Un incendie modifie la configuration spatiale de la disponibilité des éléments nutritifs dans les sols de forêts de Pinus canariensis

Abstract

Keywords:forest wildfire / ionic exchange membrane / SADIE / soil nutrient availability / spatial heterogeneity Abstract • Soil resources are heterogeneously distributed in terrestrial plant communities. This heterogeneity is important because it determines the availability of local soil resources. A forest fire may change the spatial distribution of soil nutrients, affecting nutrition and survival of colonizing plants. However, specific information on the effects of ecosystem disturbance on the spatial distribution of soil resources is scarce.• We hypothesized that, on a short-term basis, wildfire would change the spatial patterns of soil N and P availability. To test this hypothesis, we selected two Pinus canariensis forests burned in 2005 and 2000, respectively, and a third forest that was unburned since at least 1990 (unburned). We incubated ionic exchange membranes (IEMs) in replicated plots to estimate soil N and P availability and characterized the spatial pattern using SADIE (Spatial Analysis by Distance Indices).• Mineral N, NO 3 -N and PO 4 -P availability, and aggregation and cluster indices for all nutrients were higher in the 2005 wildfire plots than in the 2000 wildfire and unburned plots.• Our results suggest that surviving plants or new individuals becoming established in a burned area would find higher soil resources, but also higher small-scale heterogeneity in nutrients, which may have a major impact on the performance of individual plants and on the forest structure and dynamics.Mots-clés : feu de forêt / membrane d'échange ionique / SADIE / disponibilité des éléments nutritifs du sol / hétérogénéité spatiale Résumé -Un incendie modifie la configuration spatiale de la disponibilité des éléments nutritifs dans les sols de forêts de Pinus canariensis.• Les ressources du sol sont distribuées de manière hétérogène dans les communautés végétales terrestres. Cette hétérogénéité est importante car elle détermine la disponibilité locale des ressources du sol. Un feu de forêt peut changer la répartition spatiale des éléments nutritifs du sol, affectant la nutrition et la survie des plantes colonisatrices. Cependant, des informations précises sur les effets des perturbations des écosystèmes sur la répartition spatiale des ressources du sol sont rares.• Nous avons émis l'hypothèse qu'à court terme, un feu de forêt pourrait modifier les modèles de répartition spatiale de disponibilité de N et P dans le sol. Pour tester cette hypothèse, nous avons sélectionné deux forêts de Pinus canariensis qui ont brûlé respectivement en 2005 et 2000, et une troisième forêt qui n'a brûlé depuis au moins 1990 (non brûlée). Nous avons incubé des membranes échangeuses d'ions (IEMs) dans plusieurs parcelles pour estimer la disponibilité du sol en N et P et nous avons caractérisé le modèle spatial en utilisant SADIE (Analyse spatiale en fonction d'indices de distance).• N-minéral, N-NO 3 , disponibilité en PO 4 -P, agrégation et indices de cluster ont été plus élevés dans les parcelles incendiées en 2005 que dans celles ince...

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