Ecological restoration in mediterranean-type shrublands and woodlands

The Mediterranean-type ecosystems (further MTEs) are limited to five regions on Earth (Cowling et al. 1996): Mediterranean Basin, California, Central Chile, the Cape of South Africa and the Southwest (and partly South) Australia. These regions are characteristic of western ocean coastlines in warm-temperate latitudes characterized by descending water-deprived ethesial winds. They are invariably transitional between temperate forests and semi-deserts. Precipitation seasonality and prevalence of winter-rainfall/summer drought cycling are regular, although not exclusive to the MTEs (Blumler 2005; Rebelo et al. 2006). Fire has been part of the natural regeneration cycles and undoubtedly also evolutionary history of the scrublands and woodlands (perhaps except for the Chilean MTE) for millions of years. The Northern Hemisphere MTEs and the Central Chilean MTE are home to relatively young geologically and climatically dynamic landscapes. The MTEs of the African Cape and Australia are, on the other hand, geologically quiescent and climatically buffered – most of these regions qualify as Old Stable Landscapes (Hopper 2009; Mucina and Wardell-Johnson 2011). MTEs are evolutionary hotbeds and musea: they are home to several global centres of biodiversity (Myers et al. 2000) and have about 20 per cent of total floristic diversity in an area covering just 5 per cent of the land surface. Vegetation of the MTEs is typically sclerophyllous shrublands, however (pine, oak, eucalyptus) woodlands are also important. Besides the enormous biodiversity, the regions supporting MTEs have been under human pressure for a long time. Some (Mediterranean Basin and its eastern outposts in the Middle East) have been the cradle of agriculture and have seen the rise of many civilizations. Past and present human use put these ecosystems under pressure and where possible and feasible, restoration of these ecosystems emerged as one of the ways for their wise, future-oriented management. Each of the partial MTEs is exposed to multiple challenges of rehabilitation and a profound review of these is beyond the scope of this chapter. Therefore we have embarked on featuring the dominant rehabilitation focus in each MTE

Leaf physiological traits in relation to resprouter ability in the Mediterranean Basin

Abstract In Mediterranean ecosystems, fire is a strong selective agent among plants, and the different post-fire regeneration strategies (e.g. resprouting and non-resprouting) have implications for other plant traits. Because young plants of non-resprouters need to grow quickly and mature well before the next fire, we predict that they should possess leaf traits related to increased efficiency in growth and resource acquisition compared with resprouter species. To test this hypothesis, we measured specific leaf area, leaf nitrogen and carbon concentrations and leaf physiological traits, including gas exchange parameters and chlorophyll fluorescence, in 19 Mediterranean species cultivated in a common garden. Both cross-species and phylogenetically informed analyses suggest that non-resprouters have better physiological performance at the leaf level (i.e. higher photosynthetic capacity) than resprouters. All these results suggest that non-resprouter species are able to take greater advantage for vegetative growth and carbon fixation than resprouters during periods when water is readily available. The contrasted physiological differences between resprouters and non-resprouters reinforce the idea that these two syndromes are functionally different (i.e. they are functional types)

Post-drought conditions and hydraulic dysfunction determine tree resilience and mortality across Mediterranean Aleppo pine ( Pinus halepensis ) populations after an extreme drought event

International audienceAbstract Drought-related tree mortality is a global phenomenon that currently affects a wide range of forests. Key functional variables on plant hydraulics, carbon economy, growth and allocation have been identified and play a role in tree drought responses. However, tree mortality thresholds based on such variables are difficult to identify, especially under field conditions. We studied several Aleppo pine populations differently affected by an extreme drought event in 2014, with mortality rates ranging from no mortality to 90% in the most severely affected population. We hypothesized that mortality is linked with high levels of xylem embolism, i.e., hydraulic dysfunction, which would also lead to lower tree resistance to drought in subsequent years. Despite not finding any differences among populations in the vulnerability curves to xylem embolism, there were large differences in the hydraulic safety margin (HSM) and the hydraulic dysfunction level. High mortality rates were associated with a negative HSM when xylem embolism reached values over 60%. We also found forest weakening and post-drought mortality related to a low hydraulic water transport capacity, reduced plant growth, low carbohydrate contents and high pest infestation rates. Our results highlight the importance of drought severity and the hydraulic dysfunction level on pine mortality, as well as post-drought conditions during recovery processes

Factores bióticos y abióticos implicados en los procesos de decaimiento de bosques y matorrales mediterráneos secos y semiáridos

International audienc