We present quantitative reconstructions of regional vegetation cover in northwestern Europe, western Europe north of the Alps, and eastern Europe for five time windows in the Holocene [around 6k, 3k, 0.5k, 0.2k, and 0.05k calendar years before present (BP)] at a 1° 9 1° spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant-functional types and three land-cover types [evergreen trees, Correspondence: A.-K. Trondman, tel. + 46 (0)480 44 61 98, fax + 46 (0)480 44 73 40, Global Change Biology summer-green (deciduous) trees, and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen, and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k BP and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However, the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k, 0.5k, and 0.2k BP is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe, in particular Britain and Ireland. Furthermore, the relationship between summer-green and evergreen trees, and between individual tree taxa, differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance, when Pinus is dominant over Picea as pollen percentages, Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover-climate interactions, biodiversity and human resources.

Published by Copernicus Publications on behalf of the European Geosciences Union. 484M.-J. Gaillard et al.: Holocene land-cover reconstructions for studies on land cover-climate feedbacks Abstract. The major objectives of this paper are: (1) to review the pros and cons of the scenarios of past anthropogenic land cover change (ALCC) developed during the last ten years, (2) to discuss issues related to pollen-based reconstruction of the past land-cover and introduce a new method, REVEALS (Regional Estimates of VEgetation Abundance from Large Sites), to infer long-term records of past landcover from pollen data, (3) to present a new project (LAND-CLIM: LAND cover -CLIMate interactions in NW Europe during the Holocene) currently underway, and show preliminary results of REVEALS reconstructions of the regional land-cover in the Czech Republic for five selected time windows of the Holocene, and (4) to discuss the implications and future directions in climate and vegetation/land-cover modeling, and in the assessment of the effects of human-induced changes in land-cover on the regional climate through altered feedbacks. The existing ALCC scenarios show large discrepancies between them, and few cover time periods older than AD 800. When these scenarios are used to assess the impact of human land-use on climate, contrasting results are obtained. It emphasizes the need for methods such as the REVEALS model-based land-cover reconstructions. They might help to fine-tune descriptions of past landcover and lead to a better understanding of how long-term changes in ALCC might have influenced climate. The RE-VEALS model is demonstrated to provide better estimates of the regional vegetation/land-cover changes than the traditional use of pollen percentages. This will achieve a robust assessment of land cover at regional-to continental-spatial scale throughout the Holocene. We present maps of RE-VEALS estimates for the percentage cover of 10 plant functional types (PFTs) at 200 BP and 6000 BP, and of the two open-land PFTs "grassland" and "agricultural land" at five time-windows from 6000 BP to recent time. The LAND-CLIM results are expected to provide crucial data to reassess ALCC estimates for a better understanding of the land suface-atmosphere interactions.

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Palaeoecological studies are yielding fresh insights into slow forest ecosystem processes that are rarely observed using standard ecological methods, yet have major impacts on ecosystem function. Regional pollen data describe the broad features of the regional spread of trees but yield few insights into the processes of stand invasion and the facilitating role of disturbance. Pollen and charcoal data from small forest hollows are used to complement regional data in the study of the spread of Picea abies and Fagus sylvatica into southern Scandinavia during the last 4000 years. P. abies spread as a migrating front and preferentially invaded successional Betula stands, which had become particularly widespread in the region during the last 1000 years as a result of human activity. The spread of P. abies also closely tracked the changing area of suitable regional climate. The spread of F. sylvatica was more directly linked to anthropogenic activities and disturbance by fire prior to stand establishment. F. sylvatica preferentially invaded rich deciduous stand types that had declined in abundance during the last 2000 years. A recent range reduction of F. sylvatica can also be ascribed to human activity. The stand-scale palaeoecological data show how site conditions and disturbance are more important rate-limiting factors for F. sylvatica than for P. abies and help explain why F. sylvatica spread shows a patchy dynamic rather than the smoother migrating front of P. abies.

Summary1 Two palaeoecological data sets were used to study forest development in the boreo-nemoral zone of southern Sweden during the last 3000 years. Maps of forest types present in 1250 BC, AD 500 and today were compiled from regional pollen data and these were compared with 16 stand-scale pollen analyses. 2 The forest type maps showed a transition from mixed deciduous forest to coniferous forest consisting chie¯y of Picea and Pinus. The stand-scale studies recorded the same general development despite site-speci®c trends. A detrended correspondence analysis displayed the successional trends of the stand-scale sites. All stands moved away from the rich deciduous forest represented by Alnus, Corylus, Quercus and Tilia via Betula and Carpinus to Picea and Pinus forest or, in two stands, to Fagus forest. 3 A rate of change analysis covering the last 3000 years showed that the changes recorded from the last 150 years were the most rapid, but represented the culmination of a transformation that was initiated 850 years earlier. These recent changes completely overshadowed the previous record. 4 The regional maps recorded relatively high proportions of Pinus in the eastern part of the study area throughout the period under investigation. The stand-scale studies indicated that this area had a high ®re frequency, while the relatively recent increase in Pinus in south-west Sweden was better explained by anthropogenic in¯uences. The stand-scale data suggested that the regional role of Pinus had been overestimated in southern Sweden 5 Corylus, Quercus and Tilia were the major species in the former forests, but began a slow decrease in importance around AD 700. The increasing cereal pollen record was related to the decline of the deciduous forest component, suggesting that anthropogenic activity has been the major driving force in its loss. 6 The combination of regional-and stand-scale studies has provided new insights into forest pattern and process. The local records capture the essential features of the regional record of vegetation history, record forest composition more faithfully than regional sites, and additionally yield insight into processes such as ®res that have a regional signi®cance.