Kebede A.S., Dunford R., Mokrech M., Audsley E., Harrison P.A., Holman I.P., Nicholls R.J., Rickebusch S., Rounsevell M.D.A., Sabate S., Sallaba F., Sanchez A., Savin C., Trnka M., Wimmer F. (2015) Direct and indirect impacts of climate and socio-economic change in Europe: a sensitivity analysis for key land- and water-based sectors. Climatic Change. 128: 261-277.LinkDoi: 10.1007/s10584-014-1313-y
Integrated cross-sectoral impact assessments facilitate a comprehensive understanding of interdependencies and potential synergies, conflicts, and trade-offs between sectors under changing conditions. This paper presents a sensitivity analysis of a European integrated assessment model, the CLIMSAVE integrated assessment platform (IAP). The IAP incorporates important cross-sectoral linkages between six key European land- and water-based sectors: agriculture, biodiversity, flooding, forests, urban, and water. Using the IAP, we investigate the direct and indirect implications of a wide range of climatic and socio-economic drivers to identify: (1) those sectors and regions most sensitive to future changes, (2) the mechanisms and directions of sensitivity (direct/indirect and positive/negative), (3) the form and magnitudes of sensitivity (linear/non-linear and strong/weak/insignificant), and (4) the relative importance of the key drivers across sectors and regions. The results are complex. Most sectors are either directly or indirectly sensitive to a large number of drivers (more than 18 out of 24 drivers considered). Over twelve of these drivers have indirect impacts on biodiversity, forests, land use diversity, and water, while only four drivers have indirect effects on flooding. In contrast, for the urban sector all the drivers are direct. Moreover, most of the driver–indicator relationships are non-linear, and hence there is the potential for ‘surprises’. This highlights the importance of considering cross-sectoral interactions in future impact assessments. Such systematic analysis provides improved information for decision-makers to formulate appropriate adaptation policies to maximise benefits and minimise unintended consequences. © 2015, Springer Science+Business Media Dordrecht.
Sperlich D., Chang C.T., Penuelas J., Gracia C., Sabate S. (2015) Seasonal variability of foliar photosynthetic and morphological traits and drought impacts in a Mediterranean mixed forest. Tree Physiology. 35: 501-520.LinkDoi: 10.1093/treephys/tpv017
The Mediterranean region is a hot spot of climate change vulnerable to increased droughts and heat waves. Scaling carbon fluxes from leaf to landscape levels is particularly challenging under drought conditions. We aimed to improve the mechanistic understanding of the seasonal acclimation of photosynthesis and morphology in sunlit and shaded leaves of four Mediterranean trees (Quercus ilex L., Pinus halepensis Mill., Arbutus unedo L. and Quercus pubescens Willd.) under natural conditions. Vc,max and Jmax were not constant, and mesophyll conductance was not infinite, as assumed in most terrestrial biosphere models, but varied significantly between seasons, tree species and leaf position. Favourable conditions in winter led to photosynthetic recovery and growth in the evergreens. Under moderate drought, adjustments in the photo/biochemistry and stomatal/mesophyllic diffusion behaviour effectively protected the photosynthetic machineries. Severe drought, however, induced early leaf senescence mostly in A. unedo and Q. pubescens, and significantly increased leaf mass per area in Q. ilex and P. halepensis. Shaded leaves had lower photosynthetic potentials but cushioned negative effects during stress periods. Species-specificity, seasonal variations and leaf position are key factors to explain vegetation responses to abiotic stress and hold great potential to reduce uncertainties in terrestrial biosphere models especially under drought conditions. © The Author 2015. Published by Oxford University Press.
Sánchez-Costa E., Poyatos R., Sabaté S. (2015) Contrasting growth and water use strategies in four co-occurring Mediterranean tree species revealed by concurrent measurements of sap flow and stem diameter variations. Agricultural and Forest Meteorology. 207: 24-37.LinkDoi: 10.1016/j.agrformet.2015.03.012
Drought limits tree water use and growth of Mediterranean trees. However, growth and water use strategies are rarely addressed simultaneously across species and drought conditions. Here, we investigate the link between stem diameter variations and sap flow in four co-existing Mediterranean trees (Pinus halepensis Mill., Quercus pubescens Willd., Quercus ilex L. and Arbutus unedo L.), under relatively wet (2011) and dry (2012) conditions. Continuous stem diameter variations were converted to basal area increment (BAI) and de-trended to estimate tree water deficit (δW), an indicator of stem hydration. P. halepensis and Q. pubescens showed the most and the least conservative sap flow density (JS) regulation under drought, respectively, with Q. ilex and A.unedo showing intermediate drought responses. All species, except A. unedo, showed some between-year variability in the environmental control of JS. Seasonal stem shrinkage in response to drought (i.e., increasing δW) and subsequent trunk rehydration after rainfall (i.e., decreasing δW) occurred in all species. Vapor pressure deficit (VPD) and soil moisture (θ) interacted to determine seasonal variation in δW. Interestingly, in the dry year, 2012, more species-specific differences were found in the responses of δW to θ and VPD. Across species, JS and δW began to decline at similar soil moisture thresholds, underpinning the tight link between JS and δW under varying drought conditions. Annual BAI decreased proportionally more than tree-level transpiration (JT) between the wet (2011) and the dry (2012) year, hence growth-based WUE (WUEBAI=BAI/JT) decreased for all species, albeit less acutely for P. halepensis. Overall, despite their contrasting leaf habit and wood type, the studied Mediterranean tree species show coordinated responses of transpiration, water storage dynamics and growth-based WUE which allow them to cope with seasonal and interannual drought. © 2015 Elsevier B.V.
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