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Maranon-Jimenez S.,Grupo de Ecologia Terrestre | Maranon-Jimenez S.,Helmholtz Center for Environmental Research | Castro J.,Grupo de Ecologia Terrestre | Castro J.,Centro Andaluz Del Medio Ambiente CEAMA | And 3 more authors.
International Journal of Wildland Fire

Large amounts of logs and coarse woody debris remain in the ecosystem after wildfires. However, the relevance of the nutrient reservoir contained in the remaining post-fire woody debris for the ecosystem nutrient reserves is rarely considered. In this paper, we determine the carbon and nutrient concentrations in the partially charred wood after a wildfire along an altitudinal gradient and assess the relative magnitude of the nutrient reservoir in the wood in relation to those existing in the first 10-cm soil layer. Soils were poorly developed and nutrients limiting for the vegetation requirements. Charred woody material still contained a relatively high concentration of nutrients compared to those reported for unburnt pine wood, and in general, this decreased with altitude. Partially charred wood represented a considerable pool of nutrients, due to both the relatively high concentrations and to the great amount of biomass still present after the fire. Potential contributions of the charred wood were particularly relevant for N and micronutrients Na, Mn, Fe, Zn and Cu, as wood contained 2-9 times more nutrients than the soil. Post-fire woody debris constitutes therefore a valuable natural element as a potential source of nutrients, which would be lost from ecosystems in cases where it is removed. © IAWF 2013. Source

Maranon-Jimenez S.,University of Granada | Maranon-Jimenez S.,Centro Andaluz Del Medio Ambiente CEAMA | Castro J.,University of Granada | Castro J.,Centro Andaluz Del Medio Ambiente CEAMA

Post-fire coarse woody debris can represent a valuable nutrient reservoir for a regenerating ecosystem, helping to prevent soil fertility losses after a wildfire. However, there is scarce information on its effect on soil nutrient cycling and availability. We established three study sites along an altitudinal gradient in a burnt pine forest (SE Spain). At each site we determined: (1) decomposition rates and nutrient dynamics in charred logs left on the ground, 2 and 4 years after the fire, and (2) available nutrients in the soil and in the microbial fraction below charred logs and in bare soil areas. Despite the relatively slow decay rates in this Mediterranean climate (ca. 10 % of dry weight lost after 4 years), N and P were progressively released by logs, accounting for ca. 40 and 65 % of the initial content respectively after 4 years. This implies that the total aboveground biomass of the burnt forest released around 20 kg ha-1 of N and 2 kg ha-1 of P during this period. The presence of post fire coarse woody debris consistently increased soil organic matter by around 18 %, total C and N by 42 and 26 %, respectively, dissolved organic C and N by 47 %, available inorganic P by 68 %, and microbial biomass and nitrogen by some 36 and 48 %, respectively. By contrast, soil bulk density decreased by ca. 18 % under logs compared to bare areas. Thus, the fire-killed wood was useful in the recovery of soil fertility and nutrient availability. Leaving the post-fire woody debris on site can enhance the biogeochemical sustainability, microbiological processes and soil ecological functioning. The detrimental effect of post-fire salvage logging on soil fertility should be therefore considered when making management decisions. © 2012 Springer Science+Business Media B.V. Source

Maranon-Jimenez S.,University of Granada | Maranon-Jimenez S.,Centro Andaluz Del Medio Ambiente CEAMA | Castro J.,University of Granada | Castro J.,Centro Andaluz Del Medio Ambiente CEAMA | And 9 more authors.
Forest Ecology and Management

After a wildfire, the management of burnt wood may determine microclimatic conditions and microbiological activity with the potential to affect soil respiration. To experimentally analyze the effect on soil respiration, we manipulated a recently burned pine forest in a Mediterranean mountain (Sierra Nevada National and Natural Park, SE Spain). Three representative treatments of post-fire burnt wood management were established at two elevations: (1) "salvage logging" (SL), where all trees were cut, trunks removed, and branches chipped; (2) "non-intervention" (NI), leaving all burnt trees standing; and (3) "cut plus lopping" (CL), a treatment where burnt trees were felled, with the main branches lopped off, but left in situ partially covering the ground surface. Seasonal measurements were carried out over the course of two years. In addition, we performed continuous diurnal campaigns and an irrigation experiment to ascertain the roles of soil temperature and moisture in determining CO2 fluxes across treatments. Soil CO2 fluxes were highest in CL (average of 3.34±0.19μmolm-2s-1) and the lowest in SL (2.21±0.11μmolm-2s-1). Across seasons, basal values were registered during summer (average of 1.46±0.04μmolm-2s-1), but increased during the humid seasons (up to 10.07±1.08μmolm-2s-1 in spring in CL). Seasonal and treatment patterns were consistent at the two elevations (1477 and 2317m a.s.l.), although respiration was half as high at the higher altitude.Respiration was mainly controlled by soil moisture. Watering during the summer drought boosted CO2 effluxes (up to 37±6μmolm-2s-1 just after water addition), which then decreased to basal values as the soil dried. About 64% of CO2 emissions during the first 24h could be attributed to the degasification of soil pores, with the rest likely related to biological processes. The patterns of CO2 effluxes under experimental watering were similar to the seasonal tendencies, with the highest pulse in CL. Temperature, however, had a weak effect on soil respiration, with Q10 values of ca. 1 across seasons and soil moisture conditions. These results represent a first step towards illustrating the effects of post-fire burnt wood management on soil respiration, and eventually carbon sequestration. © 2011 Elsevier B.V. Source

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