Summary1 Classifying species by shared functional characteristics is important if common functional response groups are to be identified among different taxa. 2 We investigated plant traits that determine the response of forest plant species to land use changes using literature data. Sources from eight European countries and four North-eastern American states, comprising 20 field studies yielded information on 216 forest plant species. For these species, data on 13 life history traits were collected. 3 Trait correlation structure was similar in the European and American data-sets and corresponded well to those described in the literature. The European and American herbs and the European graminoids were clustered into distinct emergent groups based on their plant traits. The profiles of the European and American emergent groups were similar. 4 Herb species belonging to emergent groups characterized by low dispersability (i.e. large seeds, low fecundity, unassisted dispersal) were relatively slow colonizers. Dispersability (and not recruitment) seems to be a key factor limiting the colonization of some forest plant species. The relationship between dispersability and colonizing capacity was less clear for graminoids. 5 A life history trait-based approach offers good opportunities to gain insight into the mechanisms behind species response to land-use change.

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Aim and location The research investigated the long-term effects of human disturbance, namely nineteenth century agricultural land-use, on the modern species composition, structure and distribution of Rich Mesic Forests (RMF) in western Massachusetts, USA. RMF are a species-rich north-eastern variant of the Mixed Mesophytic Forest Type of eastern North America.Methods Land-use history patterns were reconstructed for two towns (c. 16,000 ha) from the onset of widespread European settlement and agricultural land-use in the late eighteenth century until present. Vegetation and a range of environmental variables were sampled in sixty-one 10 · 10 m plots in thirty-four forest stands with varying histories of human disturbance. Vegetation data were ordinated (DCA) to identify patterns of variation and related environmental and historical factors. The distribution patterns of individual taxa in relation to historical land-use and environmental factors were analysed using G-tests of independence and logistic regression. Associations between species secondary forest colonization ability and life history characteristics (e.g. diaspore dispersal mode, degree of vegetative spread) were assessed.Results Persistent compositional differences were documented between the vegetation of primary forests and post-agricultural, secondary forests indicating that distribution patterns for many plant species still reflect the open, agricultural environment of the nineteenth century, despite the current predominance of forest cover in the study area. A major factor driving modern vegetation patterns in RMF is the ability and rate of colonization by forest herbs. In particular, species with seeds lacking morphological adaptations for dispersal (barochores) and those which produce seeds with elaiosomes to encourage ant dispersal (myrmecochores) are less frequent in secondary forests. Environmental differences between primary and secondary forests, although present, appear to be less important in influencing species distribution patterns.Main conclusions Widespread agricultural land-use represents a novel disturbance in the naturally forested ecosystems of eastern North America with long-term impacts on plant community composition and structure. Many secondary forest sites that are environmentally suitable for RMF vegetation do not support the suite of plant species typical of this community type, apparently because of the dispersal limitations of certain forest herbs. These poorly dispersed herb taxa are well adapted for growth in stable forest ecosystems characterized by local, small-scale disturbance (e.g. gap-phase dynamics), yet are maladapted for rapid population recovery and recolonization following severe disturbance (e.g. agricultural land-use).