C. J. Geldenhuys

Native forest regeneration in pine and eucalypt plantations in Northern Province, South Africa

Abstract Commercial plantations in South Africa have been established mainly in grasslands adjacent to native forest which occur as small, scattered patches, restricted to valleys and scarps by regular fires in the adjacent fire-prone grasslands. Understorey vegetation was sampled in plantation stands of different age of Pinus patula, and old stands of P. elliottii, P. taeda and Eucalyptus saligna, growing on the forest margin. The study was done in two areas in Northern Province, South Africa (23°S to 25°S, and 30°E to 31°E): Woodbush-De Hoek along the Eastern Escarpment, and Entabeni on Soutpansberg mountains. The area receives 1200 to 1900 mm rain per annum, mainly during summer. Two hypotheses were tested: understorey colonisation by native plant species is strongly influenced by the overhead plantation species; and abundance and diversity of indigenous woody and herbaceous species increase with increasing stand age. A total of 170 species were recorded on 62 plots of 78.5 m2 each, and included all major growth forms present in the surrounding forest, except epiphytes. Trees were represented by 62 species, but only 18% of these occurred in more than 10% of the plots. Seventy-two percent of the 95 tree, shrub and climber species are animal-dispersed but only 22% of the animal-dispersed species occur in more than 10% of the plots. Mean clean bole length of the plantation stand gave the best regression coefficients with species richness, stem density, mean DBH and mean height of the woody regeneration, all of which increased with stand age. There was no clear pattern in understorey species composition among the different plantation species. Site factors such as substrate (geology) and temperature (altitude and radiation index) had a strong correlation with species composition and density of understorey vegetation. The results do demonstrate a useful successional process which could be used to achieve specific management objectives at relatively low costs. Potential applications of this succession process are manipulation of tree stands (commercial plantations or invader plants) to restore native forest biodiversity, control of understorey weeds in commercial plantations, and growing of useful crops under tree canopies.

Distribution, Size and Ownership of Forests in the Southern Cape

SYNOPSIS Indigenous forest of the southern Cape as delimited on 1:50 000 maps was analysed for distribution, size and ownership in six landscape zones: mountains, foothill, coastal platform, river valley, coastal scarp and dunes. I tested the hypothesis that forest distribution in the study area was limited by annual rainfall below 500 mm and not by geology. A total of 908 forest patches with size ranging from 0,3 ha to 25 706 ha covering a total area of 60 561 ha were analysed. Annual rainfall in areas where forest persists ranges between 500 and 1 220 mm, but the size and distribution of forests shows no relationship to total rainfall (above 500 mm), or to geology. The largest forests cover the foothills, coastal platform, river valleys and coastal scarp. The Goudveld-Diepwalle-Harkerville forest is the largest single, continuous forest in southern Africa and covers all landscape zones except dunes. By contrast the mountains have the largest number of forests but these are of relatively small mean area....

The Blackwood Group System: its relevance for sustainable forest management in the southern Cape.

SYNOPSIS The invasion status of Australian blackwood, Acacia melanoxylon, is assessed against its value as a commercial tree in the southern Cape forests. The species was introduced from Australian rain forests and planted extensively in the southern Cape forests since 1909. It has since become well established in the forests, and invaded open areas outside the forest. However, it is also a useful and valuable timber tree which contributes more than 60% of both the timber volume and revenue obtained from the forest. A Blackwood Group System was established in the forest since 1968 in which the tree was planted in pure stands in the forest gaps caused by the felling of large trees. This study comprised various investigations to assess the invasion status of the species in the forests and to determine under what conditions it poses a threat to the forest. The results show that A. melanoxylon occurs in all the main forests throughout the southern Cape. It has the characteristics of an aggressive invader plan...

Performance of Podocarpus falcatus Provenances in South Africa

SYNOPSIS Podocarpus falcatus, a canopy tree of the mixed evergreen forests in South Africa, is planted in riparian zones in commercial forestry areas. In 1982 provenance trials were initiated to evaluate the performance of 11 provenances in three experimental sites: De Hoek in the northeastern Transvaal; Frankfort in the eastern Transvaal; and Witfontein in the southern Cape. Only five provenances were planted in all three sites. The great variation in fruit and seed mass could not be related to latitudinal or locality differences of origin of the provenances. Germination capacity ranged between 3 and 94%, but the differences were related to periodically unsuitable environmental conditions during fertilisation of the ovule rather than genetic variation. For most provenances the germination rate over time followed the normal pattern of a sharp increase in germination during October, about 50 weeks after sowing. However, seed from the sub tropical Zululand coast germinated after 10 weeks and continued to ge...

Floristic and Structural Composition of Hanglip Forest in the Soutpansberg, Northern Transvaal

SYNOPSIS The closed, evergreen forest of 363 ha was sampled by means of 62 circular plots of 0,04 ha, distributed in a grid pattern. TWINSPAN classification separated the forest into regrowth forest with two forest types, and mature forest with four forest types. The types differ from each other in terms of floristics, overall size of the trees and regeneration, stand density and basal area, and diameter class distribution of selected species. The types reflect both site conditions and recovery from (or absence of) disturbance. The regrowth forest of the lower, eastern portion have probably recovered from earlier settlements of the Venda tribe who practised iron ore smelting and agriculture towards the end of the 19th century. A species list is appended.

Regeneration Patterns in Planted and Natural Forest Stands Near Knysna, Southern Cape

SYNOPSIS The Diepwalle Arboretum was established in 1926 and consists of a cultivated and uncultivated section. The cultivated section consists of pure stands while the uncultivated section contains both pure and mixed stands. In the cultivated section the understorey vegetation was slashed regularly until 1969 after which natural regeneration was allowed. In 1985 the regeneration was sampled in the natural forest and underneath each of 23 stands in the Arboretum. The following regeneration patterns were observed: • Species composition and abundance of regeneration were similar in the natural forest and uncultivated stands, which were different from those in the cultivated stands; • Diversity is highest in the most recently disturbed stands; • Pure stands inhibit regeneration of the same species completely while “other” seedlings are allowed to regenerate extensively.

Inventory of Indigenous Forest and Woodland in Southern Africa

SYNOPSIS An inventory is an important component of a series of activities to ensure the sustained use of natural forest and woodland resources. Three levels of inventories are considered: national level to determine general forest policy: regional level to provide a basis for integrated multiple-use management: and local level for detailed working plans. Different approaches to mapping resource areas are discussed, with particular emphasis of the use of satellite imagery. Sampling design requirements are discussed with particular emphasis on accuracy and precision, stratification of the resource area. shape and size of the sampling units, random and systematic distribution of sampling units, sampling intensity and the allocation of sampling units to stratified vegetation units. Requirements for sampling variables, and analyses and presentation of inventory results are briefly discussed. Several examples are used from inventories conducted in forest and woodland in southern Africa.

Sustainable Harvesting of Timber from Woodlands in Southern Africa: Challenges for the Future

SYNOPSIS Woodlands covered > 50% of the land area in southern Africa, but only 57% remain today and only 7% occur in protected areas. Mean population density in the region is 17 people/km2 and urbanisation is increasing. In several countries subsistence agriculture is still the main contributor to the GDP. The main challenge in the region is to develop a sustainable contribution to the industry and service sectors of the economy from the woodland resources while improving the conservation status of the vegetation resources. A wide range of timber and non-timber products are harvested from the woodlands, often with no concern for the maintenance of the resource, or to optimise and economise the utilisation of the trees that are felled, or to pursue multiple-use systems. Very few species are utilised, and some of the harvested species are relatively rare, or are over-utilised, and the management systems to not favour their regeneration. Sustained-use management of woodlands require the maintenance of 1) the...

Floristic and Structural Composition of Wonderwoud Forest in the Wolkberg, North-Eastern Transvaal

SYNOPSIS The closed, evergreen forest of 450 ha was studied by means of a survey of 55 circular plots of 0,04 ha, distributed in a grid pattern. TWINSPAN classification separated the forest into four stand types: Olea capensis macrocarpa—Xymalos monospora—Syzygium gerrardii forest (types 1 and 2) and Cryptocarya liebertiana forest (types 3 and 4). The types differ from each other in terms of floristics, stem density, basal area, and diameter distribution of trees. Tree generation is generally sparse and small, and do not represent the present canopy composition. Regrowth species are generally lacking. A species list is appended.

Disjunctions and Distribution Limits of Forest Species in the Southern Cape

SYNOPSIS A total of 206 species reach their distribution limits within the southern Cape forests, or have disjunct distributions within this area and wider distributions outside. Biological variables (growth form, dispersal type) and habitat variables (forest type, moisture tolerance) are not significantly correlated with the drop-out of species, but all distribution variables (spread and abundance in study area, geographic origin) are. Species with a western distribution limit are concentrated in the Mossel Bay-George area. It is suggested that these western limits and the disjunctions west of Gouritz River and in the Knysna and Tsitsikamma forests relate to the major forest decline with the onset of the Late Pliocene marine regression. Species tolerant of drier conditions are concentrated in disjunct localities of dry high or scrub forest in the drier valleys around Mossel Bay and Plettenberg Bay, at Natures Valley, on the dunes around Sedgefield, and in the coastal areas of eastern Tsitsikamma. This p...