asimilables (mayoritariamente en forma de componentes de la cenizas solubles en agua), que estarán disponibles para los organismos (Bárcenas-Moreno et al, 2011).…”

Influences of Black Locust (Robinia pseudoacacia L.) afforestation on soil microbial biomass and activity

“…Haris (2003) clearly affirmed that the microbial community serves as an indicator of the re-establishment of connections between ecological functions of the biota in disturbed ecosystems. Despite the large variations in mineralogy, soil texture and land use type, extreme environments usually show low organic matter and very low microbial biomass contents, which indicate poor soil quality and limited site productivity (Sparling 1997, Guénon et al 2013.…”

“…Haris (2003) clearly affirmed that the microbial community serves as an indicator of the re-establishment of connections between ecological functions of the biota in disturbed ecosystems. Despite the large variations in mineralogy, soil texture and land use type, extreme environments usually show low organic matter and very low microbial biomass contents, which indicate poor soil quality and limited site productivity (Sparling 1997, Guénon et al 2013.Soil basal respiration is a well-established parameter to be measured through the decomposition process, and it is defined as the overall activity or energy spent by the indigenous microbial pool (Anderson & Domsch 1990, Sparling 1997. Insam et al (1991) argued that soil basal respiration reflects the availability of slow-flowing C for microbial permanence and is a measure of basic turnover rates in soil.…”

Soil microbiological properties and enzymatic activities of long-term post-fire recovery in dry and semiarid Aleppo pine (<i>Pinus halepensis</i> M.) forest stands

“…Some long-term studies appreciated that soil organic matter and microbial communities can recover to the pre-fire levels in the Mediterranean region, taking into account study areas dominated by Quercus ilex L., Quercus suber L. and Pinus pinaster Aiton subsp. pinaster (Guénon et al, 2013). The aim of this study is to investigate soil microbiological and soil enzymatic activities in different semiarid and dry Aleppo pine forest ecosystems affected by the following: (i) a wildfire event occurred 17 years ago; (ii) a wildfire event 17 years ago and treated with early thinning 12 years earlier; (iii) an Aleppo pine in a mature stand not affected by wildfire with no silvicultural treatments.…”