Differences in the vegetation of the North Iberian Peninsula during the last 16,000 years

The dynamics of vegetation in the North Iberian Peninsula have been historically established from peaty and lacustrine records obtained in strongly continental mountainous areas. Pollen records located in areas with a more oceanic climate, have allowed a more precise evaluation of the changes and differences in the vegetation development of the various biogeographical areas in the North Iberian Peninsula, during the Late-glacial and Holocene. It was found that: (1) The vegetation of the Cantabrian–Atlantic province in northern Iberian Peninsula responded to climatic changes during the last 16000 years. (2) Tree vegetation declined during the Oldest Dryas, with steppe vegetation in the interior and cryophilous vegetation along the coast. (3) During the time of the Lateglacial Interestadial, lowlands, arboreal vegetation was dominant in the landscape (Pinus, Betula, Quercus, Corylus). (4) During the Younger Dryas the differences between coast and interior are less obvious. (5) During the Holocene oceanic decidious forests of Quercus robur, Corylus avellana, Tilia sp. and Fagus sylvatica were present along the coast. At low altitudes, in the interior, forests of Quercus robur / pyrenaica, enclaves of pine woods and Mediterranean types of forest (Quercus ilex, Olea europea) were present. At higher altitudes Pinus (P. sylvestris and P. uncinata) or mixed forests of Pinus and Betula were dominant.     

Steppes, savannahs, forests and phytodiversity reservoirs during the Pleistocene in the Iberian Peninsula

A palaeobotanical analysis of the Pleistocene floras and vegetation in the Iberian Peninsula shows the existence of patched landscapes with Pinus woodlands, deciduous and mixed forests, parklands (savannah-like), shrublands, steppes and grasslands. Extinctions of Arctotertiary woody taxa are recorded during the Early and Middle Pleistocene, but glacial refugia facilitated the survival of a number of temperate, Mediterranean and Ibero-North African woody angiosperms. The responses of Iberian vegetation to climatic changes during the Pleistocene have been spatially and temporarily complex, including rapid changes of vegetation in parallel to orbital and suborbital variability, and situations of multi-centennial resilience or accommodation to climatic changes. Regional characteristics emerged as soon as for the Middle Pleistocene, if not earlier: Ericaceae in the Atlantic coast indicating wetter climate, thermo-mediterranean elements in the south as currently, and broad-leaf trees in the northeastern. Overall, steppe landscapes and open Pinus woodlands prevailed over many continental regions during the cold spells of the Late Pleistocene. The maintenance of a high phytodiversity during the glacials was linked to several refuge zones in the coastal shelves of the Mediterranean and intramountainous valleys. Northern Iberia, especially on coastal areas, was also patched with populations of tree species, and this is not only documented by palaeobotanical data (pollen and charcoal) but also postulated by phylogeographical models.     

The Cenozoic vegetation of the Iberian Peninsula: A synthesis

The aim of this work is to provide a first approach to the evolution of Iberia's vegetation during the Cenozoic (with the exclusion of the Quaternary). The Palaeogene was floristically defined by Palaeotropical elements forming tropical/subtropical rainforests, mangrove swamps, edaphically-mediated laurophyllous forests and leguminous-sclerophyllous communities. During the Miocene, Iberian landscapes were drastically modified due to geographic and climatic changes (mainly cooling and aridification) changes. Open, steppe-like environments developed towards the interior of the peninsula and Arctotertiary elements invaded mountainous and riparian ecosystems, coexisting with or becoming part of evergreen, broadleaved forests of Palaeotropical species. From the Late Miocene onwards these forests suffered changes due to the extinction of taxa, the impact of environmental change on the survivors, and the perturbations caused by the arrival of further Arctotertiary elements. However, several Palaeotropical taxa overcame the environmental and climatic changes of the Miocene and Pliocene to form a part of the modern flora of the Iberian Peninsula.     

Anthracological evidence suggests naturalness of <Emphasis Type="Italic">Pinus pinaster</Emphasis> in inland southwestern Iberia

The study of well-preserved archaeological charcoals in the pre-Roman Iron Age settlement of Castillejos II (Badajoz, Spain) is used to reconstruct environmental conditions and land-use practices in vegetation landscapes in the southwest of the Iberian Peninsula before the arrival of Roman civilization. The results support that, while evergreen Quercus forests dominated during the Holocene, Pinus pinaster existed as a natural element of southwestern Iberian Peninsula vegetation. Although its presence could be linked to anthropogenic disturbance or fire history, it is suggested that P. pinaster populations survived during the Holocene in the region, mixed with oaks or in monospecific stands in mountain enclaves. This hypothesis contrasts with previous assumptions that P. pinaster was not autochthonous in the area.     

The influence of abrupt climate change on the ice‐age vegetation of the Central American lowlands

Aim To investigate the effects of abrupt climate change in the North Atlantic on the vegetation history of lowland Central America. We use palynological evidence from a Central American lake on the Yucatan Peninsula to evaluate the effects of rapid climate changes during the last ice age, between 65 and 8 ka. Location Lake Petén‐Itzá, lowlands of northern Guatemala. Methods Sediment core PI‐6 was sampled at c. 170‐year resolution for pollen and charcoal analysis in order to construct a temporal sequence of environmental change. Uni‐ and multivariate statistical analyses were performed on the pollen dataset to test whether there was an association between Heinrich events in the North Atlantic and vegetation changes in the Central American lowlands. Results Pollen analysis revealed that the composition of plant assemblages on the Yucatan Peninsula varied in phase with rapid changes in North Atlantic climate. Pine savannas were the main vegetation type between c. 60 and 47 ka. These savannas gave way to pine–oak (Pinus–Quercus) forests in the latter half of the last ice age. Marked episodes of replacement of the pine–oak assemblage by xeric‐tolerant taxa occurred during Heinrich events. The Last Glacial Maximum (LGM) was characterized by mesic conditions. Main conclusions The pollen record from Lake Petén‐Itzá showed that vegetation changes associated with Heinrich events were more significant than those associated with the LGM. Each Heinrich event produced a characteristic shift towards xeric taxa. Although colder than Heinrich events, the LGM on the Yucatan Peninsula was relatively moist, and the presumed savannization of the landscape during the maximum cooling of the last glacial was not supported by our data. Our findings suggest alternative scenarios for plant diversification and genetic interchange during glacial times, and also indicate that vegetation in tropical continental settings was not as stable as previously thought.     

Floristic changes in the Iberian Peninsula and Balearic Islands (south-west Europe) during the Cenozoic

Aim  The aim of this work was to identify the main changes in the flora and vegetation of the Iberian Peninsula over the Cenozoic Era, to record the disappearance of taxa associated with these changes and to determine the influence of climate and human activity on these events.
Location  The Iberian Peninsula and Balearic Islands.
Methods  A critical review was made of the palaeobotanical literature with the aims of detecting patterns of floristic change and extracting information on the disappearance of different taxa over the Cenozoic. These data are viewed alongside the most recent data for the climate of this period. A critical analysis is made of the role of Palaeotropical and Arctotertiary taxa in the forest communities of the Iberian Peninsula throughout the Cenozoic.
Results  Although the Eocene–Oligocene transition was a time when many taxa disappeared, the most outstanding events occurred between the end of the Oligocene and throughout the Miocene. Substantial floristic changes took place over this period, including the disappearance of 177 Palaeotropical taxa. This was probably related to acute cooling and aridification; no evidence exists that the Messinian Salinity Crisis had any important effect in the Iberian Peninsula. The last great disappearance of Palaeotropical taxa (36 in total) ended in the Middle–Late Piacenzian; Arctotertiary taxa were most affected during the Pleistocene. The Lower–Middle Pleistocene transition, best represented by marine isotopic stages (MIS) 36–34 and 20–18 and characterized by a change in glacial cyclicity, was the time of the last notable disappearance of taxa.
Main conclusions  This work provides the first chronogram of extinctions for the Iberian flora, and records the disappearance of 277 taxa during the Cenozoic. A clear relationship was detected between the main climatic events and the latest appearances of the different taxa.     

Present and future extension of the Iberian submediterranean territories as determined from the distribution of marcescent oaks

The present work proposes new boundaries for the current submediterranean territories of the Iberian Peninsula, defining them at the smallest scale attempted to date. The boundaries proposed are not sharp divisions but somewhat ‘gradual’, reflecting the transitional nature of the territories they encompass. Climate change predictions were used to estimate how the distribution of these submediterranean regions might change in the near future. The maps constructed are based on the distribution of marcescent Quercus species—trees that characterise the submediterranean plant landscape where they form the main forest communities. To determine their climatic range, the distribution of different types of Iberian oak forest was represented in ‘climate diagrams’ (ordination diagrams derived from principal components analysis), both in terms of individual species and groups of species based on leaf ecophysiological type, i.e. marcescent (Submediterranean), sclerophyllous (Mediterranean), semideciduous (Mediterranean) and deciduous (Eurosiberian). The climate range of each type of forest was determined, and the means of representative climate variables are analysed by one way ANOVA. The variables differentiating the forest groups were also examined by discriminant analysis. The range of the climate variables found to be associated with the majority of marcescent forests was used to determine the distribution of territories throughout the Peninsula with the same conditions (i.e. whether marcescent forests were present or not), thus providing a map of the Iberian submediterranean territories. Predictions of climate change were used to investigate possible climate-induced modifications in the boundaries of these territories in the near future. The patterns obtained show dramatic reductions in the extension of the Iberian submediterranean environment. Submediterranean conditions will probably disappear from the areas where they currently reign, and it seems unlikely that any new, large submediterranean areas will form by displacement towards higher altitudes. The outlook for the unique submediterranean vegetation of the Iberian Peninsula is gloomy.

Waxing and waning of forests: Late Quaternary biogeography of southeast Africa

African ecosystems are at great risk. Despite their ecological and economic importance, long‐standing ideas about African forest ecology and biogeography, such as the timing of changes in forest extent and the importance of disturbance, have been unable to be tested due to a lack of sufficiently long records. Here, we present the longest continuous terrestrial record of late Quaternary vegetation from southern Africa collected to date from a drill core from Lake Malawi covering the last ~600,000 years. Pollen analysis permits us to investigate changes in vegetation structure and composition over multiple climatic transitions. We observe nine phases of forest expansion and collapse related to regional hydroclimate change. The development of desert, steppe and grassland vegetation during arid periods is likely dynamically linked to thresholds in regional hydrology associated with lake level and moisture recycling. Species composition of these dryland ecosystems varied greatly and is unlike the vegetation found at Malawi today, with assemblages suggesting strong Somali‐Masai affinities. Furthermore, nearly all semiarid assemblages contain low forest taxa abundances, suggesting that moist lowland gallery forests formed refugia along waterways during arid times. When the region was wet, forests were species‐rich and very high afromontane tree abundances suggest frequent widespread lowland colonization by modern high elevation trees. Furthermore, species composition varied little amongst forest phases until ~80 ka when disturbance tolerant tree taxa characteristic of the modern vegetation increased in abundance. The waxing and waning of forests has important implications for understanding the processes that control modern tropical vegetation biogeography as well as the environments of early humans across Africa. Finally, this work highlights the resilience of montane forests during previous warm intervals, which is relevant for future climate change; however, we point to a fundamental shift in disturbance regimes which are crucial for the structure and composition of modern East African landscapes.     

Vegetation-atmosphere interactions and their role in global warming during the latest Cretaceous

Forest vegetation has the ability to warm Recent climate by its effects on albedo and atmospheric water vapour, but the role of vegetation in warming climates of the geologic past is poorly understood. This study evaluates the role of forest vegetation in maintaining warm climates of the Late Cretaceous by (1) reconstructing global palaeovegetation for the latest Cretaceous (Maastrichtian); (2) modelling latest Cretaceous climate under unvegetated conditions and different distributions of palaeovegetation; and (3) comparing model output with a global database of palaeoclimatic indicators. Simulation of Maastrichtian climate with the land surface coded as bare soil produces high-latitude temperatures that are too cold to explain the documented palaeogeographic distribution of forest and woodland vegetation. In contrast, simulations that include forest vegetation at high latitudes show significantly warmer temperatures that are sufficient to explain the widespread geographic distribution of high-latitude deciduous forests. These warmer temperatures result from decreased albedo and feedbacks between the land surface and adjacent oceans. Prescribing a realistic distribution of palaeovegetation in model simulations produces the best agreement between simulated climate and the geologic record of palaeoclimatic indicators. Positive feedbacks between high-latitude forests, the atmosphere, and ocean contributed significantly to high-latitude warming during the latest Cretaceous, and imply that high-latitude forest vegetation was an important source of polar warmth during other warm periods of geologic history.     

Sessile oak forest plant community changes on the NE Iberian Peninsula over recent decades

Aims Our aims were 3-fold: (i) to determine whether global change has altered the composition and structure of the plant community found in the sessile oak forests on the NE Iberian Peninsula over the last decades, (ii) to establish whether the decline in forest exploitation activities that has taken place since the mid-20th century has had any effect on the forests and (iii) to ascertain whether there is any evidence of impact from climate warming.     

Predictive modelling of tree species distributions on the Iberian Peninsula during the Last Glacial Maximum and Mid-Holocene

This paper reports a bioclimatic envelope model study of the potential distribution of 19 tree species in the Iberian Peninsula during the Last Glacial Maximum (LGM; 21 000 yr BP) and the Mid-Holocene (6000 yr BP). Current patterns of tree species richness and distributions are believed to have been strongly influenced by the climate during these periods. The modelling employed novel machine learning techniques, and its accuracy was evaluated using a threshold-independent method. Two atmospheric general circulation models, UGAMP and ECHAM3 (generated by the Palaeoclimate Modelling Intercomparison Project, PMIP), were used to provide climate scenarios under which the distributions of the 19 tree species were modelled. The results obtained for these scenarios were assessed by agreement measure analysis; they differed significantly for the LGM, but were more similar for the Mid-Holocene.
The results for the LGM support the inferred importance of pines in the Iberian Peninsula at this time, and the presence of evergreen Quercus in the south. Important differences in the altitude at which the modelled species grew were also predicted. During the LGM, some normally higher mountain species potentially became re-established in the foothills of the Pyrenees. The warm Mid-Holocene climate is clearly reflected in the predicted expansion of broad-leaved forests during this period, including the colonization of the northern part of the Iberian Peninsula by evergreen Quercus species.     

Early Pleistocene vegetation change in upland south‐eastern Australia

Aim This study aims to improve our understanding of the late Cenozoic history of Australian rain forest and sclerophyll biomes by presenting a detailed pollen record demonstrating the floristic composition and orbital‐scale patterns of change in forest communities of upland south‐eastern Australia, during the Early Pleistocene. The record is examined in order to shed light on the nature of the transition from rain forest‐dominated ‘Tertiary’ Australian vegetation to open‐canopied ‘Quaternary’ vegetation. Location Stony Creek Basin (144.13° E, 37.35° S, 550 m a.s.l), a small, infilled palaeolake in the western uplands of Victoria, Australia. Methods A c. 40‐m‐long sediment core was recovered from the infilled palaeolake. Palynology was used to produce a record of changing vegetation through time. Multivariate analyses provided a basis for interpreting the composition of rain forest and sclerophyll forest communities and for identifying changes in these communities over successive insolation cycles. Results Early Pleistocene upland south‐eastern Australian vegetation was characterized by orbital‐scale, cyclic alternation between rain forest and sclerophyll forests. Individual intervals of forest development underwent patterns of sequential taxon expansion that recurred in successive vegetation cycles. Diverse rain forests included a number of angiosperm and gymnosperm taxa now extinct regionally to globally. Sclerophyll forests were also diverse, and occurred under warm and wet climate conditions. Main conclusions The Stony Creek Basin record demonstrates that as recently as c. 1.5 Ma diverse rain forests persisted in southern Australia beyond the modern continental range of rain forest. The importance of conifers in these rain forests emphasizes that they have no modern Australian analogue. Alternation in dominance between these forests and diverse, sclerophyllous open canopied forests was apparently driven by changes in seasonality, and may have been promoted by fire.     

Expected trends and surprises in the Lateglacial and Holocene vegetation history of the Iberian Peninsula and Balearic Islands

Recent, high-resolution palaeoecological records are changing the traditional picture of post-glacial vegetation succession in the Iberian Peninsula. In addition to the influence of Lateglacial and Early Holocene climatic changes, other factors are critical in the course of vegetation development and we observe strong regional differences. The floristic composition, location and structure of glacial tree populations and communities may have been primary causes of vegetation development. Refugial populations in the Baetic cordilleras would have been a source, but not the only one, for the early Lateglacial oak expansions. From Mid to Late Holocene, inertial, resilient, and rapid responses of vegetation to climatic change are described, and regional differences in the response are stressed. The role of fire, pastoralism, agriculture, and other anthropogenic disturbances (such as mining), during the Copper, Bronze, Iberian, and Roman times, is analysed. The implications of ecological transitions in cultural changes, especially when they occur as societal collapses, are discussed.     

Ecology of cryptogamic epiphytes and their communities in deciduous forests in mediterranean Spain

A distribution of the epiphytic bryophyte and lichen vegetation of deciduous forests from the centre and north of the supramediterranean belt from the Spanish Iberian Peninsula was established using numerrical (PCA, CCA) and traditional floristic characteristics. Four groups have been established in relation to several syntaxa. Derived by numerical classification, possible successional trends between the groups with respect to changes in moisture, light and diameter of the trees are described. Nevertheless, patterns with succession in epiphytic communities are very complex to establish.     

Faunal turnover of marine tetrapods during the Jurassic–Cretaceous transition

Marine and terrestrial animals show a mosaic of lineage extinctions and diversifications during the Jurassic–Cretaceous transition. However, despite its potential importance in shaping animal evolution, few palaeontological studies have focussed on this interval and the possible climate and biotic drivers of its faunal turnover. In consequence evolutionary patterns in most groups are poorly understood. We use a new, large morphological dataset to examine patterns of lineage diversity and disparity (variety of form) in the marine tetrapod clade Plesiosauria, and compare these patterns with those of other organisms. Although seven plesiosaurian lineages have been hypothesised as crossing the Jurassic–Cretaceous boundary, our most parsimonious topology suggests the number was only three. The robust recovery of a novel group including most Cretaceous plesiosauroids (Xenopsaria, new clade) is instrumental in this result. Substantial plesiosaurian turnover occurred during the Jurassic–Cretaceous boundary interval, including the loss of substantial pliosaurid, and cryptoclidid diversity and disparity, followed by the radiation of Xenopsaria during the Early Cretaceous. Possible physical drivers of this turnover include climatic fluctuations that influenced oceanic productivity and diversity: Late Jurassic climates were characterised by widespread global monsoonal conditions and increased nutrient flux into the opening Atlantic‐Tethys, resulting in eutrophication and a highly productive, but taxonomically depauperate, plankton. Latest Jurassic and Early Cretaceous climates were more arid, resulting in oligotrophic ocean conditions and high taxonomic diversity of radiolarians, calcareous nannoplankton and possibly ammonoids. However, the observation of discordant extinction patterns in other marine tetrapod groups such as ichthyosaurs and marine crocodylomorphs suggests that clade‐specific factors may have been more important than overarching extrinsic drivers of faunal turnover during the Jurassic–Cretaceous boundary interval.     

The European Far West: Miocene mammal isolation,diversity and turnover in the Iberian Peninsula

Aim To analyse the diversity dynamics of Miocene mammalian faunas in the Iberian Peninsula in order to determine whether the patterns are related to the dispersal of taxa from other areas into this region. Location Mainly the Iberian Peninsula, but two close geographical areas (Central Europe and the Eastern Mediterranean) are also considered in some of our calculations. Methods Genus‐level faunal lists for a total of 299 localities from the Iberian Peninsula, covering 10 successive biochronological units [Mammal Neogene (MN) zones] that span from the latest Early Miocene to the early Pliocene (about 17–4 Ma), were compiled. The dataset was expanded with a further 331 localities in Central Europe and the Eastern Mediterranean for the same time span. Next, a taxonomically standardized database was used to create composite faunal lists of micro‐ and macromammalian genera present during each MN zone. Separate genera‐by‐MN‐zone matrices for both micro‐ and macromammals were built for each region. Mean standing diversity as well as origination and extinction rates were calculated for the Iberian Peninsula, and their correlation with preservation rates is discussed. Simpson’s coefficient of faunal similarity with Central Europe and the Eastern Mediterranean was calculated in order to evaluate whether diversity patterns were related to changes in the affinity of the Iberian mammalian faunas with those of other regions. Results Diversity changes in the Iberian macromammalian faunas coincide with periods of increased faunal similarity with other regions, suggesting a relationship to the expansions and contractions of the geographical ranges of the constituent taxa. This pattern is not recognized for micromammals; that is, their diversity trends are not related to changes in geographical ranges. Main conclusions Climatic shifts result in expansions or contractions in the geographical ranges of macromammals, owing to changes in the distribution of their preferred habitats. The lower dispersal ability of micromammals results in a higher extinction risk when habitat fragmentation confines their populations to relatively small environmental patches. Hence, they are more severely affected by climatic changes. Our results thus emphasize the role of climatic forcing in mammalian biogeography and diversity.     

Determinant variables of Iberian Peninsula Aphodiinae diversity (Coleoptera, Scarabaeoidea, Aphodiidae)

Aim The aims of this paper are to examine diversity–variability patterns for species of Aphodiinae (Coleoptera, Scarabaeoidea, Aphodiidae) on the Iberian Peninsula, and to determine the factors that influence their geographic distribution. Location Iberian Peninsula (Spain and Portugal). Methods Data from 30 studies and their bibliographies on species of Iberian Peninsula Aphodiinae were compiled. The reliability of the inventories was evaluated using parametric species richness estimators. In addition, a further 11 variables related to rarity, geographic distribution, or phylogenetic diversity were considered. Diversity variables were analysed using principal components analysis to reduce the number of dependent variables. Subsequently, the effect of differences in locality size among the 30 studies was eliminated by calculating and retaining the residuals of the curvilinear relationship of each diversity variable with the area. Generalized linear models were used to examine the relationships between diversity and 17 environmental variables. The diversity variables and their residuals were also subject to trend surface analysis in order to identify the relevance of spatially structured variables that had not been considered. The contribution of explanatory variables was determined through hierarchical variance analysis. Results Principal components analysis of biodiversity variables revealed that most of the variability could be explained using three biodiversity indexes: BI1, correlated positively with species richness, widely distributed species, frequent species, abundant species, species occurring in North Africa, Europe and the Iberian Peninsula, and phylogenetic diversity; BI2, correlated positively with numbers of infrequent and African–Iberian species; and, BI3, correlated positively with numbers of endemic, non‐abundant, European, and Iberian‐restricted species. A latitudinal disjunction emerged in BI1, with maximum scores at the north‐western and southern corners, while maximum BI2 scores were found throughout the south, and maximum BI3 scores in the north‐west. For BI1, it was climate that had the greatest influence, followed by lithology, and livestock presence. Geographic variables were the most significant for BI2, followed by climate and livestock presence. Finally, for BI3, climate variables were the most important, while geography, lithology and livestock presence had some relevance. Main conclusions The relevance of geographic variables indicates that other unaccounted‐for factors that are spatially structured could possibly explain additional variation in Aphodiinae diversity. These factors may be historic in nature, relating to the species groups, namely the Ibero‐European and the Mediterranean or Afro‐Iberian. The northern pattern could reflect the fact that the Iberian Peninsula acted as a colonization route and as a refuge during the glacial/interglacial cycles, while the southern pattern could be a consequence of the connection between the Iberian Peninsula and North Africa during the Messinian crisis, and/or a historic relationship in common, related to human activity.     

Future changes and driving factors of global peak vegetation growth based on CMIP6 simulations

Accurate detection and attribution of changes in global peak vegetation growth at the annual scale are prerequisites for characterising the productivity of terrestrial ecosystems and developing strategies for the sustainable management of ecosystems. This study examined the long-term global normalised difference vegetation index during the baseline period (1982–2015) and found widespread greening in 70% of global vegetated areas in response to climate warming. However, climate change is not the only cause of global greening. The spatial variability in the response of global vegetation to environmental factors has not been well established. The Cubist model was used to investigate the relationship between peak vegetation growth and environmental variables. The results showed that 64% of the spatial variation in greening/browning can be explained by climate (including precipitation and temperature), followed by atmospheric components of nitrogen deposition and carbon dioxide concentration (17%), terrain properties (12%), and soil properties (7%). By incorporating future climate and atmospheric component projections from the Coupled Model Intercomparison Project Phase 6 into the model, enhanced vegetation greening was predicted globally, particularly in evergreen needle-leaf forests and grasslands, from 2081 to 2100. Many browning changes were predicted in evergreen and deciduous broadleaf forests, mixed forests, and around areas influenced by human land use. Overall, these findings reveal that environmental factors have relevant integrated impacts on vegetation dynamics under climate change and should be considered during the design of local mitigation and adaptation management strategies.     

European post-glacial forests: compositional changes in response to climatic change

Abstract. Multivariate analysis of an extensive palyno-logical database for Europe has enabled reconstruction of broad-scale vegetation history. Whereas many major features of present vegetation patterns were established early in the Holocene, floristic composition of the forests has changed continuously up to the present day. For example, although ‘mixed deciduous forests’ had reached approximately their present extent in northwest Europe by 8000 B.P., Tilia peaked in abundance in these forests during the middle post glacial, whereas Pinus was most abundant in these forests during the early post-glacial and Fagus increased in abundance only in recent millennia. Pollen-climate response surfaces for major pollen taxa show how their distribution and abundance patterns relate to contemporary climate. Past forest-compositional changes were responses to climatic changes, the nature of which can be inferred from pollen-climate response surfaces. Post-glacial climate changes have been different in magnitude and direction in different regions of Europe. For example, in recent millennia the vegetation changes indicate decreasing summer temperatures in northern Europe but increasing summer temperatures in the Mediterranean region. The way in which vegetation responded to past climatic changes gives insight into the likely response of vegetation to future climate changes induced by the ‘greenhouse effect’.     

Development and regional differentiation of the European vegetation during the Tertiary

The Tertiary vegetation of Europe evolved from paratropical to warm-temperate and temperate forms in response to a progressive, non-linear, climatic cooling. Its vegetational forms are composed mainly of two separate ecological units: the evergreen, laurophyll paleotropical geoflora and the deciduous, broad-leaved Arctotertiary geoflora. The development of the Tertiary climate and its interaction with the vegetation are convincingly indicated by the geoflora's migration; the changes in its composition; and the development of the Tertiary forest, swamp, and aquatic plant communities. The paleotropical geoflora is characterized in the upper Cretaceous to the upper Miocene by paratropical rain forest, subtropical rain and laurel forests, temperate laurel forests and edaphically-mediated formation of laurel-conifer forests. The Arctotertiary geoflora advanced into Europe in waves since the Paleocene and formed the basis for the Tertiary mixed mesophytic forests. These can be divided into warm-temperate rain forests, oak-hornbeamchestnut or mixed beech-oak-hornbeam forests, and edaphic formations such as bottomland and swamp forests. Beginning in the lower Cretaceous, the hydrophytic vegetation developed independently of the forest vegetation and formed very diverse herbaceous fresh water, swamp, salt water, and coastal formations. Considerable differences in composition allow to separate floral regions and provinces in Eurosiberia. Instead of three ill-defined floral regions in the Paleocene, there are four well-defined floral regions in the Pliocene. A Mediterranean region cannot be recognized, although Mediterranean (eumesogeic) floral elements appear in the Eocene/Oligocene and thereafter. The Mediterranean sclerophyll forests probably arose after the destruction of the laurophyll forests during the Pleistocene.