Über die Vegetation der Bermuda-Inseln II. Pflanzengesellschaften von Wäldern, Rasen und in Hackfrucht-Beständen mit einem Vergleich mit entsprechenden Assoziationen anderer Gebiete
[On the vegetation of the Bermuda Islands. II. Plant communities of woodlands, of grasslands and in crop stands, with comparisons with vicariant vegetation in other regions]
Most of the acreage of the main islands of Bermuda consists of sites with the potentiality of the development of woodlands in terminal successional stages. But in present times, such woodlands occupy small percentages of the islands only, mainly due to anthropogenic influences. The evergreen Coccoloba uvifera woodlands grow on sites relatively near to the coast. The subassociation with Conocarpus and Paspalum vaginatum forms stands, only 4-7 m tall, bordering on mangrove vegetation. The subassociation with Sabal and Oplismenus, occcurring mostly in greater distance of the coast, can be taller (up to 12 m). The evergreen broad-leaved woodlands in the interior of the main islands are composed partly of Sapindales (e. g., Elaeodendron laneanum, Dodonaea, Rhus, Cardiospermum) and of Myrtaceae (e. g., Eugenia and the presumably introduced Pimenta). These woodlands became very restricted in acreage under anthropogenic influences, resulting also in extermination of a number of their characteristic species. The remaining stands are mostly interspersed with species, proved or assumed to be adventitious. The endemic conifer Juniperus bermudiana, a typical pioneer species, can be important in initial or intermediate stages of successions terminating with these broadleaved woodlands. But on certain dry sites, Juniperus bermudiana can apparently persist as dominant of terminal stages. Of the grassland vegetation treated here, communities dominated by Stenotaphrum secundatum are connected syndynamically with the Coccoloba uvifera woodlands. They can form early stages of successions terminating with these woodlands, or can replace them after their destruction by natural or anthropogenic influences. The Dichondra-Cynodon grassland constitutes, in optimal conditions, lawns in park lands or gardens. It forms a dense turf composed of several species, mainly not indigenous on the Bermudas, mostly of tropical, partly also of temperate origin. The community with the dominant adventitious Panicum maximum forms tall-grass stands, partly more than 2 m high. It grows at places rather protected from treading, but under conditions preventing the dominance of shrubs and lianas (mainly by occasional cutting). Among the several weed communities developed on the Bermudas since more than 350 years, only the Bidens pilosa-Euphorbia hypericifolia association is treated here. It consists of species with mostly tropical-subtropical affinities, but also of some mainly temperate taxa, e. g., Sonchus oleraceus. This plant community grows between crops on fertile upland soils (mainly latosols). In a discussion, the remarkably northern extension of vegetation with tropical affinities on the Bermudas is emphasized. The edaphical and syndynamical relations between the Juniperus bermudiana woodlands and the broad-leaved evergreen woodlands of the Bermudas are compared with similar connections of coniferous forests (with Pinus or Juniperus) and broad-leaved woody vegetation in other subtropical or tropical border areas. The relatively small height of the indigenous Bermudan trees coincides with analogous behaviour of tree growth on certain other isolated islands, e. g. the Hawaiian Islands and the Ryukyu Islands in the Pacific Ocean regions.