Climate change over the Western Mediterranean and Atlantic Islands: a dendroclimatic and genetic survey of the genus Juniperus - MEDIATIC
Coordinator - Cristina Nabais
Programme - PTDC/AAC-CLI/103361/2008
Execution dates - 2010-01-01 - 2012-12-31 (36 Months)
Funding Entity - Fundação para a Ciência e Tecnologia (FCT)
Total Funding - 174 000 €
Proponent Institution -
Participating Institutions
Instituição Proponente
Principal Contractor
Faculdade de Ciências e Tecnologia da Universidade de Coimbra (FCT/UC)
Rua Sílvio Lima - Pólo II - Univ. Coimbra

Instituição Participante
Participating Institution
Fundação da Faculdade de Ciências (FFC/FC/UL)
Campo Grande - Edificio C7 -1º Piso

Unidade de Investigação
Research Unit
Centre for Functional Ecology/Centro de Ecologia Funcional (CFE)
Departamento de Botânica. Universidade de Coimbra

Unidade de Investigação Adicional
Additional Research Unit
Instituto Dom Luís (IDL/FUL/UL)
Departamento de Física da FCUL, Campo Grande, Edifício C8 - 6º Piso

Instituição de Acolhimento
Host Institution
Centre for Functional Ecology/Centro de Ecologia Funcional (CFE)
Departamento de Botânica. Universidade de Coimbra

In the last decades the Mediterranean climate has been subject of intense research. Its precipitation regime is characterized by strong seasonal behaviour as a result of a characteristic transition from mid-latitude to subtropical climates. Seasonal precipitation is also affected by strong inter-annual variability, which can be explained by a few large-scale atmospheric
circulation modes. The most prominent one is the North Atlantic Oscillation (NAO) that exerts maximum influence in precipitation over Iberia (Fig. 1) [1] and, to a less extent, over the Azores [2, 3]. Variations of precipitation on interannual and longer temporal scales have important impacts in agriculture, ecosystems, environment and socio-economics and water resources. Thus, efforts should be made to increase our understanding of long-term changes in precipitation and drought patterns and their links to controlling circulation influences. The accomplishment of such a task acquires more relevance within the framework of the recent climate change and future projected scenarios of more intense drought episodes in the Mediterranean region. Instrumental data provide a too short record to assess the recent climate trend in a longer temporal context and to deal with uncertainties in its regional manifestations. To solve this problem, climate-derived indicators (proxies) recorded in natural archives have been widely used to reconstruct past climate (Fig. 2) [4]. These natural records provide regional-scale information of several climate parameters (generally temperature and precipitation) with different temporal resolutions [5]. Therefore, to understand the regional impacts of climate change the compilation of a broad spatially distributed spectrum of high-resolution proxies is required. However, the majority of natural archives in extratropical regions come from continental areas, with small islands over the ocean remaining unexplored (Fig. 3). On the other hand, from a global climate perspective,
the regional information value contained in each proxy increases in regions with maximum responses to large-scale atmospheric patterns since they explain much of the global climate variability. Therefore, the exploration of new proxy records becomes of paramount importance in low-exploited areas that are especially sensitive to the main modes of atmospheric variability such as the NAO [6]. The Mediterranean area offers a wide spectrum of natural proxy records [5]. Among them, tree-ring information is probably the most important proxy for large areas around the Mediterranean (Fig. 4). Tree-ring records have a precise dating to the calendar year, which allows them to be compared directly with instrumental records and generally possess the highest correlations to instrumental climate data, compared with other proxies [7]. This provides a powerful tool for developing quantitative reconstructions of climate on century time scales. Several tree-ring based precipitation reconstructions have been developed in the Mediterranean, including Northern Africa (1,000 years) [8], eastern Mediterranean (400 years) [7] and northern Iberia (ca. 500 years) [9, 10, 11]. However, dendroclimate reconstructions from Atlantic islands have not been attempted yet, even when these regions are among those with the strongest NAO impact. The Atlantic islands, Azores and Madeira, are part of a phytogeographic region called Macaronesia that ranges across a considerable latitudinal and climatic gradient: from the cool-oceanic climate in Azores (40ºN) to the oceanic tropical climate in Cape Verde islands (15ºN), with the Mediterranean climates of Madeira and the Canaries in between. This area provides a
unique place to assess the Mediterranean climate variability, since Atlantic synoptic weather systems often impact in the archipelagos of Azores and Madeira before reaching the European continent. Several species of Juniperus occur in the Western Mediterranean and Atlantic islands [12] and it can function has a biogeographic and dendrochronological link between these
two areas. There has been little investigation into the impact of intraspecific genetic variability on tree ring climatic signal. The genus Juniperus contains species with a large number of subspecies or varieties that sometimes correspond to phenotypic adaptations to different climatic conditions [12]. A high genetic variability within populations can be a safer strategy for species growing under the variable Mediterranean climate. Whether physiological and growth differences among individuals of the same population can be related to overall genetic variability remains as an exciting open question. This proposal supposes an advance to optimize the selection of proxies over a region with high sensibility to large-scale climate variability. The results are expected to provide a more extended and representative dendrochronology network, a better regional understanding of the biological and climate variability and a potential contribution to past climate reconstructions.