Measuring changes in forest floor evaporation after prescribed burning in Southern Italy pine plantations

Abstract

Wildfires are a growing concern in the Mediterranean area. Prescribed burning (PB) is often used to reduce fire risk, through fine fuel reduction. However, the monitoring of PB effects on ecosystem processes is mandatory before its spread. This study aims to assess hydrological effects of PB on the topsoil by controlled laboratory experiments. The evaporation flux successive to interception of a simulated rain in the litter and the fermentation layers was determined using both a water balance approach and an experimental 2 H and 18 O isotopes mass balance approach. PB was performed in spring 2014 in three Southern Italy pine plantations, dominated, respectively, by Pinus pinea L. (in Castel Volturno Nature State Reserve), P. halepensis Mill. (in Cilento, Vallo di Diano e Alburni National Park) and P. pinaster Ait. (in Tirone Alto-Vesuvio Nature State Reserve). In each study site, two cores, both including litter and fermentation layers, were sampled, 18 months after PB, in burned and in near unburned (control) areas, respectively, by means of customized collectors allowing to extract "undisturbed" cores. Afterwards, each core was moved into a lysimeter set-up in the laboratory, under controlled conditions (temperature of 22°C, relative humidity of 50%), to carry out duplicate infiltration and evaporation experiments. To simulate rainfall, 1 L of tap water (=32 mm of rain) was sprinkled uniformly on the litter layer in the lysimeter and intercepted water from the litter and fermentation layer was collected for isotope analysis at two different depths for each layer, two times per day until 2 days after the rain simulation. The results of the water balance and isotope mass balance showed a slightly lower evaporation of intercepted water from the forest floor in burned areas, compared to unburned ones, but in most cases not statistically significant. The isotopic profiles of 2 H and 18 O also confirmed independently this finding, since they showed more enrichment in the unburned areas compared to the areas treated with PB. This could be due to thinner litter layers in burned areas of the three plantations, at least up to 18 months after treatment.

Soil Microbial Diversity, Biomass, and Activity in Two Pine Plantations of Southern Italy Treated with Prescribed Burning

“…This resulted in higher temperatures and more prolonged residence times above 100 • C in the litter and F-layer (Table 1). In both plantations the litter layer thickness had not yet recovered to the prefire levels, at least up to 18 months after the treatment [44].…”

Rainfall partitioning varies across a forest age chronosequence in the southernAppalachianMountains

“…Our model is one of only a few methods that can estimate how variations in litter biomass and climate affect litter interception in forests (Guiditta, Coenders-Gerrits, Wenninger, Greco, & Rutigliano, 2018;Van Stan & Gordon, 2018). Our model is one of only a few methods that can estimate how variations in litter biomass and climate affect litter interception in forests (Guiditta, Coenders-Gerrits, Wenninger, Greco, & Rutigliano, 2018;Van Stan & Gordon, 2018).…”

“…Quantifying variations in litter interception losses remains challenging. Our model is one of only a few methods that can estimate how variations in litter biomass and climate affect litter interception in forests (Guiditta, Coenders-Gerrits, Wenninger, Greco, & Rutigliano, 2018;Van Stan & Gordon, 2018). Other methods used to quantify total understory water fluxes (e.g., understory eddy covariance towers, weighing lysimeters) may not discriminate between litter interception losses, soil evaporation, and transpiration from understory vegetation.…”

Importance of rainfall partitioning in a northern mixed forest canopy for soil water isotopic signatures in ecohydrological studies

“…Water partitioning within the canopy can also influence SF and TF isotopic signatures relative to that of P g , which is relevant to isotopic studies of forest floor interception (e.g., Giuditta et al, ), soil water storage, and movement in the unsaturated zone (e.g., Brodersen, Pohl, Lindenlaub, Leibundgut, & Wilpert, ; Sprenger et al, ; Sprenger, Tetzlaff, Buttle, Carey, et al, ; Sprenger, Tetzlaff, Buttle, Laudon, et al, ) as well as assessments of the source of water available for uptake by vegetation via transpiration (e.g., Brooks, Barnard, Coulombe, & McDonnell, ; Tetzlaff et al, ). The potential for changes in the isotopic composition of precipitation reaching the subcanopy environment has long been recognized (Gat & Tzur, ) and has been attributed to three main processes (Allen, Keim, Barnard, McDonnell, & Brooks, ; Brodersen et al, ): evaporation, isotopic exchange with atmospheric water vapour, and the selection process.…”