Mangrove Swamps in South Africa

Macnae, William

doi:10.2307/2257502

Cited by 97 publications

(40 citation statements)

References 7 publications

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“…Although old trees of B. gymnorrhiza have been recorded with a height of approximately 20 metres in South Africa (Macnae, 1963), this is unusual as the majority are of the size measured in this study or only slightly taller . Our mangroves are also of limited extent, man's influence on these communities in the past has been intense, and, particularly in the southern areas where they are nearing the limit of their distribution, growth is slower than under more favourable tropical conditions .…”

Section: Individual Tree Biomassmentioning

confidence: 54%

Forest structure and biomass of mangroves in the Mgeni estuary, South Africa

1995

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Forest structure and biomass were determined in a mangrove stand dominated by Bruguiera gymnorrhiza (L.) Lam . Trees in 5 m 2 sample plots were harvested at ground level and then further cut into 1 m strata for separation into living wood, dead wood, leaves, reproductive material and pneumatophores . Mean above-ground living biomass was calculated at 94 .49±7 .83 t dry matter ha 1, while dead wood contributed a mean mass of 7 .63±0 .89 t dry matter ha-' . Excavations of roots yielded a below-ground biomass of 9 .67 t dry matter ha 1 which represented only 9 .8% of the above-ground value. There was a mean density of 4700 living stems ha -1 with plant heights ranging from 0 .57 m to 5 .80 m . Mean LAI was 4 .95±0 .80 . As a basis for estimating standing biomass, regression lines were fitted to biomass values from individual trees of B. gymnorrhiza and Avicennia marina (Forssk .) Vierh . of various sizes . A comparison of these relationships with methods used by previous workers for estimating biomass suggests that most other methods cannot be applied without modification for local stands of mangroves .

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Section: Individual Tree Biomassmentioning

confidence: 54%

Forest structure and biomass of mangroves in the Mgeni estuary, South Africa

1995

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“…A list of crab species is available for most East African countries, but only a few notes are given on their ecology (Somalia: Vannini and Valmori 1981 a, b;Madagascar: Crosnier 1965;Tanzania: Hartnoll 1975;South Africa: Barnard 1950), with the exception of South Africa (Macnae 1963) and Mocambique (Macnae and Kalk 1969) where the subject has been treated extensively. Few studies have dealt with Cardisoma carnifex and Sesarma meinerti, two of the most common African mangrove crabs (C. carnifex in Aldabra: Grubb 1971, Alexander 1979 S. meinerti in Mocambique : Cott 1929; both species in Kenya: Hogue and Bright 1971).…”

Section: Introductionmentioning

confidence: 99%

Feeding and burrowing ecology of two East African mangrove crabs

1991

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Abstract. The behavior and ecology of two mangrove crabs, Sesarma meinerti De Man, 1887 and Cardisoma carnifex (Herbst, 1794) were investigated at the beginning of the rainy season (October-November 1988) at Mida Creek, Kenya. Both species occupy upper intertidal levels, above mean high-water neap, and completely overlap in their zonation. Each burrow lasts ca. 3 wk, with no significant difference between the species. Both are more active around dusk and dawn and also follow a similar trend in their foraging activity, but differ in that burrowing is mainly diurnal in C. carnifex and nocturnal in S. meinerti. A hierarchy of food preference, established by offering C. carnifex and S. meinerti leaves of five mangrove species, proved similar for both, with Bruguiera gymnorhiza ranking first and Avicennia marina last, but significant only for C. carnifex. A rough estimate of the amount of litter consumed by these two species and of the soil mixed up by their burrowing activity indicates that they play a role of primary importance in the ecology of East African mangroves.

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“…and Xylocarpus granatum. The latter three species are only found north of this area, e.g., in Mozambique, Tanzania and Kenya (MacNae 1963).…”

Section: Introductionmentioning

confidence: 93%

“…In Africa, with estimated rates of loss of between 1500 and 2000 ha per annum by harvesting and the expansion of agriculture, the loss of mangroves in the Transkei region by comparison appears insignificant. This does not mean that the South African mangroves should be ignored, they should be protected because of their unique species composition (MacNae 1963) and because they occur at the southernmost limit of their distribution (MacNae 1963;Saenger and Bellan 1995;Spalding et al 1997).…”

Section: Livingmentioning

confidence: 99%

The distribution and state of mangroves along the coast of Transkei, Eastern Cape Province, South Africa

Adams

Colloty

Bate

2004

Wetlands Ecol Manage

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The mangrove communities along the coastline of the former Transkei, now part of the Eastern Cape Province, have not been looked at in detail since Ward and Steinke's survey in 1982. Mangroves previously occurred in 17 estuaries but were now found in only 14 of the 76 estuaries visited, with a complete loss of mangroves evident in the Mnyameni, Mzimvubu and Bulungula estuaries amounting to 7.5 ha. Total mangrove loss amounted to 17.6 ha which represents a 6.5% loss over 17 years or 1.04 ha per annum. Tree cover had increased by 16.15 ha in eight other estuaries. This increase could be attributed to the inaccessibility of mangrove stands or to protection afforded by provincial nature reserves and hotel resorts. No new mangrove stands were recorded, although Steinke (pers. comm.) has recently recorded mangroves along the north bank of the Kei River. There has been little change in mangrove species composition in the different estuaries over the past 17 years. Total mangrove loss amounted to 17.6 ha which represents a 6.5% loss over 17 years or 1.04 ha per annum and the species recorded included Avicennia marina, Bruguiera gymnorhiza and Rhizophora mucronata. The mangrove fern Acrostichum aureum L. was recorded for the first time in the Mkozi estuary. Tree density for all estuaries was between 10 and 2594 trees ha À1 . The Mngazana and Mntafufu estuaries had the highest tree densities of 2594 and 1402 trees ha À1 respectively, typical of riverine mangrove forests. Fringe mangroves were evident in most other systems. Removal of trees for wood has the greatest impact on mangrove cover. Fringe mangrove stands are particularly accessible to harvesters. Only 6% of the current area of trees is afforded some protection in conservation areas. The Mdumbi, Mzamba and Kobonqaba estuaries receive no conservation protection and harvesting has resulted in more than 50% of the trees being removed. The density of dead tree stumps was greater than the number of living trees and no seedlings or juvenile trees were found. Further removal of mangroves within the estuaries south of the Mzimvubu River is expected in the fringe mangroves, as most are unprotected and easily accessible.

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Mangrove Swamps in South Africa

Cited by 97 publications

References 7 publications

Forest structure and biomass of mangroves in the Mgeni estuary, South Africa

Forest structure and biomass of mangroves in the Mgeni estuary, South Africa

Feeding and burrowing ecology of two East African mangrove crabs

The distribution and state of mangroves along the coast of Transkei, Eastern Cape Province, South Africa

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