a b s t r a c tA pollen diagram was prepared from Lake Almalou, a volcanic crater wetland located on the eastern flanks of the Sahand Volcanic Complex in NW Iran. The core provides a 3700-year record of human activity and environmental change in an upland region. We attempt to relate vegetation changes to both climatic change and historical events. Variations of anthropogenic pollen indicators suggest several phases of intensified human activities. Two strongly expressed agricultural phases are dated at about 2450-2220 cal BP (Achaemenid Empire) and 230-30 cal BP (collapse of Safavid Dynasty to the modern period). Historical rather than climatic events appear to be the main controlling factors for upland land-use dynamics. Fruticulture has been practiced in the region at least since the Iron Age, reaching its maximum importance 1500-1250 cal BP during the reign of Sassanid Empire; it declined by the time of Islamic conquest of Iran (651 AD). The Little Ice Age is tangibly recorded by higher lake water levels most probably due to both lower summer temperatures and higher annual precipitations. Low values of cereal-type and cultivated tree pollen during this period may indicate a change in the lifestyle from the cultivation of fields and orchards to a more nomadic life dominated by summer pasture. The modern period (1850 AD onwards) is characterized by expansion of agricultural activities to upland areas and intensified pastoralism.

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The chironomid species inhabiting a natural dead arm (the Pilet dead Arm), two artificial backwaters (the Saxy Dyke field and the Ranchier Dyke Field) and the main channel of the lower Rhoˆ ne River (South of France) were studied. A between-class (between-station) Correspondence Analysis (CA) showed that, on the scale of the alluvial plain, habitat is a major factor influencing the species assemblages. The assemblage composition on the transversal floodplain gradient was compared with existing data on assemblages from the main channel of the Garonne River (South of France) and three of its floodplain waters (two side arms and one oxbow lake). In order to work at the level of taxonomic determination commonly used in paleoecological studies, the overall dataset (lower Rhoˆ ne + Garonne) was analyzed to the genus level. The genus level analysis confirmed that chironomid assemblages can be used to characterize the connectivity of small waterbodies with the main river channel and 44 chironomid genera were classified according to their hydrological preferences (lentic habitat taxa, ubiquitous taxa and lotic habitat taxa). This classification was then applied to a paleoecological dataset from the Saint-Omer basin (North of France) in order to test the potential of chironomids for paleoecological studies on fluvial environments. The results presented here highlighted this potential and indicate that river chironomid assemblages can be used as descriptors for alluvial habitats, and allow researchers to evaluate the level of connectivity of these habitats with the main river channel during floods. River chironomid assemblages are a promising tool for reconstructing past hydrological changes and for obtaining information on paleoflood periodicity.

The chironomid subfossils from a single sediment core in the floodplain of the Aa river (Saint-Omer basin, Northern France) were analysed. This study was a pioneering attempt to use sedimentary chironomid assemblages and lithostratigraphic analysis to reconstruct the palaeoenvironment and the past hydrodynamic conditions in a river system during the mid-Holocene period. In this paper, a chironomid subfossil typology is proposed, based on the current scientific knowledge about the present distribution of chironomid species through the cross-section of a floodplain (from lotic to more lentic habitats). A hydrological status is attributed to 27 subfossil chironomid taxa (limnophilous taxa and rheophilous taxa) from the Saint-Omer sediment sample. Based on these chironomid hydrological statuses and in regard with the lithostratigraphic data, the dynamics of chironomid subfossil assemblages showed the occurrence of some fluctuations between periods with lower (lentic periods SMch-1, SMch-3 and SMch-5) and higher (lotic periods SMch-2 and SMch-4) Aa river discharge rates during the Late-Atlantic and Subboreal periods. The lotic periods were correlated with several climatic events known to have occurred during these periods in Europe. Several hypotheses are put forward and discussed, as to the potential relationships between the levels of precipitation and the hydrological conditions in the Saint-Omer basin. Although chironomid analysis in river systems is still in its developmental phase, the conclusions drawn from the present findings on subfossil chironomids show that these can provide a useful tool for palaeoenvironmental reconstruction purposes.

A pollen diagram was constructed for the earlyto mid-Holocene transition (ca.