Shrub biomass accumulation and growth rate models to quantify carbon stocks and fluxes for the Mediterranean region

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The importance of shrub formations in the Mediterranean area both in terms of area occupied and carbon sequestered by them is currently being recognized. However, due to the lack of suitable models to estimate biomass accumulation and growth rate in this region, the carbon sequestered by these formations is not included when computing the total carbon stocks in aboveground biomass in Mediterranean forest ecosystems, according to the IPCC guidelines. The aim of the present study is to develop equations to predict biomass accumulation and growth rate for the main shrub formations in the region of Andalusia (Southern Spain), using the fraction of canopy cover (FCCm) and the average height of the shrub formations (Hm) as predictors. To build these models, more than 800 plots were inventoried using destructive sampling; the mean value found in the region for biomass accumulation and annual growth rate being 16.73 Mg ha−1 and 1.14 Mg ha−1 year−1, respectively. Heathers and big-size Cistaceae formations were the ones that presented the highest values of biomass accumulation (24.99 and 21.01 Mg ha−1, respectively), while the highest values for annual growth rate were achieved by Leguminous gorse shrubs and, again, big-size Cistaceae bushes (1.49 and 1.64 Mg ha−1 year−1, respectively). The carbon content for the main shrub species and formations in the area was also obtained. The developed models provide the opportunity to estimate shrub carbon stocks in Mediterranean forest management from easy-to-obtain variables, namely FCCm and Hm. Moreover, the used shrub formations classifications and model structure allow their applicability to compute biomass accumulation and growth rate at regional and national level using as input data from the Spanish National Forest Inventory. © 2015, Springer-Verlag Berlin Heidelberg.

This studied was carried out under the framework of the Project RECAMAN (Income and Capital of the Montes de Andalusia), funded by the Junta de Andalusia, through the Environment Agency and Water Andalusia, whose scientific officer has been Professor CSIC D. Pablo Campos Palacín. The authors acknowledge the unconditional support of all members of RECAMAN, especially to people who have provided us with information necessary for the completion of this work. Thus, it would highlight the collaboration of Luis Guzman and Isabel Martin from AMAyA and Francisca de la Hoz from Junta de Andalusia. On the other hand, the authors also thank the comments provided at various stages of work by Sven Mutke and two anonymous referees. The technical support of D. Roberto Vallejo Bombin (General Directorate of Rural Development and Forestry Policy, MAGRAMA) is also acknowledged. Milagros Serrano, Dr. Isabel Gonzalez and Purificación Pereira from the Laboratory of Ecology and Soils of CIFOR-INIA are also acknowledged for the care and rigor devoted in the determination of carbon in 123 species. Aurora Bachiller is acknowledged for the help provided in determining the age of the different shrub samples.

Peer reviewed