Boomplantweek en die Internasionale Jaar van Woude - Dendro.co.za

DENDRON » No/Nr: 43 » November 2011
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NEW TREE SPECIES DISCOVERED IN KWAZULU-NATAL
New tree species discovered in KwaZulu-Natal!
A newly discovered tree species found only in
KwaZulu-Natal was recently published in the South
African Journal of Botany. The tree is a species of
Combretum, popularly known as bushwillows, many
of which are common and conspicuous features of
the African bushveld.
The new tree has been named Combretum stylesii,
and is a rare species known so far only from a
rugged, ten kilometre stretch of the Tugela River,
within the Maphumulo District Municipality to the
north of Durban. It appears to have been hidden by
its inaccessible habitat, although this is now being
threatened by road development and rural sprawl.
The tree is named after David Styles, a member
of BotSoc KZN Coastal Branch who has collected
several thousand plant specimens in the province
over the past decade, in the process discovering
a number of other, smaller plant species. David is
editor of the journal published jointly by BotSoc KZN
Coastal Branch and the Durban Botanic Gardens
Trust, PlantLife, and he is founder and administrator
of the Yahoo! discussion group, Plant-chat.
David first found the tree in 2004, but although he
realized that it was an unknown species, both fruits
and flowers were needed in order to complete its
description. It took four years for this to occur. As
David explains: “the locality is remote and flowering
is brief and erratic. Many visits were made to the
area. In some years no flowers were found or
flowering was just missed.”
Eventually complete material was collected and
sent to Olivier Maurin, a Ph.D. student studying
the family at the University of Johannesburg, and
Professor A.E. (Braam) van Wyk, the renowned plant
taxonomist based at the University of Pretoria.
In addition to more obvious distinguishing features,
bushwillow species can be distinguished from each
other by tiny scales on the leaves that are as unique
as a human fingerprint. The scales of Combretum
stylesii were also studied under a microscope and
Marilyn Bodasing
LEAVES & FRUIT of the » Combretum stylesii
its DNA was analyzed, proving its distinctness from
other known species.
The tree grows both on its own and as a vigorous
strangler, climbing up and over other trees. The
vegetation in which it occurs is classified as Eastern
Valley Bushveld and the area is arid and hot with
temperatures often reaching over 40 degrees
centigrade in the summer.
According to David, “It is possible that this new
Combretum occurs at other localities in this area, as
vegetation along this part of the Tugela River is not
well known.” He also believes that more exploration
of this interesting area could result in other new
discoveries being made.
Combretum stylesii grows easily from seed, and is
currently being grown at the Kirstenbosch National
Botanical Garden.
Author:
Marilyn Bodasing, University of KwaZulu-Natal
Photo credits:
David Styles
This article was previously published in the September 2011
issue of the Veld & Flora.
Published in the Dendron with kind permission of the authors.
Die grootste gedeelte van die noordoostelike
Springbokvlakte (Limpopo) word onderlê
deur ‘n substraat van basaltiese lawa en sekondêre
wit kalksteen. Van horison tot horison is dié
wêreld plat. Vorentoe en agtertoe lyk albei ewe
opdraand! Die algehele afwesigheid van panne
en duidelik gedefinieerde waterlope val ‘n mens
dadelik op. Die waterlope bestaan in werklikheid
uit breë, vlak laagtes wat moeilik met die blote oog
waarneembaar is en slegs na groot reëns loop. Die
enigste afwisseling in die gelyk landskap is ‘n breë
strook sand wat die noordelike Vlakte van die suide
skei, die sogenaamde sandbulte.
Die basalt skep ‘n uitgestrekte, struikagtige,
doringboom-oorheersde bosveld op die
kenmerkende basaltiese kleigronde. Groot
gedeeltes is egter al ontbos en vir akkerbou
aangewend of deur ander menslike aktiwiteite
getransformeer. Die geoloog, Wagner (1927) het dit
treffend beskryf: “The flats proper are characterized
by their level nature --- the almost entire lack of well
drained water-courses and their peculiar black and
red soils. They are made up of great expanses of
apparently level grassland and tree steppe --- The
grassland marks the position of the area occupied
by black turf soil. It is normally devoid of trees, but
supports an abundant growth of dwarf bush-like
acacias.”
Die swart turf is ‘n vrugbare, swaar, swakgedreineerde
kleigrond wat in situ ontwikkel het.
Volgens Wagner (1927) is dit ‘n fosfaatryke grond
met sterk rek- en krimpeienskappe: “The black
turf is a heavy residual clay soil of greyish-black
or bluish-black colour, rich in colloids. It swells
very considerably when wetted and on drying
develops gaping shrinkage cracks which divide
into polygonal (veelhoekige) columns. Its marked
fertility is due mainly to the high ratio of available
to total phosphorus. The black turf forms a layer
from 1 to 8 feet in thickness, generally underlain
by nodular calcareous tufa.” Die “colloids” waarna
die outeur verwys staan in Afrikaans bekend as
kolloïdale deeltjies; dit is kleiminerale of organiese
deeltjies met ‘n deursnee van 0.0005 tot 0.000001
mm wat nie in water oplos nie, maar klein genoeg is
om daarin rond te dryf.
Só ‘n plek is Malgas (154 KS, 2429 AC Zebediela-
Wes), suid van Immerpan – ‘n tuiste van die
DIE MAROELABOS VAN TSHIPISE-”DUIN” » Berig op volgende bladsy
DIE INVLOED VAN SWART TURF OP BOOMDIVERSITEIT
Die invloed van swart turf op boomdiversiteit
te Malgas, Noordoostelike Springbokvlakte
Nico Hager
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blaasdoring (Acacia luederitzii var. retinens) en
‘n paar ander wat dié grondsoort se gelyke is.
Die agtervoegsel “-pan” in Immerpan verwys nie
na ‘n pan in die werklike sin van die woord nie.
Volgens Wagner (1927) is daar geen panne op die
basaltgedeeltes van die Vlakte nie: “The complete
absence of pans is the more remarkable as they
are fairly common on the sand-bults.” ‘n Ondersoek
van die S.A. 1:50 000 Topo-kadastrale kaarte van
die gebied bevestig inderdaad hul afwesigheid.
Desondanks is daar talle plase op die turfvlaktes
met “pan”-name, bv. Klippan (521), Rooipan (508),
Vlakpan (509), Mooipan (519), Turfpan (943),
Zandpan (1048) en Kalkpan (127). Immerpan is ‘n
spoorweghalte op Brakfontein (152). Waarskynlik
het hierdie ou plaasname uit die dae van die ZAR
hul oorsprong in die vlak, breë, stadigvloeiende
waterlope, wat na groot reëns soos panne lyk.
Nie elke boom wat op ander grondsoorte in die
omgewing gedy, aard egter op Malgas se swart
turf nie. As voorbeelde, uit die omgewing, van
bome wat glad nie op swart turf kan aanpas nie,
kan die vaalboom (Terminalia sericea) en die
wilde-sering (Burkea africana) genoem word.
Hierdie twee is ware sandliefhebbers. ‘n Boom
se verspreidingspotensiaal word beperk as ‘n
lewensbelangrike omgewingsfaktor buite sy
verdraagsaamheidsgrense val, of indien dit sy
vermoë om te kompeteer, strem (Van Wyk, 1982).
In hierdie geval is die grond, die swart turf, met sy
besondere chemiese en fisiese eienskappe, die
beperkende faktor.
Tog is daar bome, soos die fyndoring (Acacia
tenuispina), wat uitsluitlik met swart turf assosieer.
Sulke bome is turfspesialiste. Tussen die uiterstes
van turfliefhebbers en -haters is daar ook die
veelsydiges (generaliste) wat op meerdere
grondsoorte deug. As voorbeelde van sulke
bome, wat op Malgas voorkom, kan die swarthaak
(Acacia mellifera subsp. detinens) en witgat (Boscia
albitrunca) genoem word. Dit is gewoonlik bome
met groot verspreidingsgebiede.
Dat die swart turf die verspreiding van verreweg die
meeste van die omgewing se bome daarop inhibeer,
word deur die feite gestaaf. Op Malgas kom net
16 soorte voor, terwyl daar op Vuursteenlaagte,
5 kilometer daarvandaan, op sand, 73 is. Dié
opvallende verskil in diversiteit kan net toegeskryf
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DENDRON » No/Nr: 43 » November 2011