Knowledge of historical fire activity tends to be focused at local to landscape scales with few attempts to examine how local patterns of fire activity scale to global patterns. Generally, fire activity varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesised sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In eastern and western North America and western Europe and southern South America, charcoal records indicate less-than-present fire activity from 21,000 to ~11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greaterthan-present fire activity from ~19,000 to ~17,000 cal yr BP whereas most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to ~13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8000 to ~2000 cal yr BP, Indonesia from 11,000 to 4000 cal yr BP, and southern South America from 6000 to 3000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the postglacial period. These complex patterns can be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load.

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Pollen, plant macrofossil and charcoal analyses of sediments from two Alaskan lakes provide new data for inferring Lateglacial and Holocene environmental change.

Analyses of pollen, microscopic charcoal, loss on ignition (LOI) and chironomids in the sediment of the small sub-alpine lake Kichikol (2541 m a.s.l.; 39°59'N, 73°33'E; Alay Range, Kyrgyzstan) provide new data to reconstruct the vegetational and lacustrine history during the past 6300 years. From 6300—5100 calibrated 14C years BP (cal. yr BP) semi-deserts with Chenopodiaceae and Ephedra and rather open Juniperus stands persisted around the lake. At 5100—4000 cal. yr BP dense Juniperus forest established. Around 4000 cal. yr BP the forest retreated and was probably restricted to north-facing slopes, as is the case today. Changes in the hydrology of Kichikol are inferred from lithological properties, pollen of aquatic plants and remains of aquatic invertebrates. The lacustrine development of Kichikol suggests a step-wise increase in humidity during the mid and late Holocene, with major shifts recorded at 5000 and 4000 cal. yr BP. At the beginning of the record Kichikol was a very shallow, possibly temporary pond. An initial rise in water-table is registered at c. 5000 cal. yr BP, followed by a second rise to near present levels at c. 4000 cal. yr BP. These hydrological shifts could be related to an increase of westerly moisture transport from the Mediterranean region as a consequence of a late-Holocene weakening of the Central Asian High and Indian monsoon systems. Moderate human impact in the region is recorded after 2100 cal. yr BP, as indicated by pollen of Plantago lanceolata-type and a slight increase of charcoal accumulation rates. Considering the general course of climate as well as human impact we conclude that the present forest composition is natural or quasi-natural.

Surface pollen deposition at five sites (Kichikol, Karakol, Nishneye and Verkhneye Ozero, and Bakaly) in four different forest types ( Juniperus , Picea, Juglans and mixed forests) in Kyrgyzstan have been investigated to assess the relationship between modern vegetation and pollen composition in order to calibrate the pollen representation. Vegetation surveys with an estimation of the tree-crown cover (%) were made in 10 m × 10 m plots to relate the vegetation to surface pollen of moss polsters. Correlation calculations show a close relationship between vegetation (tree-crown cover) and pollen for the Juniperus site (eg, r2 = 0.76 between crown cover and arboreal pollen, AP) and the Picea site ( r2 = 0.85), whereas the linkage is weaker at the Juglans site ( r 2 = 0.35) and in mixed forests ( r2 = 0.32). The results of the surface samples of moss polsters are compared and discussed with surface samples of lake sediments that were taken at the same locations. We use vegetational maps from around the lakes to discuss the link between vegetation and pollen at extra-local scales (800 m around the sites). These comparisons show that AP underestimates the effective tree cover around all sites, with in extreme cases densely forested areas corresponding to AP values as low as <60; 30%. We explain this finding by the prevalent background pollen load that derives from the dry lowland and slope steppes ( Artemisia, Chenopodiaceae, Poaceae). Our investigation may improve the reconstruction of Quaternary vegetation and climate history of these forest belts in Kyrgyzstan (Central Asia) on the basis of fossil pollen assemblages from mire and lake sediments. It provides new insights into the pollen reflection of forest isles (eg, on humid slopes or mountain tops) that are surrounded by continental steppes; a vegetational situation that may be used as an analogue for the conditions during the full glacial in Eurasia and Northern America.