Aboveground soil C inputs in the ecotone between Scots pine

Abstract

Aboveground litterfall from Pyrenean oak (Quercus pyrenaica Willd. a semi-deciduous species), mixed Pyrenean oak-pine and pine (Pinus sylvestris L.) forest stands was surveyed in two sites in a Mediterranean mountain area during a period of 36 and 29 months, respectively. Separation in different litterfall fractions was performed, and C content of each fraction was measured to calculate the C flux to the soil due to litterfall. Our results showed that litterfall input was higher in pine stands than in Pyrenean oak stands (1.8-2.4 Mg C ha -1 year -1 at pine plots and 0.9-1.4 Mg C ha -1 year -1 at oak plots) and mixed plots showed intermediate values. Needles or leaves contributed about 50% to total litterfall, underpinning the importance of the rest of materials in the soil C input. The seasonal pattern showed a maximum in Pyrenean oak stands in autumn-early winter, while the pine stands had the maximum in summer, which is in consonance with the physiology of fall of broadleaves and coniferous trees in these latitudes , but clearly differs from needle-shed in Central and Northern Europe. A dry-spring year corresponded to a lower leaf fall during the following autumn, and leaf abscission came some weeks earlier than a year with a rainy spring.Key words: litterfall; Pinus sylvestris; Quercus pyrenaica; ecotone; Mediterranean mountain. ResumenCaída de hojarasca en un ecotono Pinus sylvestris L.-Quercus pyrenaica Willd. en la Sierra de Guadarrama La tasa de caída de hojarasca en parcelas puras de rebollo (Quercus pyrenaica Willd.), parcelas mixtas de rebollo y pino silvestre y parcelas puras de pino (Pinus sylvestris L.) fue estudiada en dos localizaciones de montaña mediterránea durante 36 y 29 meses, respectivamente. Se llevó a cabo una separación de los componentes de la hojarasca, y se determinó el porcentaje de C en cada una de las fracciones, para calcular un flujo de entrada de C al suelo debido al desfronde. Nuestros resultados muestras que la tasa de caída de hojarasca fue más alta en parcelas de pino que de rebollo, alrededor del doble (1.8-2.4 Mg C ha -1 año -1 en pino frente a 0.9-1.4 Mg C ha -1 año -1 en rebollo); las parcelas mixtas mostraron valores intermedios. Las acículas u hojas contribuyeron alrededor del 50% al total de caída de hojarasca. El patrón estacional mostró un máximo de caída de hojarasca de rebollo en otoño y comienzos de invierno, mientras que en las parcelas de pino, dicho máximo se produjo en verano, lo que es congruente con la fisiología de la caída de hojas o acículas en frondosas y coníferas en estas latitudes, pero desmarcándose de los valores obtenidos en Europa Central y del Norte. Un año con primavera seca coincidió con un desfronde de hojas de rebollo menor; asimismo, la caída de la hoja se adelantó algunas semanas con respecto al año con una primavera lluviosa.

Disentangling the effects of tree species and microclimate on heterotrophic and autotrophic soil respiration in a Mediterranean ecotone forest

“…Confirming our hypothesis, annual R H was highest in the pine stand, where litterfall rates (Diaz-Pines et al, 2011a) and C stored in the topsoil (Diaz-Pines et al, 2011b) are significantly higher than in the oak stand. However, the C turnover rate in soils under pines was roughly twice that of oaks, reflecting the functional traits of leaves and needles Table 5 Seasonal and annual total soil respiration (R s ) and its components (R A : autotrophic, R H : heterotrophic) estimated for each tree species (mean ± SD, n = 3) and given as g C0 2 -C m~ 2 .…”

“…transpiration (Poyatos et al, 2005), low growth rates (Camarero et al, 2010;Sabate et al, 2002;Vayreda et al, 2012) and needle fall period from May to September (Diaz-Pines et al, 2011a). The abundant precipitation in the first half of the year may delay the time at which drought stress becomes critical in the pine growing season.…”

Quantity and quality of litterfall in young oak stands

“…Martin et al (1996) found that the inter-annual variability of litterfall amount in Q. rotundifolia stand was caused by water stress in summer. Dry spring weather was the reason for the lower amount of litterfall also in Q. pyrenaica stand in Spain (Diaz-Pines et al 2011). Finally, precipitation and water availability as a probable cause of differences in litter production were mentioned by Andivia et al (2013) in stands of Q. ilex.…”

Regional-scale stand density management diagrams for Pyrenean oak (Quercus pyrenaica Willd.) stands in north-west Spain

“…As a result of this interest, a wide range of studies have been published in the last few decades. These studies have included the following aspects (amongst others): development of site index curves, in León (Torre 1994), La Rioja (Bengoa 2000), Castilla y León (Adame et al 2006) and Galicia (Díaz-Maroto et al 2010); fitting height-diameter models (Adame et al 2008); modeling mortality (Adame et al 2010); stand yield in terms of biomass (Allué & San Miguel 1991, Carvalho 2005; and estimation of carbon stocks in Pyrenean oak stands, both in soils (Díaz-Pines et al 2011) and in wood (Castaño-Santamaría & Bravo 2012). However, only one stand-level model has been developed to date and this refers to the province of Leon (Bravo et al 2011).…”