Otero I., Boada M., Badia A., Pla E., Vayreda J., Sabaté S., Gracia C.A., Peñuelas J. (2011) Loss of water availability and stream biodiversity under land abandonment and climate change in a Mediterranean catchment (Olzinelles, NE Spain). Land Use Policy. 28: 207-218.LinkDoi: 10.1016/j.landusepol.2010.06.002
In the north rim of the Mediterranean region, where forest cover is increasing as a result of land abandonment and temperatures are rising as a result of climate change, there is increasing interest for the effects of such changes on the runoff of water courses. This is a paramount issue for the conservation of many freshwater habitats and species. In this work we studied the effects of both an increase in forest cover after depopulation and land abandonment and an increase in temperature on the runoff of a Mediterranean catchment and on the aquatic and semi-aquatic fauna species of the stream (Olzinelles valley, NE Spain). Although in our simulation no decreasing trend in runoff is detected, the monthly runoff-rainfall ratio is now 15% lower than 30 years ago, a fact that may be attributed to a drier period rather than to the small afforestation experienced by the catchment in the last decades. Other factors such as increasing temperatures, changing rainfall patterns and increasing canopy cover are discussed. The observed decrease in the water flow has caused the disappearance of white-clawed crayfish (Austropotamobius pallipes), Mediterranean barbel (Barbus meridionalis), chub (Squalius cephalus), European eel (Anguilla anguilla), and southern water vole (Arvicola sapidus). Our results suggest that in a progressively warmer climate, and especially after land abandonment processes, management of Mediterranean mountain areas should be oriented towards an appropriate distribution of agrarian and forest land-covers in terms of water availability. Down to the stream scale, the pools that keep water throughout the year should be conserved and extended to enhance its potential to maintain aquatic and semi-aquatic species populations. © 2010 Elsevier Ltd.
Peñuelas J, Estiarte M, Prieto P, Sardans J, Jump A Moreno JM, Torres I, Cespedes B, Pla E, Sabaté S, Gracia CA (2010) Projected Climate Change Impacts on Biodiversity in Mediterranean Ecosystems. In Atlas of Biodiversity Risk. Eds. Settele J, Penev L, Georgiev T, Grabaum R, Grobelnik V, Hammen V, Klotz S, Kühn I. Pensoft Publishers. Sofia-Moscow. ISBN 978-954-642-446-4 (print) and ISBN 978-954-642-447-1 (e-book).
Peñuelas J, Estiarte M, Prieto P, Sardans J, Moreno JM, Torres I, Céspedes B, Pla E, Sabaté S, Gracia C (2008) Impacts on biodiversity of Mediterranean ecosystems. In Settele, J. et al. (eds.) (in prep.): Atlas of Biodiversity Risks - from Europe to the globe, from stories to maps. Pensoft, Sofia & Moscow (www.pensoftonline.net/alarm-atlas-info) pp.76-77.
Morales P., Sykes M.T., Prentice I.C., Smith P., Smith B., Bugmann H., Zierl B., Friedlingstein P., Viovy N., Sabaté S., Sánchez A., Pla E., Gracia C.A., Sitch S., Arneth A., Ogee J. (2005) Comparing and evaluating process-based ecosystem model predictions of carbon and water fluxes in major European forest biomes. Global Change Biology. 11: 2211-2233.LinkDoi: 10.1111/j.1365-2486.2005.01036.x
Process-based models can be classified into: (a) terrestrial biogeochemical models (TBMs), which simulate fluxes of carbon, water and nitrogen coupled within terrestrial ecosystems, and (b) dynamic global vegetation models (DGVMs), which further couple these processes interactively with changes in slow ecosystem processes depending on resource competition, establishment, growth and mortality of different vegetation types. In this study, four models - RHESSys, GOTILWA +, LPJ-GUESS and ORCHIDEE - representing both modelling approaches were compared and evaluated against benchmarks provided by eddy-covariance measurements of carbon and water fluxes at 15 forest sites within the EUROFLUX project. Overall, model-measurement agreement varied greatly among sites. Both modelling approaches have somewhat different strengths, but there was no model among those tested that universally performed well on the two variables evaluated. Small biases and errors suggest that ORCHIDEE and GOTILWA + performed better in simulating carbon fluxes while LPJ-GUESS and RHESSys did a better job in simulating water fluxes. In general, the models can be considered as useful tools for studies of climate change impacts on carbon and water cycling in forests. However, the various sources of variation among models simulations and between models simulations and observed data described in this study place some constraints on the results and to some extent reduce their reliability. For example, at most sites in the Mediterranean region all models generally performed poorly most likely because of problems in the representation of water stress effects on both carbon uptake by photosynthesis and carbon release by heterotrophic respiration (Rh). The use of flux data as a means of assessing key processes in models of this type is an important approach to improving model performance. Our results show that the models have value but that further model development is necessary with regard to the representation of the some of the key ecosystem processes. © 2005 Blackwell Publishing Ltd.
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