The Hydrophilic Vegetation of the Vredefort – Kroonstad – Lindley
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S.Afr.J.Bot., 1992,58(4): 231 - 235 231 The hydrophilic vegetation of the Vredefort - Kroonstad - Lindley - Heilbron area, northern Orange Free State E.R. Fuls, G.J. Bredenkamp and N. van Rooyen Department of Botany, University of Pretoria, Pretoria, 0002 Republic of South Africa Received 23 October 1991; revised 31 March 1992 An analysis of the plant communities of the watercourses of the Vredefort - Kroonstad - Lindley - Heilbron area (northern Orange Free State) is presented. Releves were compiled in 34 stratified random sample plots. A TWINSPAN classification, refined by Braun-Blanquet procedures, revealed four distinct plant communities. A hierarchical classification, description and ecological interpretation of the plant communities are presented. 'n Analise van die plantgemeenskappe van die waterbane van die Vredefort - Kroonstad - Lindley - Heilbron area (noordelike Oranje-Vrystaat) word gegee. Releves is in 34 gestratifiseerde ewekansig gekose monsterpersele saamgestel. 'n TWINSPAN-klassifikasie, verfyn deur Braun-Blanquet-prosedures, toon vier duidelik onderskeibare plantgemeenskappe. 'n Hierargiese klassifikasie, beskrywing en ekologiese interpretasie van hierdie plantgemeenskappeword aangebied. Keywords: Braun-Blanquet classification, grassland biome, synecology, TWINSPAN Introduction Kroonstad map (1:250 (00) (Land Type Survey Staff 1984), The northern part of the Orange Free State is one of the within the climatic climax grassland biome of southern most important agricultural regions of southern Africa, both Africa (Mentis & Huntley 1982). The area is situated in terms of intensive crop production and extensive stock between 27°11' and 28°lO'E longitude and 2rOO' and farming (Scheepers 1975; Mentis & Huntley 1982). The 28°00'S latitude (Figure 1). Towns situated in, or widespread ploughing of arable land concomitant with bordering on, the study area are Kroonstad, Heilbron, livestock grazing pressure resulted in the destruction of large portions of pristine vegetation in the area. The sensitivity of hydrophilic vegetation makes the watercourses especially vulnerable to degradation. Increased run-off and 27', 27~30'E 28"E 270$ -+-------='"77777777:7'7":''777777:7"!""'-'---,-27'S erosion, liberal use of fertilizer and pesticides within catchment areas, as well as indiscriminate utilization by livestock, are but a few aspects which contribute to water course degradation in the area. Since the broad vegetation classification and mapping presented by Acocks in 1953 (Acocks 1953, 1988), very little advance has been made towards a more detailed classi fication and description of the vegetation of the area. In 27'l30'S 2]030'$ view of the predicament of the natural vegetation of the study area, it is imperative that future land-use planning, management and conservation strategies are based on sound plant ecological principles. To facilitate optimal resource utilization in general, and to assess the conservation status of the vegetation in particular, a detailed identification, classification and mapping of the vegetation of the region 28CS has been undertaken. The physical environment and major 27', vegetation types, the plant communities of the rocky out crops and the undulating grasslands of the study area are 21" described by Fuls et al. (1992a), Fuls et al. (1992b) and Fuls et al. (l992c), respectively. In this paper the plant commun ities and associated habitats of the watercourses of the 25' northern Orange Free State are described. This study forms f an integral part of the ultimate goal to compile a compre 29' N hensive syntaxonomical synthesis of the grasslands of south ern Africa (see also Bredenkamp at. 1989; Kooij al. Cape Provin ce o ~OO "m et et "'===='=====' 33°5 1990). 33'S 19' Study area Figure 1 The study area (hatched) in which the hydrophylic The study area comprises the eastern pan of the 2726 vegetation of the watercourses was analysed. 232 S.-Afr.Tydskr.Plantk.,1992,58(4) Vredefort, Lindley and Koppies. The area covers approxi Taxa names conform to those of Gibbs Russell et al. (1985, mately 750000 ha. The study area forms part of the High 1987). veld inland plateau, consists predominantly of smoothly Two-way indicator species analysis (TWINSPAN) (Hill plained or gently undulating land surfaces of the Miocene 1979) was applied to the floristic data set in order to derive age (Mentis & Huntley 1982) and is situated between 1300 a first approximation of the vegetation types of the area. m and 1700 m above sea-level. The topography comprises a Refinement of this classification was done by means of mosaic of flat, slightly undulating and undulating terrain Braun-Blanquet procedures (Bredenkamp et al. 1989; Kooij (Land Type Survey Staff 1984). Isolated hills and ridges are et al. 1990). encountered occasionally. The area covered by the water Results courses comprises less than 5% of the study area (Fuls et al. 1992a). The watercourses are not particularly species-rich, being Drainage of the study area is variable with the major mostly dominated by a few herb species (Table 1). A total portion thereof reasonably well-drained to well-drained. of 123 species was recorded in the 34 sample plots, with the Permanently waterlogged soils, pans and vIcis are scarce average number of species per sample plot being 21. From the final differential table, four plant communities and seasonally standing water is mostly restricted to slow were identified (Table 1). draining watercourses. Slow-draining streams are common A diagrammatic presentation of the hierarchical classifi owing to the flatness of the terrain in most parts of the study cation and associated environmental interpretation of the area. The major rivers draining the area are the Va Is River four plant communities is presented in Figure 2. and Renoster River. The main drainage is from the higher lying south-east towards the lower lying north-west. The Description of the plant communities study area forms part of the catchment area of the Vaal The floristics and associated environmental attributes for the River below the Vaal Dam. Stream incision is mostly respective plant communities (Table 1) are given below. shallow except for the Vals and Renoster Rivers and a few of their main tributaries. 1. Andropogon appendiculatus - Cyperus jastigiatus Wetland (type releve: 79) Methods The vegetation of the watercourses can be broadly classified Releves were compiled in 34 stratified random sample plots. as an Andropogon appendiculatus - Cyperus Jastigiatus Stratification was based on depth of streambed incision, Wetland (Table 1). Graminoids with a high constancy in this topography, drainage variation and land type [Bd Land Type community include Eragrostis plana, Paspalum dilatatum, / Dc Land Type (Land Type Survey Staff 1984)] . Plot sizes Cynodon dactylon, Pennisetum sphacelatum and Setaria were fixed at 100 m2 (Scheepers 1975). In each sample plot nigrirostris (species group H - Table 1). Forb species which all species were recorded, using the Braun-Blanquet cover are commonly encountered include Berkheya radula, Haplo abundance values (Mueller-Dombois & Ellenberg 1974). carpha scaposa, Cyperus longus and Mariscus congestus Watercourses l - Deep/intermediate - Shallow streambed streambed incision incision - Fast drainage - Slow drainage - Stagnant water - Stagnant water mostly absent often present - Streambanks dry - Stream banks moist - Overutilized/ disturbed - Intermediate streambed incision - Deep streambed - Intermediate incision streambed - Streambanks incision relatively dry - Streambanks - Fast run-off relative (periodic moist flash-floods) ,. '" 1.1.1 (a) 1.1.1 (b) 1.1.2 1.2 Figure 2 The hierarchical classification and associated environmental characteristics of the four plant communities. Numbers of plant communities correspond with descriptions in text. 233 S.AfrJ.Bot.. 1992. 58(4) Table 1 Phytosociological table of the hydrophilic vegetation of the northern Orange Free State Corrmun i ty numbe r 1.1 1.2 1. 1. 1 1. 1. 2 A B 111101111 1111100 000011000 100100010 Re I eve numbe r 847882243 6500395 217715468 004482617 176351641 5309731 099379894 665138130 Species Group A Rhus pyroides IRRRRR+ R+I I I I Acacia karroo IR+RRR+R 11 R 1+ R + I I Prot asparagus laricinus 1+++R11 11 I RR I+RR I I Cyperus marginacus IBBBB+ A 1+ I 3 1 + I Al I Verbena bonariensis I R++ RRI RRI R I R I Cymbopogon excavatus IR++ R I R I I I Vigna vexillata IRR RR I I I I Asclepias rrucicosa IR R RR IR IR I I Crotalaria virgulaca I R+ R I I I I Bromus catharticus I RR+ I I I I Hyparrhenia hirta IAA+ IA I + I I Ranunculus multifidus I + R +1 + I R IR I Gomphostigma virga tum IR+ + I + I + I I EquiseCum ramosissimum 11 I I + I I Rumex lanceolatus I + R I I R I I Juncus exsertus 1+ A I I I 1 Spec ies Group B Pulicaria scabra R I+R R R I Fuirena coerulescens I 1 1 + R I Phragmites australis R 1+1 +1 Species Group C Aster squamatus 1++ +R RRRIRR RRR I + I I Lobelia thermalis IRR R ++11+++RR I I I Trirol ium pratense I RR R +I+R+RR RI IR RRI Agrostis lachnantha IR +1 R RIA++ +1 ++ + I 1 1 I Berti I a erec t a IR + R 11A I + I I Spec ies Group 0 Oenothera rosea I R++ +IR IRRRRR R I Conyza bonariensis 1+ I R IRRRR R I + Echinoehloa haploclada I B 3 R I 13A R R IR+ Secaria pal I ide-rusea I + I R I Bl R RI R Verbena orricinalis I + I 1++ RR I Spec ies Group E + lBI Hemarthria alcissima IA+ A+AAA3IB3ABAAAIABB1A+B3BI Cymbopogon plurinodis I RAR +A I ++RR R I R AR+R I R I Gal ium capense IR + 1+ IRR RRI++ + RRI RI Rumex crispus IR R RRR I + RI R R I I Typha eapensis I RR