Recent decline in precipitation and tree growth in the eastern Mediterranean

Abstract

We present evidence of a recent drying in the eastern Mediterranean, based on weather and tree-ring data for Samos, an island of the eastern Aegean Sea. Rainfall declined rapidly after the late 1970s following trends for the entire Mediterranean and was associated with reduced tree-ring width in Pinus brutia. The most recent decline led to the lowest annual radial stem increment after the last 100 years (as far as records reach). As moisture availability decreased best correlations of tree growth with rainfall were obtained for progressively longer integration periods (1-2 years in moister periods, 5-6 years during the severe dryness of 20th century's last decades), suggesting increasing dependency in deep soil water. Such long-term integration periods of tree-growth responses to precipitation have not been reported before. They may reflect a tree-rooting pattern adapted to cope with even several successive dry years. In late summer 2000, moisture reserves became exhausted, however, and a substantial fraction of low altitude pines died, including some 80-year-old trees, which underlines the exceptional extent this trend had reached. Our findings provide empirical support for Intergovernmental Panel on Climate Change projections derived from global circulation models that the Mediterranean, its eastern basin in particular, should become drier as temperature rises, as was the case in the recent past.

Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

“…A reduced growth rate in response to declining water availability is a universally observed plant response (Kelliher et al, 1980;Osmond et al, 1987;Oberhuber et al, 1998;Sarris et al, 2007). In most GDEs rainfall and groundwater provide important supplies of water, and the ratio of rainfallto-groundwater uptake varies spatially and temporally.…”

Sudden forest canopy collapse corresponding with extreme drought and heat in a mediterranean-type eucalypt forest in southwestern Australia

“…Despite these adaptations, MTFs have been plagued by chronic stress during recent periods of protracted drought conditions (Carnicer et al 2011). This has translated to extensive crown dieback (Lloret et al 2004) and declines in both growth (Jump et al 2006;Sarris et al 2007) and tree health (Raftoyannis et al 2008) in the Mediterranean basin. Many dominant tree species within MTFs in the South-West of Western Australia (SWWA) have shown similar symptoms in recent decades (Archibald et al 2005;Auclair 1992;Hooper 2009), corresponding with a long-term decline in rainfall (Fig.…”

Growth response to climate and drought change along an aridity gradient in the southernmost Pinus nigra relict forests

“…Furthermore, drought effects on growth may be time-dependent. In Pinus 3 halepenis Sarris et al (2007) reported that the growth response to drought was 48 more extended under low soil moisture conditions than under less xeric situations.…”