Antonio Lobo Gallardo

LEAF DECOMPOSITION IN TWO MEDITERRANEAN ECOSYSTEMS OF SOUTHWEST SPAIN: INFLUENCE OF SUBSTRATE QUALITY'

We studied the influence of litter quality on the decomposition rate of leaves from nine Mediterranean shrubs and trees using litter bag methods for a 2-yr period at two ecosystems in southwest Spain. Linear and nonlinear regressions were calculated be- tween mass loss and the concentrations of the major organic and inorganic constituents of leaves (lignin, cutin, cellulose, tannins, crude fat, soluble carbohydrates, nitrogen, and phosphorus) and between mass loss and leaf toughness in order to determine the best predictor of leaf litter decomposition in these ecosystems. In addition, ratios between some of the litter quality parameters were examined as mass loss predictors. Loss of soluble components from leaves was used to define two phases of decomposition: a leaching phase that lasted 2-4 mo and a postleaching phase. Leaf toughness and the ratio of toughness: phosphorus concentration were the best indicators of mass loss during the leaching phase in both ecosystems, and cutin: nitrogen or cutin: phosphorus ratios were the best predictors of mass loss in the postleaching phase, but only in the drier and more nutrient-poor ecosystem. When the two phases were combined, leaf toughness, toughness: nitrogen, and/or cutin: nitrogen significantly explained the mass loss in both ecosystems.

Factors limiting microbial biomass in the mineral soil and forest floor of a warm-temperate forest

Abstract Soil respiration and microbial biomass-N, in the forest floor, and in the top 10cm of the mineral soil, was measured in a warm-temperate forest soil in North Carolina (U.S.A.). We amended soils with nitrogen, phosphorus and sucrose at five different samplings from May 1991 to July 1992. Average microbial biomass-N was 463 μg g −1 in the litter layer and 52.3 μg g −1 in the mineral soil. N fertilization increased microbial biomass in the forest floor but in the mineral soil microbial biomass only responded to P fertilization. Phosphatase activity g −1 of organic matter was four times higher in the mineral soil than in the forest floor. Soil respiration increased with N, P and sucrose additions. We found seasonal differences in soil respiration and microbial biomass through the year with a winter minimum and a summer maximum. The limitation of microbial biomass by P in the mineral soil is explained by the decrease of P availability due to P Sorption by Al and Fe sesquioxides in the upper mineral soil, and by P uptake by roots from the forest floor. Our results suggested that in this forest microbial biomass would not act as a major N sink with increased N deposition.

Carbon and nitrogen limitations of soil microbial biomass in desert ecosystems

Microbial biomass nitrogen was measured in unamended (dry) and wetted soils in ten shrubland and grassland communities of the Chihuahuan desert, southern New Mexico, by the fumigation-extraction method. Microbial biomass-N in dry soils was undetectable. Average microbial biomass-N in wetted soils among all plant communities was 15.3 μg g-1 soil. Highest values were found in the communities with the lowest topographic positions, and the minimum values were detected in the spaces between shrubs. Microbial biomass was positively and significantly correlated to soil organic carbon and extractable nitrogen (NH4+ + NO3-). In a stepwise multiple regression, organic carbon and extractable nitrogen accounted for 40.9 and 5.6%, respectively, of the variance in microbial biomass-N among all the samples. Among communities, the soil microbial biomass was affected by the ratio of carbon to extractable nitrogen. Our results suggest a succession in the control of microbial biomass from nitrogen to carbon when the ratio of carbon to nitrogen decreases during desertification.

Nitrogen immobilization in leaf litter at two Mediterranean ecosystems of SW Spain

Nitrogen immobilization in relation to the dynamics of lignin and tannins in nine different types of leaf litter was investigated during a 2-yr study at two Mediterranean ecosystems of SW Spain. Net nitrogen immobilization for all the species was higher in a forest than in the more nutrient-poor soil of a shrubland. Absolute amount of lignin increased in both ecosystems in the first 2–4 months whereas tannin rapidly decreased in the same time period. Increases in lignin were significantly correlated to losses of tannins during decomposition. Initial tannin content was the best predictor of the maximum amount of immobilized nitrogen in litter in both ecosystems. Mechanisms that could explain the immobilization of nitrogen in litter are discussed.

Factors determining soil microbial biomass and nutrient immobilization in desert soils

We examined the 10-day response of soil microbial biomass-N to additions of carbon (dextrose) and nitrogen (NH4NO3) to water-amended soils in a factorial experiment in four plant communities of the Chihuahuan desert of New Mexico (U.S.A.). In each site, microbial biomass-N and soil carbohydrates increased and extractable soil N decreased in response to watering alone. Fertilization with N increased microbial biomass-N in grassland soils; whereas, fertilization with C increased microbial biomass-N and decreased extractable N and P in all communities dominated by shrubs, which have invaded large areas of grassland in the Chihuahuan desert during the last 100 years. Our results support the hypothesis that the control of soil microbial biomass shifts from N to C when the ratio of C to N decreases during desertification.

Estimating microbial biomass nitrogen using the fumigation-incubation and fumigation-extraction methods in a warm-temperate forest soil

Microbial biomass-N was measured in the top 60 cm of acid soils on a forested slope using the fumigation-incubation and fumigation-extraction methods. Average microbial biomass-N was 54.4 and 68.5 g N m−2, respectively. Statistical differences between methods and depths were detected, but not between sites along the slope. Estimates of microbial biomass-N measured by the two methods were correlated only in samples taken from 0–20 cm (r = 0.77, P < 0.01). With both methods microbial biomass-N decreased rapidly with depth following a multiplicative model. Organic carbon showed a significant curvilinear relationship with microbial biomass-N measured in the 0–20 cm by the fumigation extraction method (r = 0.81, P < 0.001) and by fumigation-incubation (r = 0.72, P < 0.001). In a multiple linear regression with organic C, the pH of the samples improved the relationship with fumigation extraction values (multiple r = 0.82, P < 0.001) and with fumigation-incubation values (multiple r = 0.79. P < 0.001). but pll only explained 4.9 and 5.2% of the variance. When only the 0.20 cm samples are considered, only organic C explained a significant portion of the variance in the distribution of microbial biomass. The N in microbial biomass accounted for 3.3 and 2.6% of the total N in the soil when using the fumigation extraction and the fumigation incubation techniques, respectively. The results obtained using the easier fumigation extraction procedure seem more reliable and predictable by environmental factors than those obtained by fumigation incubation.

Implicaciones teóricas y metodológicas de la evolución de la investigación en Contabilidad de Gestión

RESUMEN El objetivo de este trabajo es conocer la evolución y el estado actual de la Contabilidad de Gestión, así como plantear las que parecen perfirlarse como tendencias de investigación en esta área. Para ello, entendemos la Contabilidad de Gestión de forma amplia como un sistema de información capaz de suministrar toda la información relevante para la gestión empresarial. En concreto, hemos analizado los enfoques teóricos, los métodos de investigatión y las cuestiones abordadas en Contabilidad de Gestión y, subsidiariamente, en Management y Sistemas de Información, disciplinas con la que existen estrechas relaciones. Para ello hemos revisado revistas especializadas, tanto profesionales como académicas; libros, tanto monografías como recopilaciones; trabajos publicados en actas de congresos y seminarios, así como algunos working papers. Como principales conclusiones, pueden destacarse: a) la gran variedad de enfoques y métodos existente para analizar las distintas cuestiones, todos ellos coexistiendo; b) la tendencia a la multidisciplinariedad; c) la preponderancia de los enfoques de corte positivista; d) el auge de los enfoques teóricos que incluyen cuestiones sociológicas e incluso psicológicas, así como de los métodos de investigación cualitativos, y, por último, e) la permanencia de las cuestiones tradicionales junto con las que han irrumpido como consecuencia de la introducción de las nuevas tecnologías y de la creciente consideración de aspectos como el factor humano y el medioambiente, entre otros.

Wildfire changes the spatial pattern of soil nutrient availability in Pinus canariensis forests

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, NO3-N and PO4-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.Résumé• 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-NO3, disponibilité en PO4-P, agrégation et indices de cluster ont été plus élevés dans les parcelles incendiées en 2005 que dans celles incendiées en 2000 et les parcelles non brûlées.• Nos résultats suggèrent que les plants survivants ou les plants en cours d’installation dans une zone brûlée, auront accès à des ressources plus abondantes, mais seront également confrontés à une hétérogénéité plus importante dans la disponibilité en éléments nutritifs. Cette dernière peut avoir un impact majeur sur la performance individuelle des plants et sur la structure et la dynamique forestières.

La investigación empírica en contabilidad de gestión en España: análisis de las publicaciones españolas

RESUMEN En las últimas dos décadas la investigación empírica en Contabilidad de Gestión ha experimentado un importante crecimiento a nivel internacional. Asimismo, recientemente se ha podido percibir un aumento de este tipo de investigación en nuestro país. Por ello, hemos entendido pertinente desarrollar este trabajo cuyo objetivo genérico es ofrecer una visión panorámica de la investigación empírica en Contabilidad de Gestión publicada en las revistas españolas. Más específicamente, pretendemos: 1) constatar el grado en que se realiza investigación empírica en Contabilidad de Gestión en nuestro país, 2) analizar las cuestiones que se abordan en este tipo de trabajos (qué) y 3) identificar sus principales características, haciendo hincapié en los enfoques teóricos y técnicas de investigación que se utilizan (cómo). Para ello, hemos llevado a cabo una revisión bibliográfica de los trabajos empíricos publicados en Actualidad Financiera, Partida Doble, Revista de Contabilidad, Revista Española de Financiación y Contabilidad y Técnica Contable, durante el período 1988 a 2001. En cada artículo hemos analizado, además de los datos identificativos, el tipo de estudio de que se trata, la unidad de análisis, el enfoque teórico seguido, las técnicas y las fuentes de información empleadas, así como los ámbitos temporal y geográfico a los que se refieren. Entre los principales resultados obtenidos, podemos señalar: a) el escaso número de trabajos empíricos en Contabilidad de Gestión publicados en España; b) su importante aumento en términos relativos desde 1995, en particular en los últimos años del período analizado, desde 1999 a 2001, y c) el predominio de las técnicas de investigación cualitativas y de la empresa como unidad de análisis.

El impacto de las adquisiciones transnacionales sobre los sistemas de control: el caso de TESA

RESUMEN El principal objetivo de este trabajo es mejorar nuestro conocimiento sobre el impacto que el cambio organizativo, provocado por un cambio en la propiedad, tiene sobre el sistema de control de la organización vendida y conocer el papel que la Contabilidad de Gestión juega dentro de estos procesos. Para alcanzarlo, hemos desarrollado un estudio de caso longitudinal en una filial de un grupo químico multinacional que opera en nuestro país desde 1973. Como principales resultados podemos destacar: 1) el importante papel que desempeñan los mecanismos no formalizados y de algunos formalizados y, especialmente, 2) el que juega la Alta Dirección durante el proceso de cambio por el que ha atravesado la organización vendida.