Se estudiaron las propiedades del suelo que más influyen en el crecimiento en volumen y el estado nutricional de árboles en plantaciones de Eucalyptus globulus y Pinus radiata en la parte centro-oriental de Asturias, España. Para cada especie se consideraron 10 clases diamétricas de cinco centímetros de amplitud y se derribaron tres árboles dominantes por clase y taxón de edades comprendidas entre 13 y 52 años. Se evaluaron en acículas recolectadas del tercio superior mediante el método de los niveles críticos. Las deficiencias más importantes fueron en P, K y Mg para P. radiata y en N, P y K para E. globulus. Los suelos se muestrearon a una profundidad de 0-20 cm y presentaron un carácter muy ácido, alto contenido de materia orgánica, relación C/N elevada, bajo contenido en bases y P disponible extraído por el método de Mehlich 3, en los dos taxa. El incremento anual medio en volumen con corteza (IAVC) estuvo asociado significativamente con el contenido de Ca en acículas de P. radiata, pero se obtuvo una correlación negativa para dicho elemento y el contenido de P asimilable en el suelo y positiva con el pH. En E. globulus, el IAVC se correlacionó positivamente con el K cambiable, Mg foliar y el P asimilable en el suelo, con una buena correlación entre estos dos últimos. Los resultados resaltan la importancia del equilibrio nutricional en el desarrollo de ambas especies y revelan las necesidades de una fertilización equilibrada.
The relationships among soil parameters, tree nutrition and site index were examined in Pinus radiata D. Don stands in a climatically homogeneous area of NW Spain. Thirty-eight even-aged stands, ranging from 10 to 54 years, were sampled. In each stand, a representative plot of 0.1 ha was selected and different stand variables and parent material were considered. The soils in the study area are strongly acidic, with high proportions of organic matter, high C/N ratios, and low exchangeable base cation and available P concentration extracted by Mehlich 3 method (PM3). Although foliar N was sufficient in every stand studied, widespread deficiencies of K, P and, to a lesser extent, Mg and Ca were diagnosed. The foliar concentrations of P were positively correlated with PM3 and effective cation exchange capacity. The SI values ranged between 9.5 and 28.8 m and were positively correlated with foliar P and extractable K in soil. In the stands developed on quartzite and sandstone lithologies, the SI was negatively correlated with slope and foliar N respectively. The results suggest the importance of site selection and fertilizer treatment in reforestation programmes.Key words: age-height relationship, needle analysis, Pinus insignis, soil analysis. Resumen Influencia de los factores edáficos en el índice de sitio y estado nutricional de Pinus radiata D. Don en Asturias, noroeste de EspañaSe estudia en 38 parcelas de 0,1 ha cada una las propiedades del suelo que más influyen en el índice de sitio (IS) de plantaciones de Pinus radiata D. Don de 10 a 54 años de edad y en su estado nutricional en Asturias, considerando diferentes variables de masa y distinto material parental. Los suelos estudiados presentaron un carácter fuertemente ácido, alto contenido de materia orgánica, relación C/N elevada, bajo contenido en bases y P disponible extraído por el método de Mehlich 3 (PM3). Las deficiencias más extendidas fueron en K y P, observándose en algunas parcelas deficiencias en Mg y Ca. Sin embargo, las concentraciones en N fueron siempre superiores al nivel crítico. El P foliar se correlacionó positivamente con la capacidad de intercambio catiónico efectiva y con PM3. El IS osciló entre 9,5 y 28,8 m y estuvo positivamente correlacionado con la concentración de P en acículas y con el K intercambiable en el suelo en todas las parcelas y negativamente con la pendiente y el N foliar en las parcelas desarrolladas sobre cuarcitas y areniscas respectivamente. Los resultados revelan la importancia de la elección del sitio y la necesidad de fertilización en los programas de reforestación.Palabras clave: análisis de acículas, análisis de suelo, pino insigne, relación altura-edad.
The edaphic factors have been evaluated in a sloping segment of 2,68 ha of the «Tuña» woodland municipality of Tineo, affected for descending controlled burns of Erica and Ulex with a yield of 1,5 ha h-1. The soil alterations, immediately after the controlled burns and to the 7, 30 and 90 day, took place to 0-2, 2-5 and 5-10 cm of depth, showing the existence of a temporary increment of the soil fertility (increase of C, N, K, Ca, Mg and specially of available P). Immediately after the fire, clay fraction diminished and sand it increased and vice versa to the 7, 30 and 90 days of the controlled burns. The increase of soil fertility after the fire it could be taken advantage for the quick establishment of a vegetal cover due to the regrowth of the burned vegetation.
Aim of study: Germination assays are vital in the management of material preserved in germplasm banks. The rules published by the International Seed Testing Association (ISTA) are generally those followed in such assays. In wild species, seed dormancy and inter-population variability increase the difficulty in estimating seed viability. The aim of the present work was to determine the germination requirements of the seeds from different wild populations of pasture grasses species. Area of study: Northwestern Spain Material and methods: Seeds from eight wild populations of different species of Festuca, all from northwestern Spain, were studied. Germination assays were performed under constant and alternating temperature conditions. Treatments for removing seed dormancy (cold stratification and gibberellic acid application) were also applied. A full parametric time-to event model was used for data analysis. Main results: In general, the optimum environmental temperature for germination was around 15°C for the populations of Festuca group ovina, F. gr. rubra and F. gigantea; temperatures of 20-30ºC had a negative effect. All the examined populations, except that of tall fescue (Lolium arundinaceum), showed non-deep physiological dormancy at suboptimal germination temperatures, but this was breakable by the application of gibberellic acid and by cold stratification. Research highlights: There are clear inter- and intra-specific differences in germination requirements that might be associated with place of origin. The ISTA germination assay recommendations for wild members of fescues may not be the most appropriate.
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