Floristic Study of the Herbaceous Vegetation of Wet Lowlands in Aru Territory, Ituri Province (Democratic Republic of Congo)

Dieudonné UMA MUNDUA; Hippolyte NSHIMBA SEYA WA MALALE; Christophe LOMBA BOSOMBO; Prosper SABONGO; Roger KATUSI LOMALISA

Dieudonné UMA MUNDUA Laboratory of Plant and Animal Biology, Department of Biology–Chemistry, Institut Supérieur Pédagogique de Kisangani, Democratic Republic of Congo
Hippolyte NSHIMBA SEYA WA MALALE University of Kisangani, Faculty of Sciences, Laboratory of Ecology and Management of Plant Resources (LEGREV), P.O. Box 2012, Democratic Republic of Congo https://orcid.org/0009-0008-7555-1276
Christophe LOMBA BOSOMBO University of Kisangani, Faculty of Sciences, Laboratory of Ecology and Management of Plant Resources (LEGREV), P.O. Box 2012, Democratic Republic of Congo
Prosper SABONGO University of Kisangani, Faculty of Sciences, Laboratory of Ecology and Management of Plant Resources (LEGREV), P.O. Box 2012, Democratic Republic of Congo
Roger KATUSI LOMALISA University of Kisangani, Faculty of Sciences, Laboratory of Ecology and Management of Plant Resources (LEGREV), P.O. Box 2012, Democratic Republic of Congo

Keywords: flora, vegetation, humidity, phytosociology

Abstract

The study of plant communities was conducted using the Braun-Blanquet phytosociological method, supported by physiognomic, chorological, and numerical approaches. This phytosociological investigation aimed to inventory the biological diversity of wet lowlands in the eastern part of the Aru River watershed and to establish the ecological diagnostics of the surveyed herbaceous vegetation units. The wet lowlands studied constitute part of the water supply feeding the Aru River, one of the numerous tributaries of the Congo Basin in northeastern Democratic Republic of Congo (DRC). These lowlands show limited ecological niche and species diversity due to permanent soil moisture and various anthropogenic activities.

A total of 122 species, belonging to 83 genera, 37 families, and 23 orders, were recorded. These species fall into three cladistic categories: Eudicotyledons (77 species; 63.1%), Monocotyledons (44 species; 36.0%), and Pteridophytes (1 species; 0.8%). As in most savannah regions, pteridophytes are very rare throughout Aru Territory.

The floristic inventory was carried out in 10 phytocoenoses, including communities dominated by: Cyperus distans L.F. var. distans, Hyparrhenia subplumosa, Polygonum pulchrum Blume, Leersia hexandra Sw., Triumfetta cordifolia A. Rich var. cordifolia, Vossia cuspidata (Roxb.) Griff., Pennisetum purpureum K. Schum., Cyperus papyrus L. subsp. percamentus, and Ludwigia abyssinica A. Rich.

The Poaceae family is the most diverse (24 species), although the physiognomy of the vegetation is shaped mainly by Cyperaceae, dominated by Cyperus distans var. distans. The environment is favorable to geophytes and hemicryptophytes.

Anemochory is the predominant dispersal mode, with sclerochorous and sporochores being frequent. The phytogeographical spectrum is dominated by species with very wide distributions, with pantropical species being the most represented.

A perennial species of Melastomataceae, Centradenia inaequilateralis (Schltdl. & Cham.), was collected in the humid station as an indigenous species. Originally from Mexico, it is now introduced in tropical and subtropical regions, including Réunion Island, where it is cultivated in botanical gardens.

Floristic homogeneity was observed between some groupings, with a Sorensen coefficient of 60%, particularly between the mixed grouping (Triumfetta cordifolia var. cordifolia + Cyperus distans var. distans) and the Pennisetum purpureum community. Some phytocoenoses exhibited very low species diversity indexes and shared no species in common.

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