SummarySome aspects of the genesis of terrae rossae are still subject to controversy while others related to the genesis of the mineral fraction have been studied very little. We have studied four terrae rossae over limestone (two Chromic-Leptic Luvisols, a Rhodi-Leptic Luvisol and a Chromi-Leptic Cambisol) in Sierra Ga dor (Almerõ a, southern Spain), in particular the various formation processes by (i) examination of their morphological, analytical and mineralogical characteristics (including crystallochemical parameters of the mica), (ii) examination of the insoluble residue of the gravel and rock, (iii) scanning electron microscopy (SEM) of sand and silt grains, and (iv) examination of the geochemistry of the soil solution. We have investigated the autochthonous or allochthonous nature of the soil material (fine earth and gravel) in relation to the rocky substrate, concluding that both origins are possible. Our SEM study of the morphology of the quartz grains shows that some are insoluble residue and some are probably wind blown from desert and coastal sources. The micas in the fine earth fractions are inherited from the insoluble residue. Comparison of the crystallochemical parameters of micas in the insoluble residue and the soil clay shows that the clay has more Si IV and (Fe, Mg) VI , and less Al IV , Al VI and x (layer charge) than the insoluble residue. It also has fewer polytypes 2M 1 and more 1M and has a smaller crystal size, especially in B horizons. The kaolinite is of varied origins including neoformation and inheritance from underlying rock. Some of the kaolinite and some mica has been blown in from elsewhere, probably from desert and coastal sources. The soils have undergone other typical processes of terrae rossae including dissolution of carbonate, illuviation of clay and iron oxides, and rubifaction.

Smouldering of the forest subsurface can be responsible for a large fraction of the total fuel consumed during wildfires. Subsurface fires can take place in organic material stored in shallow forest layers such as duff or humus, and in deeper layers such as peat, landfills and coal seams. These fires play a major role in the global emission to the atmosphere, the destruction of carbon storage in the soil and the damage to the natural environment. Burning dynamics in two different ecosystems affected by smouldering wildfires are studied here; boreal peat and Mediterranean humus. A series of small-scale smouldering experiments have been conducted under laboratory conditions to study the ignition and the severity to the soil. The experimental set-up allowed the temperature and velocity of the fire front to be measured for different fuel moisture contents. The two fuels, peat and humus, were tested and the results are compared.

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RESUMEN. Relaciones Suelo-Planta en Bosques de Abies pinsapo Boiss. Disponibilidad de Nutrientes y Estatus Nutricional. Se han evaluado las relaciones entre las propiedades del suelo y el estado nutricional de los árboles en pinsapares del Paraje Natural Los Reales de Sierra Bermeja y del Parque Natural Sierra de las Nieves (Málaga-España). Sc seleccionaron pinsapares que difieren en cuanto a su estado sucesional (masas agradativas versus maduras) y sustrato litológico (serpentinas versus calizas), en los que se evaluaron variables morfoedáficas de perfiles de suelo, y se analizaron las concentraciones de nutrientes en muestras de suelo, hojarasca y acículas. Los suelos de pinsapares calcáreos en fase agradativa (Yunquera) mostraron las menores concentraciones de macro y micronutrientes totales. Esto se correspondía con contenidos también mínimos de N y P en tejidos foliares, indicando la existencia de un estrés nutricional general, como es habitual en masas forestales en fase de exclusión de tallos (máxima competencia intraespecífica). No obstante, la presencia de relaciones NIP foliares normales implica que dicho estrés nutricional no ha desencadenado desbalances internos entre dichos nutrientes en los árboles. En pinsapares calcícolas maduros (Ronda), la mayor acumulación de materia orgánica en la hojarasca y el suelo superficial se relaciona con un aumento de la disponibilidad de nutrientes en el suelo, y una reducción en el estrés nutricional de los árboles. El pinsapar serpentinícola de Los Reales de Sierra Bermeja mostró niveles anormalmente elevados de N, y de las relaciones NIP, tanto en el suelo como en los tejidos foliares. Estos síntomas son característicos de ecosistemas forestales en una fase temprana del denominado síndrome de saturación de nitrógeno, asociado a disfunciones en el ciclo del N.Palabras clave. Abies pinsapo, Sierra de las Nieves, Sierra Bermeja, macronutrientes, relaciones suelo- planta.ABSTRACT. Soil-Plant relationships in Abies pinsapo Boiss-Fir Forests. Nutrient Availability and Nutritional Status. Relationships between soil profile properties and the tree nutritional status have been evaluated in Pinsapo-fir (Abies pinsapo, Boiss.) forests at Los Reales de Sierra Bermeja Natural Site and Sierra de las Nieves Natural Park (Málaga -Spain). Pinsapo stands widely differing in sucesional status (agradative versus old-growth stands) and lithology (serpentinic versus calcarcous substrate) were selected. Soil profile-development and nutrients in soil, littler and needles have been compared to the plant community development and parent material. Overall macro- and micronutrients availability was low in young calcareous pinsapo stands (agradative phase). Foliar tissues at these stands showed minima N and P concentrations, indicating a general nutritional stress; although nutritional unbalances were absence as indicated by normal NIP ratios in foliar tissues. As a consequence of the progressive build-up of the organic matter pool in the litter and surface soil layers along with succession, nutrient availability in calcareous pinsapo forests was the highest at the old-growth stands, and the tree nutritional stress appeared to be relieved. The serpentinic pinsapo forest at Los Reales de Sierra Bermeja showed very high levels of nitrogen and N/P ratios, both in the soil and foliar tissues. These preliminary results suggest this pinsapo forest is at an early phase of the N saturation syndrome.Keywords. Abies pinsapo, Sierra de las Nieves, Sierra Bermeja, macronutrients, plant-soil relations.

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