Of the spontaneous alien species included into our database 64% grow in culture (for human and animal food, as ornamental plants), the rest have found their way into Tallinn through some other human activity (ruderals
Native species of the Rubiaceae and Asteraceae were common, but these were mainly small herbs and ruderal
species (Table 1).
known UAE species and many are ruderal
or segetal species found so far
The main species might be identified as ruderal
weeds because they showed early emergence, short life cycle, quick and profuse diaspore production and great resources allocation in reproductive structures (RADOSEVICH et al., 2007).
The main components in the pollen spectra are Pinus, Betula and Salix, and herbs, represented by ruderals
and undifferentiated herbs.
The dominance of ruderals
and generalists is typical of areas that are in the first stages of the recovery from a disturbance (Grime et al., 1988).
Among the weeds and ruderal
plants several field weeds were observed: corn cockle (Agrostemma githago), Centaurea cyanus, wild turnip (Brassica campestris), foxtail (Setaria sp.), black bindweed (Fallopia convolvulus), pale persicaria (Polygonum lapathifolium), cleavers (Galium aparine).
Still, the high proportion of Poaceae and the ruderal
(especially Urtica) pollen may have been facilitated by forest disturbance, attesting well with archaeological records of the colonization of the Vortsjarv Lowland during Mesolithic time (Jaanits 1968).
and introduced species are significantly more abundant at SCP.
The model of Grime (1977), analyzed by Brzeziecki and Kienast (1994) using multivariate statistical methods, distinguishes three major groups and intermediates: the ruderal
(R), the stress tolerant (S), and the competitive (C) strategies.
Both annual ruderals
and long-lived perennials have buffering systems for short-term variation in current seed supply.
Many higher elevation ruderals
of the Ru'us alJibal are absent in the Hajar Mountains, including the Jebel Akhdar