Tertiary relict trees in a Mediterranean climate: abiotic constraints on the persistence of Prunus lusitanica at the eroding edge of its range

Abstract

Aim To investigate the ecophysiological traits allowing persistence of a subtropical relict tree (Prunus lusitanica L.) under a dry Mediterranean climate at the eroding edge of its range.Location A glasshouse for the study under controlled conditions and two marginal populations located in riparian forests of central Spain and exposed to summer drought, in contrast to subtropical populations that grow in mountain cloud forests.Methods Two experiments were conducted to assess tolerance to the abiotic conditions found in riparian habitats. In a glasshouse experiment, gas-exchange and light-use parameters were measured to evaluate seedling responses to a factorial combination of irradiance (60%, 10%, 2% and 0.5% full sun) and moisture (well watered control and drought stress). In a parallel field experiment, irradiance and soil moisture were measured as predictors of seedling survival at two sites in which half the seedlings were subjected to a threefold increase in summer precipitation by adding water every 10 days.Results Soil moisture strongly determined survival both in the glasshouse and in the two field sites. In the field, periodic addition of water failed to increase survival. Water-use efficiency (WUE) increased with drought. Seedlings did not tolerate deep shade (2-0.5%) and their performance and survival were better when exposed to moderate (10%) or high (60%) irradiance. The effect of water stress on seedling performance was stronger at moderate irradiance, moderate at high irradiance and negligible at very low light. Seedling size (height and number of leaves) attained after 1 month of experimental treatments had a positive effect on survival at the end of the summer, hence greater survival was not achieved at the expense of vertical growth.Main conclusions While studies in Macaronesia have shown that P. lusitanica occupies a wide range of moisture conditions along mountain slopes, it behaves as an obligate riparian species in dry peripheral populations. Intolerance to deep shade and tolerance to moderate and high irradiance allow the species to grow in small and moist gaps, or in treeless river sections. Despite the species' low range filling in marginal, drought-prone regions, long-term persistence might have been achieved through shifts to riparian habitats serving as local refuges.

Fine-scale spatial patterns of the Tertiary relict Zelkova abelicea (Ulmaceae) indicate possible processes contributing to its persistence to climate changes

“…In the case of the extant Mediterranean flora, many ancient taxa evolved during the Cenozoic, well before the typical Mediterranean climate regime was established (Pulido et al 2008). A number of Tertiary relict taxa evolved from lineages that thrived under warm temperate (fully humid or winter dry) climates during most parts of the Cenozoic.…”

“…In contrast to the Cenozoic climate, today, these taxa have to cope with summer dry and hot conditions typical of the Mediterranean climate. As a result, these climate relict trees invariably exhibit highly fragmented ranges and low population sizes in southern Europe (Pulido et al 2008). Zelkova abelicea is such a relict species, persisting in a few sites in the island of Crete.…”

Marginal fragmented beech stands and climate change in Sicily: effects of non-sustainable traditional silviculture practices in relation to micro-topographic gradient

“…Barbeta et al (2011) mostrano risultati simili confrontando boschi frammentati e formazioni forestali continue al limite SE dei boschi di faggio della Spagna. Considerando che anche questi popolamenti di faggio si rinvengono al loro limite Sud-occidentale, in aree particolarmente soggette ai trend di aumento della temperatura, così come le nostre aree di studio delle Madonie (vedi Fig.2c), è evidente il rischio dell'aumento della marginalità ecologica, la progressiva riduzione del successo dei processi di rinnovazione (Jump et al, 2007;Pulido et al, 2008;Wagner et al, 2010), e il generale declino della specie (Piovesan et al, 2008).…”

Effects of traditional coppice practices and microsite conditions on tree health in a European beech forest at its southernmost range

“…Similar results were reported by Barbeta et al (2011), who compared fragmented and continuous forests at the edge of the species' range in southeastern Spain. However, the projected increasing temperatures in the Mediterranean region are likely to reduce the frequency of successful seedling establishment (Jump et al 2007, Pulido et al 2008, Wagner et al 2010, possibly leading to a general decline and local extinction (Piovesan et al 2008).…”

“…The Sicilian beech forests cover 15 924 ha (Camerano et al 2011) and are of particular phytogeographic and ecological interest (Gentile 1969, Raimondo et al 1992, Brullo et al 1999. Beech grows from 1200 up to 2000 m a.s.l.…”