Jason Philip Kaye, Joan Romanyà, V. Ramón Vallejo. The aboveground biomass of all shrubs, one tussock grass, and all trees were estimated

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1 Electronic Supplementary Material PLANT AND SOIL CARBON ACCUMULATION FOLLOWING FIRE IN MEDITERRANEAN WOODLANDS IN SPAIN Jason Philip Kaye, Joan Romanyà, V. Ramón Vallejo I. Allometric equations The aboveground biomass of all shrubs, one tussock grass, and all trees were estimated using allometric equations (Table S1). For all shrubs the equations relate basal diameter to biomass. For the tussock grass Ampelodesmos mauritanica, basal diameter was estimated from the average of the length of the longest side of the tussock and the length perpendicular to the longest side. For trees, allometric equations were based on the diameter at breast height (DBH = diameter at 1.37 m) or DBH and tree height. We did not attempt to accurately measure the height of trees > 4m tall. This had no effect on our estimate of P. halepensis biomass because our allometric equation relating DBH to biomass covered the range of tree diameters observed in our study site (Table S1). However, for Q. ilex, available equations relating DBH to biomass were only available for trees with DBH > 5 cm and height > 4 m (Canadell et al. 1987). For smaller trees, we used a second allometric equation (Floret et al. 1988) relating both DBH and height to biomass (Table S1). We lacked allometric equations for several plants that were rare at our sites. We used the Q. coccifera L. equation for Phillyrea media L., Phillyrea angustifolia L., Quercus ilex L. seedlings, Genista scorpius L., Bupleurum frutiscescens L, Rhamnus alaternus L., Rhamnus lycioides L., Olea europea var europaea L., Clematis vitalba L., Viburnum tinus L., Sorbus domestica L, Ruscus aculeatus L., Arbutus unedo L., Ligustrum vulgare L., and Olea europaea var sylvestris Mill., and Cistus albidus L. allometric equations for Daphne gnidium L., Smilax

2 aspera L., Cistus monspeliensis L., and Cistus salvifolius L. These rare plants accounted for an average of 3 % of the aboveground plant C per transect. Table S1. Allometric equations relating dry aboveground biomass (in g) to diameter (D in cm) and height (H in cm) for trees, shrubs, and a tussock grass found in the study area. Ancillary information includes the Pearson correlation coefficient for the equation (r 2 ), the diameter range (in cm), the number of plants used to develop the equation, and the source of the equation. Species Biomass Equation r 2 Diameter Range Number of Plants Source D = basal diameter of individual stems Quercus coccifera D Baeza, M. J. (pers. comm.) Pistacia lentiscus 59.13D Abril et al Rosmarinus officinalis D Baeza, M. J. (pers. comm.) Erica multiflora D Baeza, M. J. (pers. comm.) Cistus albidus D Baeza, M. J. (pers. comm.) Juniperus oxycedrus D Baeza, M. J. (pers. comm.) Pinus halepensis Seedlings D This study Ulex parviflorus D Baeza, et al D = Stem diameter at breast height Pinus halepensis Trees D e Quercus ilex trees large Quercus ilex trees small 1000*10 [ log(D)] D 2 H NA* < Lledó 1982 Canadell et al Floret et al D = basal diameter of tussock Ampelodesmos mauritanica 9.546D This study *Not available: this information was not provided in the original manuscript.

3 II. Soil organic carbon concentrations Trends in mineral soil C concentration (Fig. S1) were qualitatively similar to patterns described for mineral soil C pool size (Fig. 3). Both the chronosequence and repeatedly sampled sites showed that C concentrations at the 0 to 5 cm depth were higher than controls immediately following fire, but then most sites showed declines within the first 10 years, followed by no change, or a slight increase in C concentration (Fig. S1). There were no differences between burned and adjacent unburned sites for any individual site (Fig S1) or when comparing all burned-unburned pairs sampled in 2003 (n = 4 pairs; df = 3; t = 0.7; P = 0.95). Sites sampled in both 1989 and 2003 showed either no change (from 2 to 16 years for site 3 and 5 to 19 years for site 4) over that time period, or a significant (P < 0.10) increase (from 7 to 21 years for site 6 and from 17 to 31 years for site 9). There were no detectable trends over time or differences between burned and unburned sites for the 5 to 10 cm depth.

4 Mineral soil 0 to 5 cm (%C) Mineral soil 5 to 10 cm (%C) y = x x 2 adjusted r 2 = 0.30; p = Mineral soil 5 to 10 cm depth Time since fire (years) Sampled in 2003 Sampled in 1989 Sampled in 1985 Fig S1. Changes in soil organic carbon concentrations [% C = (g organic C/g dry soil)*100] in two mineral soil layers with time since stand-replacing wildfire. Points are means of 3 transects per site but variance estimates (+ 1 standard error) are available only for 2003 and some 1989 data (see Study sites and methods ). Sites sampled in multiple years are connected by solid black lines. Horizontal dashed lines bracket the range of values for at least 4 unburned sites using two standard errors centered on the mean. Thick solid black lines are the best-fit curve through all site means. Symbol colors identify whether sites were statistically different (P < 0.10) from an adjacent unburned site (white), not statistically different from an adjacent unburned site (grey), or not statistically compared to an adjacent unburned site (black).

5 III. References for Electronic Supplementary Material Abril M, Ferran A, Sabaté S, Sala A, Serrasolsas I (1987) Efectes dels incendis forestals en el bosc meiterrani: recuperació del sòl i de la vegetatió. Informe final. Caixa de Barcelona. Baeza MJ, Raventós J, Escarré A, Vallejo VR (2006) Fire risk and vegetation structural dynamics in Mediterranean shrubland. Plant Ecol 187: Canadell J, Riba M., Andrés P (1988) Biomass Equations for Quercus ilex L. in the Montseny Massif, Northeastern Spain. Forestry 61: Floret C, Galan M.J., Le Floc'h E, Rapp M, Romane F (1989) Structure, biomass and nutrient content of a Mediterranean Quercus ilex coppice. Acta Oecologica 10: Lledó, MJ (1982) Datos energéticos, estructurales y químicos de Pinus halepensis Mill. en el pinar de Sierra Espuña (Murcia). Tesis de Licenciatura. Universidad de Valencia.