Seed dynamics and seedling survival in mainland thicket of the Eastern Cape
- Weatherall-Thomas, Clayton Richard
- Authors: Weatherall-Thomas, Clayton Richard
- Date: 2009
- Subjects: Seeds -- Growth , Germination , Seedlings -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10601 , http://hdl.handle.net/10948/1048 , Seeds -- Growth , Germination , Seedlings -- South Africa -- Eastern Cape
- Description: Subtropical Thicket is the dominant vegetation biome in the Eastern Cape. Little regeneration through seedlings has been observed in Thicket. This is of serious concern, as Thicket has been degraded over large areas of its distribution. An understanding of the seed dynamics is necessary for any restoration project. A number of possible causes for the lack of seedlings were therefore investigated. Study sites were best classified according to the biogeographical regions of the Subtropical Thicket Ecosystem Planning (STEP) project. The seed bank of Thicket is dissimilar to the aboveground vegetation, as it lacks woody species and is dominated by herbs and grasses, making little contribution to the regeneration of Thicket species. An increase in canopy cover resulted in lower soil and air temperatures, as well as light, and an increase in litter depth. Seedling abundance and species richness increases with mean annual rainfall, with woody seedlings being dominant in the higher rainfall areas, and succulent species in the lower rainfall regions. Anemochorous species dominated the germinable seed bank, and zoochorous species were more prevalent underneath the canopy, compared to open areas, an indication of active seed dispersal. No germination was recorded in many Thicket species, and dormancy mechanisms were lacking in many of the species that did germinate. Immersion in hot water increased germination in the hard seeds of Acacia karroo, whereas shade enhanced germination in small seeded Burchellia bubalina. The response of seedlings of four Thicket species with varying distribution to shade and drought was studied. Ptaeroxylon obliquum and Aloe africana are drought tolerant species, whereas Burchellia bubalina and Rhus dentata were intolerant to low soil moisture. All four species were able to grow in deep shade, although Rhus dentata would be classified as a shade avoider, unlike the other three species that are shade tolerant. This results in the four species having different regeneration niches. It was concluded that dispersal and the lack of “safe sites” for seedlings were the main limitations to seedling establishment in Mainland Thicket.
- Full Text:
- Date Issued: 2009
- Authors: Weatherall-Thomas, Clayton Richard
- Date: 2009
- Subjects: Seeds -- Growth , Germination , Seedlings -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10601 , http://hdl.handle.net/10948/1048 , Seeds -- Growth , Germination , Seedlings -- South Africa -- Eastern Cape
- Description: Subtropical Thicket is the dominant vegetation biome in the Eastern Cape. Little regeneration through seedlings has been observed in Thicket. This is of serious concern, as Thicket has been degraded over large areas of its distribution. An understanding of the seed dynamics is necessary for any restoration project. A number of possible causes for the lack of seedlings were therefore investigated. Study sites were best classified according to the biogeographical regions of the Subtropical Thicket Ecosystem Planning (STEP) project. The seed bank of Thicket is dissimilar to the aboveground vegetation, as it lacks woody species and is dominated by herbs and grasses, making little contribution to the regeneration of Thicket species. An increase in canopy cover resulted in lower soil and air temperatures, as well as light, and an increase in litter depth. Seedling abundance and species richness increases with mean annual rainfall, with woody seedlings being dominant in the higher rainfall areas, and succulent species in the lower rainfall regions. Anemochorous species dominated the germinable seed bank, and zoochorous species were more prevalent underneath the canopy, compared to open areas, an indication of active seed dispersal. No germination was recorded in many Thicket species, and dormancy mechanisms were lacking in many of the species that did germinate. Immersion in hot water increased germination in the hard seeds of Acacia karroo, whereas shade enhanced germination in small seeded Burchellia bubalina. The response of seedlings of four Thicket species with varying distribution to shade and drought was studied. Ptaeroxylon obliquum and Aloe africana are drought tolerant species, whereas Burchellia bubalina and Rhus dentata were intolerant to low soil moisture. All four species were able to grow in deep shade, although Rhus dentata would be classified as a shade avoider, unlike the other three species that are shade tolerant. This results in the four species having different regeneration niches. It was concluded that dispersal and the lack of “safe sites” for seedlings were the main limitations to seedling establishment in Mainland Thicket.
- Full Text:
- Date Issued: 2009
An anatomical investigation of jointed cactus (Opuntia aurantiaca, Lindley) with germination tests, and observations on the movements of the stomata
- Authors: Archibald, E E A
- Date: 1936
- Subjects: Cactus -- Anatomy , Opuntia , Stomata , Germination
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4264 , http://hdl.handle.net/10962/d1013444
- Description: From Introduction: In 1934 the Government started an active campaign on the eradiction of Jointed Cactus. This plant was causing considerable damage to the farms and commonages of the Eastern Province, and was spreading at an alarming rate. The Officer in Charge of eradication, Mr E. du Toit, was stationed at Grahamstown which is fairly centrally situated in the infested area. In 1935 Dr A. Leemann of the Division of Plant Industry made his headquarters at Rhodes University College.
- Full Text:
- Date Issued: 1936
- Authors: Archibald, E E A
- Date: 1936
- Subjects: Cactus -- Anatomy , Opuntia , Stomata , Germination
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4264 , http://hdl.handle.net/10962/d1013444
- Description: From Introduction: In 1934 the Government started an active campaign on the eradiction of Jointed Cactus. This plant was causing considerable damage to the farms and commonages of the Eastern Province, and was spreading at an alarming rate. The Officer in Charge of eradication, Mr E. du Toit, was stationed at Grahamstown which is fairly centrally situated in the infested area. In 1935 Dr A. Leemann of the Division of Plant Industry made his headquarters at Rhodes University College.
- Full Text:
- Date Issued: 1936
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