-1 Soil phosphorus availability and transformation rates in relictic pinsapo fir forests from southern Spain BENJAMI ´ N VIN ˜ EGLA*, ROBERTO GARCI ´ A-RUIZ, JOSE ´ LIE ´ TOR, VICTORIA OCHOA and JOSE ´ ANTONIO CARREIRA A ´ rea de Ecologı´a, Universidad de Jae´n, Paraje Las Lagunillas s/n, Edif. B3, E-23071 Jae ´n, Spain; *Author for correspondence (e-mail: bvinegla@ujaen.es; phone: +34-(9)53-212791; fax: +34- (9)53-211873) Received 30 March 2005; accepted in revised form 3 October 2005 Key words: Abies pinsapo, Gross mineralization, Net immobilization, Net solubilization, Phosphatase activity, Phosphorus fractionation Abstract. Abies pinsapo fir forests are remnant of temperate-like coniferous forests currently sub- jected to the typical seasonal constraints of Mediterranean-type climates. We have examined for the first time, P availability and cycling in A. pinsapo forests from southern Spain by using both, measurements of concentrations of soil P fractions (resin extractable P, bicarbonate extractable P and NaOH extractable P) and rates of P supply to (P solubilization, P mineralization and phosphomonoesterases (PMEase activity) and P immobilization from the soil solution. Soils from A. pinsapo stands differing in lithology (serpentinitic and calcareous substrates) and successional status (from young-agradative to old-growth stages) were chosen for this study. Labile organic P fractions, PMEase activity and rates of P gross mineralization and immobilization were signifi- cantly higher in agradative stands on serpentines than in successionally comparable calcareous stands. This suggests an important role of the organic P subcycle in the A. pinsapo stand on serpentine. On calcareous lithology, PMEase activity and all soil P transformation rates signifi- cantly increased throughout the successional series. Similarly, all organic and inorganic P fractions measured in old-growth forests showed the maximum values of the series. These trends fit the predictions of standard patterns of P cycling changes along with succession, in which P supply to plants greatly depends on solubilization from mineral forms at early-to-mid successional stages, whereas the importance of processes related to the organic P subcycle increases as succession progresses. Introduction Abies pinsapo Boiss. is an endemic and relictic species, now restricted to small patches in north-facing slopes of coastal mountain-ranges in southern Spain. These stands are remnants of temperate-like Abies forests that covered a much broader area during the last ice-age periods (Carrio´n et al. 2001). Previous studies have demonstrated that the relictic A. pinsapo forests, despite they are currently subjected to mediterranen-type climate, still maintain some canopy- structural and stand-productivity patterns resembling those in typical tem- perate coniferous forests (Arista 1995; Lie´tor 2002). The enormous scientific significance of Abies pinsapo fir-forests relies on the fact that they can be used Biogeochemistry (2006) 78: 151–172 Ó Springer 2006 DOI 10.1007/s10533-005-3698-1