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Abstract:
Investigations on the "floating meadows" (Paspalo-Echinochloetum) of the vârzea-
region of central Amazonia in the surroundings of Manaus were made from May 1967
until October 1968. The ecology of the dominating species Pasþalum reþens BERG, Pasþalum fasciculatum WILLD., Echinocltloa þoþstaclqta (H. B. K.) HITCCHKOCK, Leersia ltexandra
Swart (Fam. Gramineae) and diverse subsidiary species (Oryza þerennis Moench, Hymeachne amþlexicaalis (Rudge) Nens, Panicum chloroticum Nens (.Fam. Gramineae), Scirþus
cubensis Poepp Kunth. (Fam. Cyperaceae) etc., was studied in details.
Regarding Pasþalum reþens Berg, various floating and one terrestrial forms of growth
were observed. Further, quantitative investigations on primary production and the
development of populations of this species were made. As shown by 4 Pasþalum reþens-
populations which were growing under different environmental conditions, conclusions
on age and rapidity of growth of the population could be drawn from the relation
between quantity of stems and number of shoots.
The preliminary conditions for a "secondary colonization" of floating populations
by non-floating plants and the repercussions of such sort of colonization on the primary
populations are discussed.
The vârzea-waters are subdivided into 3 biotopes with regard to the floating vegetation, and the factors responsible for them are discussed:
l) Bank- and sedimentation-zones in the Solimões-Amazon.
Dominating species: Pasþalumfasciculatum, Pasþalum reþens, Echinocltloa poþstaclgta,
2) Vârzea lakes with high fluctuations of water level.
Dominating species: Pasþalum fasciculatum, Pasþalum. reþens, Echinocltloa þoþstachya.
Sometimes, however, as well all other mentioned species occur in masses. Biotope
richest in species.
3) Várzea lakes with relatively little fluçtuations of water level.
Dominating species: Leersia hexandra, Scirþus cubensis, Pasþalum reþens.
Both the current-region of the Solimões-Amazon as a biotope of its own and the
influence of black-water on the vegetation are discussed.
