Effects of experimental warming and drought on biomass accumulation in a Mediterranean shrubland
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We studied the effects of experimental warming and drought on the plant biomass of a Mediterranean shrubland. We monitored growth at plant level and biomass accumulation at stand level. The experimentation period stretched over 7 years (1999–2005) and we focused on the two dominant shrub species, Erica multiflora L. and Globularia alypum L. and the tree species Pinus halepensis L. The warming treatment increased shoot elongation in E. multiflora, and the drought treatment reduced shoot elongation in G. alypum. The elongation of P. halepensis remained unaffected under both treatments. The balance between the patterns observed in biomass accumulation for the three studied species in the drought plots (reduction in E. multiflora and P. halepensis and increase in G. alypum) resulted in a trend to reduce 33% the biomass of the drought treatment plots with respect to the untreated plots, which almost doubled their biomass from 1998 to 2005. The results also suggest that under drier conditions larger accumulation of dead biomass may occur at stand level, which combined with higher temperatures, may thus increase fire risk in the Mediterranean area.
KeywordsBiomass accumulation Drought Elongation Erica multiflora Global warming Globularia alypum Mediterranean shrubland Pinus halepensis
We owe thanks to P. Bruna and G. Alessio for providing data and also to M. Ribera, B. González, V. Cruz, R. Marín, P. Mendoza, J. Muñoz, E. Quintanilla and N. Sanfeliu for their help in the collection of the data. We are especially grateful to J. Sardans for his valuable suggestions. This research was funded by the EU under the projects CLIMOOR (Contract ENV4-CT97-0694) and VULCAN (Contract EVK2-CT-2000-00094) and we also received additional financial help from the Spanish Government (grants CGL2006-04025/BOS and Consolider Montes CSD2008-00040), the Catalan Government (grant SGR2005-00312) and FP6 NEU NITROEUROPE (Contract GOCE017841).
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