Summary 1 Community assembly is described for two contrasting high Arctic chronosequences representing glacial regression of up to 2000 years on Svalbard. The chronosequences included a nutrient-poor glacier foreland (Midtre Lovénbre) and a series of nutrientenriched islands (Lovén Islands) progressively released from below a tidewater glacier. 2 Soil development and community assembly paralleled proglacial sequences elsewhere but time scales were extended and mature vegetation types comprised species-poor prostrate communities. 3 Initial colonization by Cyanobacteria stabilized soil surfaces and raised nutrient status. Cyanobacteria formed the dominant ground cover (up to 34%) for 60 years, after when they declined. 4 Vascular plants established slowly and represented minor components of ground cover for the first 100 years. Earliest colonizers were often species with ectomycorrhizal associations , followed by mid-successional species that tended to disappear as ground cover increased. Some species present in the mature vegetation at the oldest sites, established only after 60+ years. 5 Species richness of vascular plants increased for c . 100 years, beyond when only occasional species were added. Bryophytes became increasingly dominant with time. 6 Soil development on the Midtre Lovénbre and Lovén Island chronosequences was similar after 100 years. Differences subsequently developed, with organic horizon depth, percentage organic matter and water content on the older Lovén islands significantly greater than at equivalent Midtre Lovénbre sites. This was associated with increased bryophyte cover but lower vascular plant species richness. One explanation is a slightly more favourable microclimate, coupled with nutrient input from nesting birds. 7 Communities progressively recruit from a limited pool of effectively dispersed species, each with particular ecological requirements that determine their point of entry into the community. A measure of determinism by default is suggested in the way communities assembled. 8 Under climate warming, in the absence of nutrient enrichment, community development will accelerate but will be constrained by nutrient limitations and a restricted species pool. Where nutrients are less limiting, acceleration towards a moss-dominated community is expected, with a lower species richness of vascular plants.

SummaryThroughout western Europe heathlands dominated by ericaceous subshrubs occur on poor soils. Mostly, these heaths have developed and have been maintained by human activities. Traditional management has perpetuated ecosystems of a low nutrient status in which plant succession is arrested. Traditional management has involved a complex interaction between grazing, arable cultivation and the use of turf and plant material from the heaths. This basic system occurs throughout the European heathlands but with local variants. This paper reviews and compares the various systems of heathland use and management with the aim of developing new methods to maintain these cultural landscapes.

Summary1 It is proposed that as a general rule primary community assembly by autotrophs is preceded by a previously unrecognized heterotrophic phase that may be instrumental in facilitating the establishment of green plants and consolidating the assembly process. 2 This heterotrophic stage, of variable duration, involves the allochthonous input of both dead organic matter and living invertebrates sufficient to allow the initial establishment of functioning communities comprised of scavenging detritivores and predators. 3 Evidence for deposition of such materials onto newly exposed land surfaces and the development of such animal communities is summarized for a variety of sites and substrates worldwide. 4 It is suggested that these heterotrophic communities conserve nutrients, particularly nitrogen, and facilitate the establishment of green plants.