Ramon Pérez-Obiol

Bio: Ramon Pérez-Obiol is an academic researcher from Autonomous University of Barcelona. The author has contributed to research in topics: Holocene & Vegetation. The author has an hindex of 16, co-authored 16 publications receiving 1313 citations. Previous affiliations of Ramon Pérez-Obiol include University of Barcelona.

Pollen‐based biome reconstruction for southern Europe and Africa 18,000 yr bp

Abstract: Pollen data from 18,000 C-14 yr sp were compiled in order to reconstruct biome distributions at the last glacial maximum in southern Europe and Africa. Biome reconstructions were made using the objective biomization method applied to pollen counts using a complete list of dryland taxa wherever possible. Consistent and major differences from present-day biomes are shown. F orest and xerophytic woods/scrub were replaced by steppe, both in the Mediterranean region and in southern Africa, except in south-western Cape Province where fynbos (xerophytic scrub) persisted. Sites in the tropical highlands, characterized today by evergreen forest, were dominated by steppe and/or xerophytic vegetation (cf. today's Ericaceous belt and Afroalpine grass land) at the last glacial maximum. Available data from the tropical lowlands are sparse but suggest that the modern tropical rain forest was largely replaced by tropical seasonal forest while the modern seasonal or dry forests were encroached on by savanna or steppe. Montane forest elements descended to lower elevations than today.

Palynological evidence for vegetational history in semi-arid areas of the western Mediterranean (Almería, Spain)

Abstract: Three sedimentary sequences from the southeastern littoral of the Iberian Peninsula have been palynologically studied. The results obtained show that during the Holocene no significant forest cover existed in the studied area, so that the different phases identified mainly show an alternation of shrub formations and steppe communities probably determined by limitations that are fundamentally bioclimatic. Highest values of arboreal pollen at the bottom of the San Rafael sequence would correspond to an older period, when the area appears to be dominated by shrub communities with a high proportion of wild olive, whereas at the beginnings of the Holocene it is dominated by steppe formations. Between 7000 and 4500 yr BP the Holocene optimum is recorded, with a significant degree of vegetational cover. This period ends abruptly with a radical transform ation of the landscape that reflects the establishment of the steppe conditions that persist today, which lead to the marginalization of the maquis and the impac...

Mid-Holocene vegetation and climatic history of the Iberian Peninsula

Abstract: The aim of this research is to study the climate and vegetation history in the western Mediterranean, in the Iberian Peninsula, during the middle Holocene through pollen analysis. The origin of the deposits varied from the most xeric to more mesic Mediterranean environments. The timing, extent, and progress of the establishment of the Mediterranean climate have a degree of variability depending on the biogeographical region. Analyses of several pollen sequences reveal climatic transformations in the flora and vegetation between 7000 and 4000 cal. yr BP. Pollen concentrations have been used in some sequences to evaluate the order of magnitude in biomass changes through time. Three main spatial and taxonomic responses could be assumed: (1) in littoral regions, deciduous broadleaf trees were frequently dominant and then replaced by sclerophyllous and evergreen forests; (2) in continental regions and sub-Mediterranean mountains, the dominance of pine throughout the whole Holocene signals a change of less magn...

Glacial refugia influence plant diversity patterns in the Mediterranean Basin

Abstract: Aim The aims of this study were to assess the distribution of putative Mediterranean refugia of plants, to compare the locations of refugia and those of regional hotspots of plant biodiversity, and to provide a critical analysis of the Mediterranean refugium paradigm. Furthermore, we consider how biogeographical and genetic results can be combined to guide global conservation strategies. Location The Mediterranean region. Methods We started from a detailed analysis of the scientific literature (1993-2007) in order to identify refugia in the Mediterranean region, based on intraspecific phylogeographical studies of plant species. We used population locations together with gene-pool identity to establish the database, comparing patterns of phylogeographical concordance with the locations of Mediterranean refugia. We then tested the biogeographical congruence between two biodiversity components, namely phylogeographical refugia and regional hotspots. Results We identified 52 refugia in the Mediterranean bioclimatic region and confirmed the role played by the three major peninsulas, with a shared total of 25 refugia. We emphasize the importance of areas that have previously been attributed a lesser role (large Mediterranean islands, North Africa, Turkey, Catalonia). Of the 52 refugia identified, 33 are situated in the western Mediterranean Basin and 19 in the eastern part. The locations of the phylogeographically defined refugia are significantly associated with the 10 regional hotspots of plant biodiversity, with 26 of these refugia (i.e. 50%) occurring within the hotspots. Main conclusions The locations of refugia are determined by complex historical and environmental factors, the cumulative effects of which need to be considered because they have occurred since the Tertiary, rather than solely during the last glacial period. Refugia represent climatically stable areas and constitute a high conservation priority as key areas for the long-term persistence of species and genetic diversity, especially given the threat posed by the extensive environmental change processes operating in the Mediterranean region. The refugia defined here represent 'phylogeographical hotspots'; that is, significant reservoirs of unique genetic diversity favourable to the evolutionary processes of Mediterranean plant species.

Geographic Range Size and Determinants of Avian Species Richness

Abstract: Geographic patterns in species richness are mainly based on wide-ranging species because their larger number of distribution records has a disproportionate contribution to the species richness counts. Here we demonstrate how this effect strongly influences our understanding of what determines species richness. Using both conventional and spatial regression models, we show that for sub-Saharan African birds, the apparent role of productivity diminishes with decreasing range size, whereas the significance of topographic heterogeneity increases. The relative importance of geometric constraints from the continental edge is moderate. Our findings highlight the failure of traditional species richness models to account for narrow-ranging species that frequently are also threatened.

Mid-Holocene and glacial-maximum vegetation geography of the northern continents and Africa

Abstract: BIOME 6000 is an international project to map vegetation globally at mid-Holocene (6000 14C yr BP) and last glacial maximum (LGM, 18,000 14C yr BP), with a view to evaluating coupled climate-biosphere model results. Primary palaeoecological data are assigned to biomes using an explicit algorithm based on plant functional types. This paper introduces the second Special Feature on BIOME 6000. Site-based global biome maps are shown with data from North America, Eurasia (except South and Southeast Asia) and Africa at both time periods. A map based on surface samples shows the method's skill in reconstructing present-day biomes. Cold and dry conditions at LGM favoured extensive tundra and steppe. These biomes intergraded in northern Eurasia. Northern hemisphere forest biomes were displaced southward. Boreal evergreen forests (taiga) and temperate deciduous forests were fragmented, while European and East Asian steppes were greatly extended. Tropical moist forests (i.e. tropical rain forest and tropical seasonal forest) in Africa were reduced. In south-western North America, desert and steppe were replaced by open conifer woodland, opposite to the general arid trend but consistent with modelled southward displacement of the jet stream. The Arctic forest limit was shifted slighly north at 6000 14C yr BP in some sectors, but not in all. Northern temperate forest zones were generally shifted greater distances north. Warmer winters as well as summers in several regions are required to explain these shifts. Temperate deciduous forests in Europe were greatly extended, into the Mediterranean region as well as to the north. Steppe encroached on forest biomes in interior North America, but not in central Asia. Enhanced monsoons extended forest biomes in China inland and Sahelian vegetation into the Sahara while the African tropical rain forest was also reduced, consistent with a modelled northward shift of the ITCZ and a more seasonal climate in the equatorial zone. Palaeobiome maps show the outcome of separate, independent migrations of plant taxa in response to climate change. The average composition of biomes at LGM was often markedly different from today. Refugia for the temperate deciduous and tropical rain forest biomes may have existed offshore at LGM, but their characteristic taxa also persisted as components of other biomes. Examples include temperate deciduous trees that survived in cool mixed forest in eastern Europe, and tropical evergreen trees that survived in tropical seasonal forest in Africa. The sequence of biome shifts during a glacial-interglacial cycle may help account for some disjunct distributions of plant taxa. For example, the now-arid Saharan mountains may have linked Mediterranean and African tropical montane floras during enhanced monsoon regimes.