Thesis (MSc(For))--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Recognizing the biological significance of gaps, the South African Department of Water Affairs and
Forestry (DWAF) in 1989 initiated a Gap Dynamics Project in the indigenous forests of
Tsitsikamma (Eastern Cape, South Africa). This consists of three sub-projects: Koomansbos (9300
m2), created by a ground fire in 1989; Plaatbos (1600 m2), made by a Podocarpus falcatus (Thunb.)
R. Br. ex Mirb. (Podocarpaceae) windfall in 1994; and nine gaps of different sizes, artificially
created by selective tree felling in 1995: three small (100-150 m2), three medium (300-500 m2) and
three large (800-1000 m2). All the gaps were surveyed after creation and permanent plots were
established for subsequent monitoring. The current timber harvesting system practiced in South
African indigenous forests attempts to minimize gap size. It has been proposed by Euston-Brown et
al. (1996) that this practice is likely to benefit the more shade tolerant species, but may inhibit the
regeneration of less shade tolerant plants in the forest. Therefore, the present study aimed to verify
two hypotheses: gaps may close in a process that is determined by their size, their origin and the
plant species characteristics; soil quality might change inside those gaps. For the purpose of the
study, the gaps cited above were re-surveyed between 2002 and 2003. It was found that: 1) there
was little clear difference in the community structure of plant species between gaps of different
sizes and origins; as expected from the species-area relationship, large gaps had higher species
richness, plant diversity and herbaceous percentage cover than medium and small gaps; diversity
indices were higher in the large windfall gap than in the large fire and artificial gaps; generally,
context and stochastic events were largely more important in determining gap diversity and
regeneration than gap sizes and origins; 2) diversity indices in the gaps were higher than recorded
previously; 3) soil pH and Electrical Conductivity were respectively lower and higher inside the
gaps than adjacent to them; these variations were statistically significant. Present data on the
vegetation in the gaps were compared to past measurements, and future vegetation structure has
been predicted, as a function of current gap vegetation. Recommendations have been made for
sustainable management of the indigenous forest of Tsitsikamma. / AFRIKAANSE OPSOMMING: Voortspruitend uit die erkenning van die biologiese belang van gapings, het die Suid-Afrikaanse
Departement van Waterwese en Bosbou (DWB) in 1989 'n projek oor gapingsdinamika in die
inheemse woude van Tsitsikamma (Oos-Kaap, Suid-Afrika) geïnisieer. Dit bestaan uit drie
subprojekte: die gaping in Koomansbos (9300 m2) wat in 1989 deur 'n grondvuur geskep is; die
gaping in Plaatbos (1600 m2) wat veroorsaak is toe bome van die spesie Podocarpus falcatus
(Thunb.) R. Br. ex Mirb. (Podocarpaceae) in 1994 omgewaai is; en nege gapings van verskillende
groottes wat in 1995 kunsmatig deur geselekteerde boomkappery geskep is: drie is klein (100-150
m2), drie mediumgrootte (300-500 m2) en drie groot (800-1000 m2). Alle gapings is ná hulle
ontstaan opgemeet en ondersoek en permanente terreine is vir daaropvolgende monitering gevestig.
Die stelsel wat tans vir die oes van hout in Suid-Afrikaanse inheemse woude gebruik word, poog
om die grootte van gapings te minimaliseer. Euston Brown et al. (1996) doen aan die hand dat
hierdie praktyk spesies wat meer skaduweeverdraagsaam is waarskynlik sal bevoordeel, maar die
regenerasie van plante in die woud wat minder skaduweeverdraagsaam is, kan inhibeer. Hierdie
studie het dus ten doel gehad om twee hipoteses te verifieer: Gapings kan toegroei in 'n proses wat
deur hul grootte, oorsprong en die eienskappe van die plantspesies bepaal word; en die gehalte van
die grond binne daardie gapings kan verander. Die gapings waarna hierbo verwys is, is vir die doel
van hierdie studie tussen 2002 en 2003 weer gemonitor. Daar is bevind dat: 1) daar min duidelike
verskille was tussen die gemeenskapstruktuur van plantspesies tussen gapings van verskillende
groottes en oorsprong; soos van die verhouding tussen spesies en area verwag kan word, het groter
gapings 'n hoër spesierykheid, plantdiversiteit en persentasie niehoutagtige dekking as medium- en
klein gapings gehad; diversiteitsindekse was hoër in die groot Plaatbosgaping as in die groot
Koomansbosgaping of die kunsmatige gapings; in die algemeen was konteks en stochastiese
gebeure grootliks belangriker in die bepaling van gapingsdiversiteit en -regenerasie as
gapingsgrootte of -oorsprong; 2) diversiteitsindekse in die gapings was hoër as wat voorheen
aangeteken is; en 3) grond-pH en elektriese geleidingsvermoë was onderskeidelik laer en hoër binne
die gapings as neffens hulle; hierdie variasies was statisties beduidend. Huidige data oor die
plantegroei in die gapings is met vorige metings vergelyk, en 'n toekomstige plantegroeistruktuur is
as 'n funksie van huidige gapingsplantegroei voorspel. Aanbevelings is gemaak rakende die
volhoubare bestuur van Tsitsikamma se inheemse woud.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20916 |
| Date | 12 1900 |
| Creators | Ella, Ghislain |
| Contributors | Pepler, Dave, McGeoch, Melodie A., Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | vi, 107 leaves : ill., maps |
| Rights | Stellenbosch University |
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