The physical characteristics of the soil at the root–soil interface are crucial because they determine both physical aspects of root function such as water and nutrient uptake and the microbial activity that is most relevant to root growth. Because of this we have studied how root activity modifies the structure and water retention characteristic of soil adjacent to the root for maize, wheat and barley. These plants were grown in pots for a 6-week growth period, then the soil adjacent to the root (rhizosphere soil) and bulk soil aggregates were harvested. These soil aggregates were then saturated and equilibrated at matric potentials between ~600 kPa and saturation, and the water retention characteristics were measured. From subsamples of these aggregates, thin sections were made and the porosity and pore-size distributions were studied with image analysis. Both image analysis and estimates of aggregated density showed that the rhizosphere soil and bulk soil had similar porosities. Growing different plants had a small but significant effect on the porosity of the soil aggregates. Image analysis showed that for all the plant species the structure of the rhizosphere soil was different to that of the bulk soil. The rhizosphere soil contained more larger pores. For maize and barley, water retention characteristics indicated that the rhizosphere soil tended to be drier at a given matric potential than bulk soil. This effect was particularly marked at greater matric potentials. The difference between the water retention characteristics of the bulk and rhizosphere soil for wheat was small. We compare the water retention characteristics with the data on pore-size distribution from image analysis. We suggest that differences in wetting angle and pore connectivity might partly explain the differences in water retention characteristic that we observed. The impact of differences between the water retention properties of the rhizosphere and bulk soil is discussed in terms of the likely impact on root growth

Citation for published item:wqovernD F rF nd ¡ esteinssonD yF nd pririkssonD eF nd ghurhD wF tF nd vwsonD sF F nd impsonD sF eF nd iinrssonD eF nd hugmoreD eF tF nd gookD qF F nd erdikrisD F nd idwrdsD uF tF nd homsonD eF wF nd edderleyD F F nd xewtonD eF tF nd vusD qF nd idvrdssonD F nd eldredD yF nd hunrD iF @PHHUA 9vndspes of settlement in northern selnd X historil eology of humn impt nd limte )utution on the millennil sleF9D emerin nthropologistFD IHW @IAF ppF PUESIF Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. T H O M A S H . M c G O V E R N , O R R I VÉ S T E I N S S O N , A D O L F F R I -D R I K S S O N , M I K E C H U R C H , I A N L AW S O N , I A N A . S I M P S O N , A R N I E I N A R S S

One little understood aspect of the settlement and colonisation of Iceland is fuel resource use. In this paper we identify fuel ash residues from temporally constrained middens at two contrasting settlement age sites in Mývatnssveit, northern Iceland, one high status, the other low status and ultimately abandoned. Fuel residues derived from experimental combustion of historically defined fuel resources are used to provide control for thin section micromorphology and complementary image analyses of fuel residue materials found in the midden deposits. The results suggest that fuel resources utilised at the time of settlement were for both low temperature and high temperature use, and included a mix of birch and willow wood, peat, mineral-based turf and cow dung. There are, however, marked variations in the mix of fuel resources utilised at the two sites. This is considered to reflect social regulation of fuel resources and socially driven changes to local and regional environments that may have contributed to the success or failure of early settlement sites in Iceland.

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