Water repellency of air-dried and sieved samples from limestone soils in central Portugal collected before and after prescribed fire

Abstract

Aims Soil water repellency (SWR) in Mediterranean sub-humid environments is poorly studied in soils derived from basic bedrock. This study addressed this gap by comparing SWR in soil samples collected before/ after a prescribed burning in a Mediterranean shrubland overlaying limestone. Methods Sampling was performed on two adjacent slopes (NE/SW) underneath Quercus coccifera, Pistacia lentiscus, Arbutus unedo shrubs, and on bare inter-patches, at two depths (0-2 and 2-5 cm). Samples were sieved at <0.25, 0.25-1, 1-2 and <2 mm and SWR was assessed through the Water Drop Penetration Time (WDPT) in each fraction. Samples were analysed for pH, AS, CaCO 3 and SOM.Results SWR was present before fire, mainly in the <0.25 and 0.25-1 mm fractions at 0-2 cm, which could be explained by SOM (amount and chemical composition). Persistence varied between the two slopes (NE > SW) and the four patches (Arbutus unedo > Pistacia lentiscus ≈ Quercus coccifera > Bare). The low-severity fire slightly increased SWR but did not affect the above-mentioned prefire differences. Conclusions The wax and resins from different shrub species have implications for SWR persistence on the finer soil fractions. Prescribed fire increased the severity of SWR at surface but also its frequency at the subsurface layer.

Contrasting effects of fire frequency on plant traits of three dominant perennial herbs from Chaco Serrano

“…At the interspecific level, as a consequence of sharing ecological and life-history traits, the overall response of the three species was similar. High fire recurrence enhances soil hydrophobicity affecting water infiltration into soil and increasing runoff events (Certini 2005;González-Pelayo et al 2015), which leads to soil erosion and overall lower soil moisture (Shakesby & Doerr 2006). Moreover, coarsetextured soils, as found at our study sites, typically have low available water content; thus, small variations may significantly affect plant growth (Albanesi & Anriquez 2003;Thompson & Troeh 1988).…”

“…This is produced by the recurrent ash deposition that clogs soil pores, creating discreet and continuous water-repellent layers, which reduce hydraulic conductivity and water infiltration (Certini 2005). Simultaneously, the elimination of vegetation and litter layer increases the impact of raindrops and water runoff events, intensifying soil erosion (Certini 2005;González-Pelayo et al 2015). In terms of chemical properties, fire induces organic matter mineralization; thus, organic carbon (C) and nitrogen (N) are partly volatilized and lost to the atmosphere, while phosphorus (P) can be either recycled by plants or lost by lixiviation.…”

Soil Heating at High Temperatures and Different Water Content: Effects on the Soil Microorganisms

“…In this sense, decreases in the heat transfer when the soil water content is higher than 20% has been described [56]. Similarly, low intensity prescribed fires performed on shrublands with a 24% of soil water content did not cause detectable effects on the soil chemical properties [57]; and soils at water holding capacity have been proved to delay the soil heating and cooling faster, compared to dry soils, under experimental heating [55]. This slowdown of the heat transfer related to soil moisture has been recently included in 3D models as well [58].…”

Implicaciones hidrodinámicas de una quema prescrita de baja intensidad en condiciones forestales mediterráneas

“…Es un elemento, que bien de manera natural o bien utilizado por el hombre, ha modelado la mayoría de las áreas forestales del planeta (Neary at al., 2005;Martínez-Murillo et al, 2016). Como elemento natural, ha contribuido a la selección de especies, a la composición de las formaciones vegetales y a su estabilidad (González-Pelayo et al, 2015 ;Fonseca et al, 2017). Sin embargo, los efectos destructores o renovadores del fuego son variados y dependientes de algunos factores como son: (i) aquellos inherentes al incendio (frecuencia, intensidad, severidad, tamaño, forma del incendio y época) y; (ii) aquellos relativos a las condiciones físicas y de vegetación del área afectada (clima, geomorfología, topografía, suelo, composición florística y fenología) (Certini, 2005;Alcañiz et al, 2016).…”