296 S. Afr. J. Bot. 1996.62(6): 296-305
Species richness and plant communities of the H elichrysum rugulosum-Hyparrhenia hirta Low-altitude grassland of northern K waZulu-Natal
H.C. Eckhardt: N. van Rooyen and G.J. Bredenkamp Department of Botany. University of Pretoria, Pretoria, 0002 Republic of South Africa
Received 20 Februor}' 1996: revised 30 July 1996
The condition of the grasslands of northern KwaZu l u~Natal is a source of great concern especially if seen against the background of a Jack of knowledge of the ecology of these grasslands. The aim of this study was therefore to produce a classifi cation and description of the plant communities of the Helichrysum rugulosum-Hyparrhenia hirta Low-altitude grassland, a major vegetation type of the area. The TWINSPAN classification and subsequent refinement there-of by Braun-Blanquet procedures resulted in the identification of 14 plant communities (vegetation units). The relationship of these communities to environmental factors was then determined by the application of the ordination algorithm DECORANA. Distribution of the synreleves was explained in terms of soil characteristics and degradation. The phytosociological data were further analyzed to determine the species richness of each community. This parameter, togeth er with species rarity and naturalness of communities, were collectively considered in an attempt to identify potential conservation sites. According to these criteria, one specific community was identified to be of conservational importance.
Keywords: Conservation sites, grassland, natu ralness, plant communities, species richness, vegetation units.
·To whom correspondence should be addressed.
Introduction JI1W 11".'- "W ;.::.------~------, n ~ .. 1' .. 'I1" .. r Deterioration of the grasslands of South Africa as a result of var MPUMALANGA ious factors is clearly realized (Mentis & Huntley 1982). Improvement in the quality of grassland management can only be achieved if based on detailed plant ecological studies (Codd 1949; Foran er al. 1986; Bosch er at. 1987). Existing vegetation descriptions and maps are often insufficient or have become obsolete. For the identification of conservation sites, it is impor tant to have as much detailed floristic data available as possible. Since little is known about the phytosociology and diversity of the grasslands of northern KwaZulu-Natal. this study aims at K W A A T .-'\ identifying and describing the plant communi ties of this area. Species richness, species rarity (Hall er al. 1980; Rapoport er al. 1986) and naturalness (Got mark 1992) were used as criteria on which the attempt to select conservation sites was based. The rN term 'naturalness' refers to the impact which man has had on the environment. During a study on the vegetation ecology of the grasslands of northern KwaZulu-Natal (Eckhardt er al. 1996a, b, c, d), the HelichrysulI1 rugu[osum- Hyparrhenia "irla Low-altitude grass land was identified as a major vegetation type. The plant commu :.,,,,", '-______+ _____--" : .J~ " nities. considered here as vegetation units, identified within this ,,~ maj or vegetation type are described and fl ori sti cally analyzed in this article. The flori stic and phytosociological analyses of the mG IlI.d)nd Sion.. northern KwaZulu-Natal region form part of a more comprehen • Siudy Ana sive study dealing with the syntaxonomy and synecology of the entire Grassland Biorne of South Africa (Bczuidenhout & Bredenkamp 1990; Kooij 1990; Du Preez 1991; Matthews 1991; Smit 1992; Bezuidenhout 1993; Burgoyne 1995; Coetzee 1993; T N Eckhardt 1993; Fuls 1993; Bredcnkamp & Bezuidenhout 1995).
Study area The entire study area (Figure I ) is situated in central-northern KwaZulu-Natal (Land Type Survey Staff 1986, 1988 ) and con sists of irregular undulating lowlands in the central and south western parts, undulating mountai ns and lowlands in the north western and eastern parts, and low mountains in the south-east ern part (Kruger 1983). The area is situated between 27°16' and Figure 1 Location of the study area within the Grassland Biome of 28°31'S latitude and 30°00' and 3 1°38'E longitude, comprising South Arrica. S. Afr. J. Bol. 1996,62(6) 297
14 366 km2• The high differences in altitudes within the area, unit, slope, soil depth, soil texture, clay content, rockiness of soil varying from 750 to 2290 m, can be asc ribed 10 the variety of surface and erosion. Although attention was also given to geology, physiographic regions and strongly affects the rainfall, the soil types and aspect, the results inferred that these factors did not annual average being 850 mm (Schulze 1982). The specific area affect the vegetation and are subsequently not referred to. covered by the Helichrysuni ruguLosum-Hyparrhenia hirra Low l\vo-way indicator species analysis (TWIN SPAN) (Hill 1979b) altitude grassland mainly includes the Hlobane-Manyini-C'eza was applied to derive the first approximation of the floristic data set Block, Bergville- Ladysmith-Elandslaagte Plain, Buffalo Plain, (see also Eckhardt el al. 1996a, b, c, d). The produced cl assificati on Dundee Plain, Ingagane Plain, Newcastle-Utrecht Plain, was further refined by Braun- Blanquet procedures (Westhoff & van Utrecht-Vryheid Plain and the Nondwcni-White UmfoIozi der Maarel 1978; Kooij ef af. 1990; Eckhardt ef al. 1993; Fuls ef nl. Basin (Turner 1967) (Figure 2). These lowlands are generally 1993a, b; Bredenkamp & Bezuidenhout 1995) to identify the differ ent plant communities, which were subsequently presented in a characterized by a relatively low average annual rainfall of 700 to phytosociotogical table. 800 mm and a relatively hi gh mean annual temperature of l7°C (Schulze 1982). This major grassland type highly corresponds The relationships between the vegetation and physical environ ment were identified using the ordination algorithm DECORANA with the Southern Tall Grass veld (65) and Natal Sour Sandveld (Hill 1979a). The synoptic data from the table, representing con (66) veld types of Acocks ( 1988) (Figure 3) and occurs primarily stancy values for species in the different vegetation units, were used at altitudes below I 400 m although certain communities may for the ordi nation (see also Eckhardt el ai. 1996b). occasionally be found at an altitude of up to I 800 m. Large areas The floristic data within each vegetati on unit were further ana falling within the Natal Sour Sandvcld (66) are pl oughed mainly lyzed to calculate a diversity (see al so Eckhardt et al. 1996a for a for maize production. These areas are primarily restricted to the marc detailed discussion). Buffalo and the Utrecht-Vryheid Plain (Figure 2). The nomenclatural type of each syntax on represe nts the typical Certain communities of this major vegetation type are also species composition of the relevant syntaxon, with special emphasis found on the Belelasberg-Skurwebcrg Plateau and the Helpme on the diagnostic species. The code of phytosociological nomencla kaar Plateau (Turner 1967) (Figure 2). ture follows that of Barkman el al. (1986). Methods Results and Discussion Relcves were compiled in 96 sample plots, which we re stratified on the basis of terrain units and aspect. Pial sizes were fixed at 100 m2 The Helichr)'sum ntgulosum-Hyparrhenia hirta Low-altitude (Scheepers 1975) and species recorded within the sample plots were grassland is predominantly restricted to midslopes of low-lying given a value according to the Braun- B1anquet cove r-aljundance « I 400 m) undulating plains and occurs sometimes on crests scale (Mueller-Dombois & Ellenberg 1974). Taxon names conform and fo otslopes (Figure 4). The slopes rarely exceed gradients of to those of Arnold & de Wet (1993) and the different plant communi 30, although some may reach ISO . Certain communities may lies were structurally classified according to the system of Edwards occur at altitudes reachi ng I 800 m, but Lhey are localized. Sur (1983). Environmental data recorded for each releve include terrain face rocks are rare but mostly absent in many of the communities
J O"OQ' 31"38' • B. I~ I •• bt"l.Skll,.....bt'1l Ph. lU ll , BiUI Dbtrg Rang.
8 Uclpln.kur Plat .. u '" Nqulu Di"i 2J N,,, (.as Ue-UI~ 10 20 ? , 30, 4p km JI) ' I~ " JI ·J~· Figure 2 Distribution of the physiographic regions within the study area (Turner 1967). 298 S. Arr. J. Bot. 1996.62(6) 11 ' 1 r ~ ~ r-;"rth"'U' lorn MDllnt,;n S"un.ld D I>S ~ ..I h.u TaU G .....,.ld o 66 :-'~1,1 ~Dur S~lKh.lcl o, 10 20 30 40, ~" Figure 3 The different veld types (Acocks 1988) found within the study area. and soits arc usually deeper than 500 mm and display clay per 1.2 Aristido bipartitae-Themedetu11l trial/drae hmchiarieto centages varying from 10% to more than 35%. sum scrratae (vegetation unit 2) The most common and physiognomically conspicuous species 1.3 Aristido bipartitae- Themedetlll1t triandrae Jelicietosllln throughout the grasslands of northern KwaZulu-Natal (Eckhardt I1wricatae (vegetati on unit 3) et al. 1996h. C , d) are the graminoids Eragrostis curvllla, E. 1.4 Arisrido biparrirae-Themedetul/l triw/(ime IllOIl.WllietoSflI11 plnna, HY]Jarrlienia hir/a and Sporobolus nfricatlllS (species wlglfstijoliae (vegetati on unit 4) group R, Table I). This major vegetation type shows clear signs 1.5 Aristido biparritae-Th emedetum triandrae eliOllffreto.mlll of disturbance, as indicated by species such as Heteropogon co/! mfllicfls (vegetation unit 5) tortus, Cymbopogoll excavaTUS and Aristidn jllllcijormis, as well 2. Sporoboletll.m pyramidafo- ajricani as those listed under group R (Edwards 1967: Tainton t 981 ; van 2. 1 Sporobolerlllll p),rm-nida/o-ajricatli eragrostielOsfllll Oudtshoorn 1991). sffperbae The average species richness fOf this major vegetation type is 2.1 .1 Brachiaria brizantha Variant (vegetation unit 6) 2 22 species per 100 m and the average total number of species 2.1.2 COIl)'za obscLtfa Variant (vegetation unit 7) recorded per plant community is 66 (Figure 5). Both these values 2.2Sporobolerum pyramidalo- a/ricml; berkheyeroswlI seti are low if compared to the fespective values of the Alepidea ferae (vegetation unit 8) longiJolia-Monocymbium ceresiiforme Grassland (28: 118) (Eck 2.3 Sporobo/etlln1 pyramidalo-ajricOIli pogOfltlrthrietoswll (II. Jftia hardt el I 996b). Panicum IIatalense- Emgroslis cllll sqllarrosae (vegetation unit 9) Grassland (24:68) (Eckhardt et 01. 1996c) and Helichr),slIIn 3. Aristido congesrae-Eragrostietwn g{lmmijlllae (vegetation pilosellum- Heteropogon contorlus Grassland (29:74) (Eckhardt unit 10) el al. 1996d) identified within the study area. It appears, there 4. Cenrello asiaticne- Eragrostietwn pInnae fore, that high-lying grasslands have a higher species richness 4.1 Centello asiaticae-EragrosrielW1t planae meliJ1ierosum than low-lying grasslands (see also White 1981. 1983; Matthews repens (vegetation unit 11) et 01. 1993; Eckhardt et 01. 1996b). 4.2 Centello asiaricae-Emgroslielul1l p/anae themedetosllm triandme (vegetation unit 12) Classification 5. Heteropogon cOlltortlls-Aristida junciformis Grassland (vege The analysis of the floristic data resulted in the identification of tation unit 13) 14 plant communities (Table 1) wh ich are subsequently hierar 6. Eragroslis plana-Sporobolus a/ricaJllls Grassland (vegetation chically classified (Barkman et 01. 1986). To facilitate the refer unit 14) ence to the different vegetation units, numbers are attached to each of the units. Description of the plant communi lies 1. Aristido bipartitae-Themedetum trialldme 1.1 Aristido bipartirae-Themedetwn triandme phyllantheto I. Aristido bipartitae-Themedetum rriandrae ass. nov. sl'lm burchellii (vegetation unit 1) Nomenclatural type: releve 77 (holotypus). '" OJ> ~ Hell chrysum rugulosum-Hyp.JrrflL'rna hJrta I ,.. Low- altitude grass land J !2'" :g 5>- '"N Midslopes , crests Midslopes at Midslopes at Midslopes and Mid s l opcs 2 and foots lopes at Midslopes at 800-1 200m < 1 ] OOm foots lopes at at >1 SOO m 1 000-1 800m <1 400m and at altitude altitude 1 200-1 8 00m altitude altitude 1 800m altitude - <1 5-25% clay -<15\ clay altitude -15- >35\ -mainly >35\ c l ay -15-» 51 - soi l depth -soil depth -15->35' c lay clay clay - soil depth 200->500mm >500mm -soil depth -soil depth 200- >500mm -soil depth -22 species >500mm <200->SOOmm >500mm per 1 00 m~ - 15 species -9 s pec ies I per lOamI per 100m~ Hidslopes Crests, mid Midslopes Midslopes Midslopes d.nd foot slopes and a t <1 300m Midslopes Midslopes Midslopes Mids lopes Midslopes at < 1 300m at <1 300m - <15-2 5% slopes at foots lopes a nd 1 BOOm altitude a l t i tude at <1 DOOm at ( I 15 0m at I 350m and foot <1 200m at <1 200m a ltitude c l ay a l titude altitude altitude slopes at -»5\ clay - >J5\ c l ay -soil depth altitude alti tude - 15-»5\ -soil depth -15 - 25' -15- 35% -15 - 25\ 1 200-1 800m -soil de pth 200-S00nun clay -10->35% - >35\ clay clay >500mm >500mm clay clay altitude clay -soil depth -soil depth -22 -28 species -soi l depth -so i l depth -soil depth ->35% clay species 2S0->500mm - soil depth >500mm 200->500mrn per lOamI per 100mz 300->500nun >SOOmm - soil depth JOO->SOOmm - 26 species - 27 species -25 s pecies -21 s pecies - 20 s pecies >SOOmro - 30 species per 100m2 per 1 00m2 per 100m' pe r 100m~ per 100m' -22 species per 100m 2 per 100m1 MidslopeIIs Midslopes at a t 800m 900-1 aOOm altitude altitude - lS-2Si -<151 clay clay - soil depth - soi l depth <200-S00rum 200-400mm - 23 s peci e s -19 species per 100rn~ per 100m2 1.1 1. 2 1.3 1.4 1.5 2. 1.1 2.1.2 2.2 2.3 3 4 . 1 4 . 2 , 6 Figure 4 Hierarchi cal cl assi fi cation and associated environmental characteristics of the 14 plaOl communities (vegetation units) of the Helic/u)'sum ruguLosum- Hyparrhenia hirta major vegeta N tion type. '" 300 S. Afr. J. Bot. 1996,62(6) Table 1 Phytosociological table of the Helichrysum rugulosum-Hyparrhenia hirta Low-altitude grassland Assocl at l o rl I 1 I? I Subanoci a tlon 11.1 I 1,2 1.3 I I ." 11.5 I 2 .1 I ?2 ;;> 1 1'1.11 '17 Var i a nt I I I I 2.1.12.1.2 I I Commun ' ty '>I , lhOLJt rank I I I ( r I I I I I ] I I 'j I 6 [ 10000 I 0000000 111 0 11111 [ 22012 102000 I 333 J 1153 13333333351333 33 1000000112222231 102130020011 U I U I 02212n~ 30 13 '1'/ 120~~2[ lie love number I 12 11 I 1111223581956679 I 05441 [ 365~8 1688 I 3 10 I 000222 350 11J51781 0035S59905S 772172012 30S391YIS9 1680982891911 114'1 1519 1 121751789303531[508901 169091 119059 1801 ( 724)23812613919;>;>88 13421798936 721'115115680865'185:> 14471] 779'1 1213710730 I Spec I as group A 1[1111 [111 1 1 1 1 , ,,. , , Arlit I da b I part I ta 11 A I .. lA 1 11 I , A' El l onurLls mutlcu$ 1 [I lA 11 lAl l I" , I" "IH I 1 B I " , , , H , Indlgcfera hadyantha I .. 1111 + 11 [ +1 11 I I , Geigeri. upar. 11 11 I [ + .. [ + 1 1 I , , Spec I as group B Led.bQur J. OVH!ro l la I .... " I 11+ "11 , , , , , , i , , PhyJ I.nthul burchllill [ 1 11"["1" I , , " " Hi biscus trlonum 1.... 1.. [ 11 I I~ 1 I + , , , , Cymbopogon plur l nodls I +1 I 1+1 11 , , , , " , , Antherlcln ruclcu l atum I lRI 1+1 + I , , , , , , I 1+[, 1+) , , , , , Oenothlrl tatrlptera • " Spec I or. group C , , , rellcla mllr lclta , , 11 1+"11111 , " Spec I os group 0 , IpomO"1 o",.,., I "IIyl I ...... +11++++1 I , , Cri bb .. I C8u li s I 11 +.. 11 1 1 1 1 ., " 8ra ehlllrl. s.rrata 111111+ I AA I " " " " Spec i as gr oup E Io(on$onl& ",gustlroll. I" 1+ 1 1 J 1 + 11++111 , , Strlga blleb l at. I R IR +' 1+ 1+1 +1+ + I , " Brachl.ril aruc l rormls I 1 I 11 1 [S 1 [ , Spec I as group f , , Set.r l ,sphlcelatl 181 A 1+ ,. ," " ,' , D I heteropogon amp l ecuns + + I .. , .,. .,, , Species group G Sporobo l us pyramidalis ISIJ3j"31 ) 331111R' I H,+4 11 " Spec I a s group H fr.gro~tls superb. [+11 11+11 80thI' I Dch I 08 1 nseu I pta IR"II " 11 Soec,es g~ouP I 8 rac hlarla br l Zlntl'la [R+l [ , Dlglta rla ternatl [ All , ~yporth8111 dlSlo l uta I 1AI " Spec I es group J , .... + 1+ I , , Sperm,eoee naUlansls , , , Blrkhayl lat lfar l , , , '", +11+ 11 11 , " 1" 1 Panun 111. I n!lUlt I fo I i I ., , 1+" 1" ., ., D I ehroltlchYI c I nera. , , ., , , " '" Specllu group K , Chlmlachrllt1 strlcta I +++ I ++ + .... + 1" 11 ., ConyZI ObSClif l 1++ 1 1 , l+ j ++R ", , , . , , ,, , Indlgohra vellltlni , + 1+ R+ '" '" " Spoc I e~ gr oup L Ar lstldl conga.ta ssp cengosta , , ., I" l 111 1Al 11 1 I , I(oh l utll v l r!llta , , 11 111++ 11+" I " PoroUs patens , , I 1 11 Al "B 11 , Stoebe vulgarll , , I .... R I , Spec I 05 group M Pogonarthr II aqutrrosa , , , , , 11 +) + 1 1A1+1+Bl [ [ , , ,. J.. 11 111 111+ 1 111 [1 Trlchoneurl gr.ndlglumls " " " SpllC I os group II , , , , Centell. asl l tlca , , [ 1 [++ 1 , , " 1"1 [ + 1 +1 11 , , , COfmle II nl! Ifr I Clnl ," , " • " I I + 1 11 11 , , flypocho~rls r.dlclt. '"", ,. '" " " " Spec I e s group 0 , l 11111Al1 1AA11+A l l )oI911n l i rep ens " 1+111+++111 " '" '" Soec I e s grouo P , 11 11 Arlstlda Congestl SSp barb i co i lis 1+11" 1 11+11111 ,. 11+1, 1 • ErlgroHls gurrrniflu. , " ., , , , ,,. 11 ""++ " 13AI1131" 1 311+ ")+1 1111 " ' , " 111"1" ...." l 11Al'"1 11 , , Cynodon dactyl on " , , , , , "M , , , , 'A A' , , , , "A T I + 11 , • +, "111 , + 1" .. J lorn II c a penll. , , , ,"" ,. " ,'" , , ." lIarmlnnl. tr,nlvulensis ,, , ., "• , , . , ++1"+ ", • " ,. , W,llfr I d. dans I f I Ort ". , , , " , , , ., '" " ,. '" • " , , " , , " , Ablld Erlgrost ls curvul. 11A38 11M3SMBB I ABAA3A13BI8B 11A 31 +1"ll1"1118BBI81111113AI A3M33B+3Al 3 [ 33A I 4~A 11 83313B \1 ABA 8+A] J 58+5414"31 Hyplrrhenll hlrtl 14331131 3+4AAB[34 ~331~lj53314SAA IA+A I433134333"~451334 5111411411348334433133111 11433A3 B 6 15B5ll4 +5411 8+ 1+R31 Er . grOltls pllnl IA1841 +AllAA411 1 1 11111 3AI +1" IT"'All + I" A I AlA + 1 1 1+131 +3M315B I II I 8" 31 ~5A~3 5AI Sporobalus arrlelnus I I 1 I \ 1 11 1 AI+1 11 lIAAll1Al++1 1+1 11 .. Al11BI + 11 .. +1 I 11 1 l iA1B J\6BI S. Afr. J. Bot. 1996,62(6) 301 Average species richness This short to tail closed grassland is mainly found on mid slopes « 3°) in the undulating plains landscape at altitudes 30 below I 400 m (Figure 4). This grassland can also, to a lesser. degree though, be found on crests and footslopes and sometimes 25 ~E at altitudes of up to 1 800 m. The major physiographical r.egions " to which this grassland is restricted are the Buffalo Plain, Dundee "3 -70 Plain, Ingagane Plain, Newcastle-Utrecht Plain and the Utrecht ~ Vryheid Plain (Turner 1967) (Figur.e 2). Soils ar.e relatively rich IS 25 in clay (> 35%) and deeper than 500 mm. Isolated occurrences of ] 10 surface rocks may be obscrved, hardly covering 5% of the sur ':3 face. The diagnostic species are included in species group A 9- 5 (Table 1). Aristida bipartita is associated with clayey, often ver a tic, soils (van Oudtshoorn 1991). The most dominant species are i 2 3 4 5 6 7 8 9 to I I 12 13 14 Themeda triandra, Eragrostis curvet/a and Hyparrhenia hirta Vegetation units (Table 1). Five sub-associations are recognized under this association: Total species per. vegetation unit 1.1 Aristido bipartitae-Themedetum triandrae phyllantheto sum burchellii sub-ass. nov. 120 Nomenclatur.al type: r.eleve 77 (holotypus). § c 100 This grassland occurs on midslopes and foots lopes at altitudes 2 ;; below I 200m (Figur.e 4). Clay content of the soils varies fr.om :; 80 10% to mor.e than 35% and Ihe depth fr.om 300 to mor.e than 500 '""> - - mm. No surface rocks were recorded. 60 =- This sub-association contains no diagnostic species, but is dis ":3""" 40 tinguished by the presence of specics groups A, Band E and the ~" - absence of species groups C, D and F (Table 1). Most prominent ;; 20 species include the grasses Hyparrhenia hirta, Eragrostis cur c villa and E. plana (Table 1). This is the typical sub-association of "'5 0 z 2 3 4 5 6 7 8 9 10 11 12 13 14 the Aristido bipartitae-Themedetum triandrae association. Vegetation units This community has the highest average species richness (30) Figure 5 The average species richness and total number of spe recorded for a community in this major vegetation type, and a cies for each vegetation unit. Horizontal lines indicate the averages total number of 63 species (Figure 5). In contrast to this commu for the HeIiclll}'sum rugulosum- Hyparrhenia hirta major vegetation nity, the Aristida bipartita-Themeda triandra Grassland occur type. ring apparently under similar environmental conditions and '" , N• " , ~ " ' " £I. " " '" '" , .. Axis 1 Soils Soils Clayey A~------.p,b Sandy Dry q~---- Moist -----17b Dry Undisturbed Disturbed Figure 6 The distribution of the synreleves (14 plant communities) along the first, second and third axes of a DECORANA ordination (Eigen values: axis I = 0.39, axis 2 = 0.167, axis 3 = 0.081). 302 s. Mr. 1. Bot. t 996,62(6) described by Fuls et al. (I993a), has only an average of 23 spe and the depth usually exceeds 500 mm. Surface rocks arc mostly cies per sample plot. absent. Diagnostic species are absent from this sub-association, which 1.2 Aris/ida bipartitae- Themedetum trialldrae brachiarieto is distinguished by the absence of species groups B to E, and the sum serra/ae sub-ass. nov. presence of species groups A and F (Table I). Physiognomically Nomenclatural type: releve 20 (holotypus). conspicuous and dominant species are Themeda triandm and This grassland occurs on crests, mid slopes and foots lopes at Hyparrhenia izirta (Table I). altitudes below I 200 m (Figure 4). In general, the soils are This grassland community has the second highest average spe clayey (> 35%) and deep (> 500 mm), with surface rocks some cies richness (28) of all communities within this major vegeta times present, then covering up to 5% of the area. tion type. with the total number of species being 78 (Figure 5). Ahhough no diagnostic species were identified, this grassland community is distinguished by the simultaneous presence of spe 2. Sporoboletum pyramidata-africani ass. nov. cies groups A, B, D, E and F (Table I). Well-preserved areas Nomenclatural type: releve 303 (holotypus). within this grassland are recognized by [he presence of the grass This short to tall grassland of midslopes « 3°) is primarily Brachiaria serrata (species group D, Table 1). Other prominent restricted to altitudes varying from 800 to 1 200 m (Figure 4). species are Themeda (riam/ra, Hyparrhenia hirta. Eragrostis The major physiographical regions with which this grassland is cllrvula and E. plana (Table 1). The strong presence of Themeda associated arc the Hlobanc-Manyini-C'eza Block and the Nond triandra is a clear indication of the relatively good condition of weni-White Umfolozi Basin (Turner 1967) (Figure 2). Soi ls are this community (Gibbs Russell ef al. 1991; van Oudtshoom relatively sandy. varying in clay contents from less than 15% to 1991). 25%, and the depths varying from 200 to more than 500 mm. The average number of species recorded per sample plot is 26. Surface rocks are virtually absent throughout this grassland. with the total number of species for this community being 93, The only diagnostic species is the tough unpalatable grass which is well above the average for the major vegetation type Sporobolus pyramidalis (species group G. Table 1) which is an (Figure 5). indicator of overgrazed and trampled veld (Gibbs Russell et (It. 1991: van Oudtshoom 1991). Other prominent species include 1.3 Aristido bipartitae-Themedetllln triandrae felicierosum Cymbopogoll excavalUS. Eragrostis curvula and Hyparrhellia muricatae sub-ass. nov. hirta (Table 1). Noteworthy are the low cover-abundance val ues Nomenclatural type: releve 170 (holotypus). and only the occasional occurrence of Themeda triandra. empha This sub-association is mainly associated with midslopes at sizing the relatively poor condition of this grassland association. altitudes below I 300 m, although isolated patches are also found at an altitude of up to I 800 m (Figure 4). Clay content of the 2.1 Sporoboletum pyramidalo-africani eragrostietoJwn soils varies from 15% to more than 35% and depth from 200 to superbae sub-ass. nov. more than 500 mm. Surface rocks are present. but usually cover Nomenclatural type: rei eVe 381 (holotypus). less than 2% of the area. This grassland is found on mid slopes. with soils being rela The only diagnostic species is the small shrub Felicia muri tively sandy « 15-25% clay) and the depth varyi ng from 200 to cata (species group C, Table I), an indicator of overgrazing (van 500 mm (Figure 4). Isolated occurrences of surface rocks may be Wyk ef al. 1988). Species groups A, D and E (Table I) are also encountered, covering less than 2% of the area. present. Physiognomically. the most conspicuous and dominant The diagnostic species arc the grasses Eragrostis superba and species are Heteropogon con/ortus, Themeda (riandra, Eragros Bothriochloa illsculpta (species group H, Table 1). bQ[h species tis curvula and Hyparrhenia hina. with the absence of Eragrostis being indicative of disturbed veld (Gibbs Russell ef al. 1991; van plana suggesting relatively dry conditions (Gibbs Russell ef al. Oudtshoorn 1991). The most dominant species are Sporoholus 1991; van Oudtshoorn 1991) (Table I). pyramidalis and Hyparrhellia hirfa (Table I). This community has an average species richness of 27 and a total number of 70 species (Figure 5). 2.U Brachiaria brizanfha Variant This variant occurs on midslopes at an altitude of 800 m (Figure 1.4 Aristido bipartitae-Themedetum triandrae monsanieto 4). Clay content of the soi ls varies from 15 % to 25% and the sum angusllfoliae sub-ass. nov. depth from 200 to 400 mm. Widely scattered surface rocks may Nomenclatural type: releve 206 (holotypus). occur. usually covering less than 2% of the area. Since the basal This community is found at altitudes below I 300 m and grass cover is relatively low. signs of erosion could be clearly occurs primarily on midslopes (Figure 4). The soils are clayey detected. (> 35%), the depth of which usually exceeds 500 mm. Surface This grassland is characterized by the diagnostic grass species rocks are generally absent. listed under group I (Table I), however, the dominant species are No diagnostic species were recorded. although this commu Sporobolus pyramidalis and Hypal'rhellia hirta (Table 1). nity can be distinguished from the previously described sub The average number of species recorded per sample plot is 19. associations by the absence of species groups B. C and D, and wit h the total number being 33. which is the lowest to be the presence of species groups E and F (Table I). Prominent spe recorded within this major vegetation type (Figure 5). cies are Eragrostis curvula and Hyparrhenia hirta (Table I). The average number of species recorded per sample plot is 22. 2.1.2 Conyza obscura Variant with the total number of species being 51 (Figure 5). This variant is found on midslopes at altitudes ranging from 900 to I 000 m (Figure 4). Soi l depth varies from less than 200 to 500 1.5 Aristido bipartitae- Themedetum triandrae elionuretostlm mm and the clay content is less than 15%. Surface rocks arc muticus sub-ass. nov. scarce and widely scattered. covering less than 2% of the area. Nomenclatural type: releve 50 (holotypus). Although this grassland is not characterized by diagnostic spe This grassland occurs mainly on midslopes at altitudes below cies, it can be distinguished from the Brachiaria brizantha Vari I 300m (Figure 4). The clay content of the soils exceeds 35% ant by the absence of species group I and the presence of species S. Afr. J. Bot. 1996.62(6) 303 group K (Table I). Physiognomically, the most conspicuous and This short to tall grassland is restricted to moist conditions dominant species are usually Sporobolus pyramidalis and Hypar which occur on midslopes and footslopes at altitudes ranging rhenin hirta (Table 1). from 1 200 to 1 800 m (Figure 4). The primary physiographical The species richness (23) is slightly higher than the average regions with which thi s grassland is associated are the Belelas species richne ss for the major vegetation type, however the lotal berg- Skurweberg Plateau, Buffalo Plain, Dundee Plain, New number of species is only 35 (Figure 5). castle-Utrecht Plain and the Utrecht-Vryheid Plain (Turner 1967) (Figure 2). Soil depth generally exceeds 500 mm, wirh the 2.2 Spombo[etum pyramidalo-africani berkheyetosul1l seti clay content varying from J5% to more than 35%. No surface ferae sub-ass. nov. rocks are present. Nomenclatural type: re1eve 303 (holotypus). This association is characterized by the diagnostic but incon This grassland occurs primarily on midslopes al ahitudes spicuous forbs listed under species group N (Table I). The pres below I 000 m (Figure 4). Clay content of the soils varies from ence of these species as well as th e prominence of Eragrostis 15% to 25% and the depth from 250 to more than 500 mm. Sur plana clearly indicate moist soil conditions. The most dominant face rocks arc mostly absent from this grassland. species are Eragrostis curvu[a, E. plana and Hyparrhenia hirta The diagnostic species which characterize this community (Table I). include the forbs listed under species group J and the sparsely scattered shrub Dic:hrostachys cinerea (Table 1). The most prom 4.1 Centello asiaticae- Eragrostietum planae melinietosum inent species are Sporobolus pyramidalis. Eragrostis cun'llia and repens sub-ass. nov. Hyparrhenia hirta, with Cymbopogoll exclIvafus and Sporobolus Nomenclatural type: releve 25 (holotypus). lIjric(lllus being less prominent (Table 1). This is the typical sub This grassland occurs on moist midslopes at an altitude of association of the association. I 350 m (Figure 4). Soils are deep (> 500 mm) and display a clay A re latively high ave ragt:! specit:!s richness of 25 was recorded, content of 15% La 25%. Surface rocks are absent from this corn· with the total number (90) also very high (Figure 5). munity. The only differential species which distinguishes this grass 2.3 SporoboletIlln pyramidalo-ajricalli pogonarthrietosum land is the grass Melillis repells (species group 0, Table 1), squarrosae sub-ass. nov. which is indicarive of disturbed veld (van Oudtshoorn 1991). The Nomenclatural type: releve 388 (holotypus). most prominent species include Heleropogon contortus, Era This grassland is found on mid slopes at altitudes below I 150 grostis cunluia and Hyparrhenia hirta, with Themeda triandra m (Figure 4). The clay content of the soils varies largely from being absent from this community (Table I). 15 % to 35% and the depth from 300 to more than 500 mm. Sur The average number of species recorded per sample plot is 20 face rocks are absent throughout this grassland. and the total number is 46 (Figure 5). No diagnostic species were identified for this community, however, the latter can be distinguished by the absence of species 4.2 Centello asiaticae-Eragrostietum planae th emedetoswn groups H, I and J, and the presence of species group K and the triandrae sub-ass. nov. differential species Pogonarthria sqllarrosa and Trichoneura Nomenclatural type: releve 38 (holotypus). gmndiglwnis (species group M, Table I). Conspicuous and often This grassland is primarily found on moist midslopes and foot dominant species include Sporobolus pyramidalis, Heteropogon slopes at altitudes varying from I 200 to I 800 m (Figure 4). contortlls, Eragrostis cun1uta and Hyparrhenia hirfa (Table 1). Although the clay coment of the soil s varies considerably, in The average number of species recorded per sample plot is 21 most cases a percentage of more than 35% was recorded. Soil and the total number 57 (Figure 5). depth usually exceeds 500 mm, with surface rocks being absent from this grassland. 3. Aristido congestae-Eragrostietum gummifluae ass. nov. Although no diagnostic species were recorded, this commu Nomenclatural type: releve 199 (holotypus). nity is nevertheless distinguished from the CenteJlo asiaticae This short to tall grassland is encountered on midslopes at alti Eragrostietum planae melinietosum repe1ls by the absence of tudes below I 300 m (Figure 4). This grassland is primarily asso species group 0 (Table I). Despite the presence of Themeda tri ciated with the Bergville-Ladysmith-Elandslaagte Plain, Buffalo andra, this grassland is in a relatively poor condition, with areas Plain, Dundee Plain, Newcastle-Utrecht Plain and the Utrecht subjected to heavy selective grazing and dominated by Aristida Vryheid Plain (Turner 1967) (Figure 2). The soils display a pre JWlciformis (Table I). The most prominent species are Eragrostis dominantly sandy texture, containing less than 15% clay and are cllrvu/a, E. plana and Hyparrhenia hirw (Table 1). This is the usually deeper than 500 mOl. No surface rocks we re found typical sub-association of the association. throughout this grassland. Despite a low average species ri chness of 22, a high total The diagnostic species are included in species group L (Table number (105) of species was recorded for this communi ty (Fig 1). These grasses and the dwarf shrub Stoebe vulgaris are typical ure 5). This number exceeds the total number of all other com indicators of disturbed veld (van Wyk et 01. 1988; Gibbs Russell munities of this major vegetation type by far. et 01. 1991; van Oudtshoorn 1991). Perotis patens and Ihe con spicuous Eragrostis gummij1ua (species group p, Table 1) are 5. Heteropogon contorltts-Aristidajunciformis Grassland also indicative for leached sa.ndy soils. Other prominent species This short to tall grassland occurs mainly on midslopes at alti include Melinis repens, Heteropogoll confortus, Eragrostis cur tudes exceeding I 500 m (Figure 4). It is generally restricted to vu/a and Hyparrhellia hirta, with Themeda triandra being com the Belelasberg-Skurweberg Plateau and the Helpmekaar Pla pletely absent (Table I). teau (Turner 1967) (Figure 2). The clay content of the soils varies An average species richness of 22 was recorded, whereas the considerably from 15% to more than 35%, whereas soil depth total number of species is 83 (Figure 5). varies from less than 200 to more than 500 mm. Surface rocks are occasionally found, then covering up to 20% of the area. 4. Centello asiaticae-Eragrostietum planae ass. nov. No diagnostic species were identified, with the community Nomenclatural type: releve 38 (holotypus). being distinguished by the presence of species groups Q and R 304 s. Afr.1. Bot. 1996, 62(6) (Table 1). Most prominent species include Eragrostis cllrvula of undisturbed areas of Natal Sour Sand veld occurring outside and Hyparrheflia hirta, with Heteropogon COlltortus and Aristida the study area, this will be estimated once the syntaxonomy of jUllciformis being sometimes dominant where selective over the KwaZulu-Natal grasslands has being completed. The Aristido grazing has been prevalent or where soils are shallow and rocky bipartitae-Themedelllm rriatldrae phyllaflthetosum burchellii is (Table I). the community with the highest species richness (30) within this This community has an extremely low average species rich major vegetation type. Although this figure is not particularly ness of 15, wilh Ihe lOIal number of species being 71 (Figure 5). high, it exceeds the species richness of many hitherto described grassland communities occurring in other parts of the grassland 6. Eragroslis plana-Sporoboills african"s Grassland biome (Kooij er 01. 1990; Fuls er 01. 1993a, b; MaUhews el al. 1994). However, species richness should not be used on its own This short to tall grassland is not strictly associated with certain as a criterion when determining conservation priorities, because environmental conditions, occurring throughout the study area it gives no indication of the number of endemic or rare species mainly on mid slopes at aHiludes ranging From 1 000 10 I 800 m (Pomeroy 1993). Instead, the prioritization of conservation sites (Figure 4). II is also not reslricled 10 any specifi c physiographical could be improved by taking account of several different factors. region (Turner 1967) (Figure 2). Clay percenlages vary From No rare species were identified in any of the described communi l5% to more than 35% and soil depth exceeds 500 mm. No sur lies (Hall el al. 1980). Another specific area which also needs 10 face rocks were encountered. be seriously considered for conservation is the Blood River vIei, This community is not characterized by diagnostic species and situated between the Skurweberge and Bloedrivier station. This consists primarily of the prominent species Eragrostis curvu[a, vIei belongs to the Aristido bipartitae- Themedetum triandrae E. plana, Hyparrhenia hirla and Sporobolus africanus (Table I). brachiarietosum serratae and is dominated by dense stands of It is distinguished from the Heteropogon cOlllorlus-Aristida jun· HyparrheIJia hirla. Although this vlei is currently heavily uti ciformis Grassland by Ihe absence of species group Q (Table I). lized, it should be seriously considered for preservation because The high cover-abundance values of the strong competitors Era· of the importam ecological role which it fulfils, serving amongst grostis plaIJa and Sporobolus africanus are clear indicators of olhers as a sponge area for the Blood River. The identified and disturbed and overgrazed veld in high·rainfall regions (Tainton des·cribed communities could assist farmers in the compilation 1981; van Oudlshoorn 1991). Under COnlinuous heavy grazing of management plans and in their decision of which areas are to pressure, these species will gradually replace more palatable spe· be preserved (see also Wahl 1995). cies, resulting in the decline of the grazing capacity of this grass land. Acknowledgement The species poorness of this community is clearly reflected by This research was financially supported by the Department of the average species richness (9) and lolal number (47) of species Environmental Affairs and Tourism. (Figure 5). References Ordination ACOCKS. J.P.H. 1988. Veld types of South Africa, 3rd cdn. Mem. hot. A three· dimensional scatter diagram is presented in Figure 6, S1Irv. S. AI, 57: 1-1 46 . displaying the distribution of synreleves along the first, second ARNOLD, T.H. & DE WET. B.C. 1993. Plants of southern Africa: and Ihird axes of a DECORANA ordination. AH hough Ihey have names and distribution. Mem. bot. Sit"'. S. AJr. 62: 1-825. no clear distinct discontinuous groups, the three vaguely defined BARKMAN, J.J .. MORAVEC. l. & RAUSCHERT, S. 1986. Code of groups could be explained in terms of certain environmental fac phytosociological nomenclature. 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