Seed rain in successional vegetation, Port Hills Ecological District, New Zealand

Patterns in vegetation and seed rain were measured in an abandoned agricultural scrubland/forest system in lowland Canterbury to test relationships between patterns of seed rain and succession in seral scrub and established low forest. indicator species analysis separated four distinct vegetation types which formed a successional chronosequence confirmed by air-photo interpretation and analysis of vegetation composition. Vegetation biomass (approximated by summed species importance scores) and species richness (mean species plot(-1)) both increased with successional stage. Although there was a significant difference in seed rain density among vegetation types, the relationship between seed rain and succession was clouded by individual species fecundity. There was a significant positive relationship between successional stage and seed rain species richness. The proportion of seed species present in seed rain but absent from extant vegetation was greater in less advanced vegetation. This relationship was determined by low species richness in the vegetation and a suite of highly mobile seed species, typical of more mature forest, common to all vegetation types. We conclude that forest recovery is not dispersal limited in the forest and seral scrub vegetation we investigated, and that with the continued absence of grazing pressure forest recovery should be rapid.