The plant ecology of seasonally flooded areas of the Pongolo River floodplain, with particular reference to Cynodon dactylon (l.) Pers. / by Hilton Dalton Furness.

By: Furness, Hilton Dalton.
Material type: materialTypeLabelBookPublisher: Pietermaritzburg : University of Natal, 1981Description: 2 volumes (ii, 132 + [4], 53 leaves) : illustrations, maps ; 30 cm.Subject(s): FLOODPLAINS | LAKES | SHALLOW WATER | RIVERS | PHYTOPLANKTON | SOUTH AFRICA | EPIPHYTES | GRASSLANDS | MACROPHYTES | AQUATIC PLANTS | CYNODON DACTYLON | PLANT ECOLOGY | THESESHoldings: GRETA POINT: 574.5(680) FUR Online resources: Click here to access online
Contents:
Summary -- CHAPTER 1. Introduction -- VOLUME 1 CONTENTS -- CHAPTER 2. Review of Pertinent Literature -- 2.1 Floodplain Geomorphology -- 2.1.1 Floodplain formation -- 2.1.2 Floodplain features -- 2.2 Floodplain Hydrology -- 2.3 Physico-Chemical Conditions -- 2.3.1 Oxygen levels -- 2.3.2 Conductivity and pH -- 2.3.3 Nutrients -- 2.4 Floodplain Flora: its importance in the functioning of floodplain systems -- 2.4.1 Submerged and floating plants -- 2.4.1.1 Phytoplankton -- 2.4.1.2 Epiphytes -- 2.4.1.3.1 Rooted aquatic macrophytes -- 2.4.1.3.2 Floating aquatic plants -- 2.4.2 Plants of the seasonally inundated areas -- 2.5 Floodplain Research: present status and future requirements -- CHAPTER 3. Materials and Methods -- 3.1 Classification and Ordination of the Vegetation -- 3.1.1 Choice of the Braun-Blanquet method -- 3.1.2 Application of the method -- 3.1.2.1 Collection of field data -- 3.1.2.2 Synthesis of data -- 3. Functioning of the Cynodon dactylon Community --- 3.2.1 Measurement of standing crop and amount removed by grazing -- 3.2.2 Calculation of mean crop growth rate -- 3.2.3 Measurement of nutrient content -- 3.2.4 Integration of processes taking place on the floodplain -- 3.2.5 Determination of water status -- 3.2.5.1 Soil moisture content -- 3.2.5.2 Measurement of soil matric potential -- 3.2.5.3 Measurement of xylem pressure potential -- 3.2.5.4 Measurement of vapour pressure deficit -- 3.2.6 Measurement of decomposition rates -- CHAPTER 4. Description of the Study Area -- 4.1 Location -- 4.2 Geology and Geomorphology -- 4.3 Climate -- 4.4 Hydrology -- 4.4.1 Hydrology prior to the construction of the Pongolapoort Dam -- 4.4.2 Hydrology after construction of the Pongolapoort Dam -- 4.4.3 Hydrology between the Pongolapoort Dam and Mocambique -- 4.5 Inhabitants -- 4.6 Vegetation -- CHAPTER 5. The Plant Communities -- 5.1 Results -- 5.1.1 The Communities of the high-lying areas -- 5.1.1.1 The Ficus sycomorus - Rauvolfia caffra Community -- 5.1.1.1.1 The Ficus sycomorus - Eriochloa meyeriana (Nees) Pilg. Sub-community -- 5.1.1.1.2 The Ficus sycomorus - Acacia xanthophloea Sub-community -- 5.1.1.2 The Acacia xanthophloea - Dyschoriste depressa Community -- 5.1.1.3 Interrelationships -- 5.1.2 The Communities of the low-lying areas -- 5.1.2.1 The Phragmites australis Community -- 5.1.2.2 The Phragmites mauritianus Community -- 5.1.2.3 The Cyperus fastigiatus - Echinochloa pyramidalis Community -- 5.1.2.4 Interrelationships -- 5.1.3 The Community of the intermediate areas -- 5.1.3.1 The Cynodon dactylon Community -- 5.1.3.2 Interrelationships -- 5.1.4 Releves of undetermined affinity -- 5.2 Discussion -- 5.3 Conclusions and Future Research Priorities -- CHAPTER 6. Crop Growth Rate of Cynodon dactylon in Response to Exposure and Grazing -- 6.1 Results -- 6.1.1 Crop growth rate in the absence of grazing -- 6.1.1.1 Grazeable fraction -- 6.1.1.2 Ungrazeable fraction -- 6.1.2 Crop growth rate in the presence of grazing -- 6.1.2.1 Grazeable fraction -- 6.1.2.2 Ungrazeable fraction -- 6.2 Discussion -- 6.3 Implications for the Floodplain -- 6.4 Conclusions and Future Research Priorities -- CHAPTER 7. Nutrient Status of Cynodon dactylon in Response to Exposure and Grazing -- 7.1 Results -- 7.1.1 Changes in nutrient concentration during exposure and grazing -- 7.1.1.1 Grazeable fraction -- 7.1.1.2 Ungrazeable fraction -- 7.1.2 Removal of nutrients by grazers from the area around Namanini lake -- 7.1.3 Nutrients contained in the standing crop of C. dactylon around Namanini lake -- 7.2 Discussion -- 7.2.1 Effects of exposure on nutrient concentration -- 7.2.2 Effects of grazing on nutrient concentration -- 7.2.3 Comparison of nutrient concentrations in C. dactylon on the floodplain with that in other areas -- 7.2.4 The effect of nutrient removal by grazing on the standing stock of nutrients -- 7.3 Implications for the Floodplain -- 7.4 Conclusions and Future Research Priorities -- CHAPTER 8. Water Stress as a Factor Influencing Growth of Cynodon dactylon -- 8.1 Results -- 8.1.1 Precipitation -- 8.1.2 Vapour pressure deficit (VPD) -- 8.1.3 Soil characteristics: field capacity (FC) and permanent wilting point (PWP) -- 8.1.4 Xylem pressure potential (P) -- 8.2 Discussion -- 8.2.1 Effects of exposure on water stress -- 8.2.2 Effects of water stress on growth and nutrient content -- 8.2.3 Effects of grazing on water stress -- 8.3 Implications for the Floodplain -- 8.4 Conclusions and Future Research Priorities -- CHAPTER 9. Decomposition of Cynodon dactylon -- 9.1 Results -- 9.1.1 Patterns and rates of loss of organic and mineral fractions from harvested C. dactylon material -- 9.1.2 Patterns and rates of loss of nutrients from harvested C. dactylon material -- 9.1.3 Changes in the nutrient content of the inundated above-ground fraction of C. dactylon -- 9.2 Discussion -- 9.3 Implications for the Floodplain -- 9.4 Conclusions and Future Research Priorities -- CHAPTER 10. General Discussion and Conclusions -- 10.1 Introduction -- 10.2 Conceptual Model -- 10.2.1 Winter conditions -- 10.2.2 Summer conditions -- 10.3 Management Proposals -- 10.3.1 Water release programme for the Pongolapoort Dam -- 10.4 Conclusions -- Acknowledgements -- References -- Personal Communications: Addresses.
Dissertation note: Thesis (Ph.D. (Botany)) - University of Natal, Pietermaritzburg, 1981. Summary: The impounding of the waters of the Pongolo river, upstream of its floodplain on the Mocambique coastal plain, may adversely affect the functioning of the floodplain system. A multidisciplinary study of the functioning of the floodplain was initiated to provide a basis for the development of a management strategy for the floodplain. The study reported in this dissertation considered the flood dependence and functioning of the vegetation of the seasonally inundated area. The vegetation was mapped and the communities ordinated, according to the Braun-Blanquet technique, in relation to their positions relative to high flood level (HFL) and the level of the water after flood subsidence (i.e. maximum retention level, MRL). Community distribution was shown to be strictly determined by both the height of the floods and by the MRL. It was concluded that periodic floods are essential for the maintenance of the communities. The Cynodon dactylon (L.) Pers. Community, which forms extensive meadows in the zone of periodic inundation, was studied in detail. As the water level receded during winter, productivity was high (up to 23 kg ha¯¹ d¯¹1 dry mass) and a palatable sward was produced. This is heavily grazed by domestic stock, but as the soil dries out and water stress becomes significant, production decreases, C. dactylon becomes less palatable, and grazing shifts to newly exposed areas. The shift in grazing allows the build up of a large standing crop of both grazeable and ungrazeable (below ground and stolons) material. At the time of inundation by the next floods c. 910 kg ha¯¹ of dry mass, c. 17 kg ha¯¹ nitrogen and c. 2 kg ha¯¹ phosphorus have been removed by grazers. It is concluded that this production, which is flood dependent, forms an important supplement to stock grazing during winter. It is suggested that this source of grazing could be stimulated by irrigation during winter. Cynodon dactylon is shown to decompose rapidly during inundation, losing half of its mass and nutrients in c . 28 days. It therefore represents a major energy and nutrient input during the aquatic phase. The extent to which it is grazed during submergence is unknown. The nutrient input is derived ultimately from the soils of the inundated areas and, since nutrients are being removed by both terrestrial grazers and flushing, continued production is reliant upon the annual sediment load reaching the floodplain. Most of the sediment load will now be deposited in the impoundment, and fertilization may be necessary to maintain productivity. The response of C. dactylon to the seasonal fluctuations in water level are used to formulate proposals for water release from the dam. These include proposals for the short-term, i.e. until the demand for irrigation water conflicts with the requirements of the floodplain, and for the long-term, when less water will be available for the floodplain.
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Item type Current location Call number Copy number Status Date due Barcode
BOOK BOOK WELLINGTON
BOOKS
574.5(680) FUR VOL. 2 1 Available B020361
BOOK BOOK WELLINGTON
BOOKS
574.5(680) FUR VOL. 1 1 Available B020360

Submitted in partial fulfilment of the Degree of Doctor of Philosophy in the Department of Botany, University of Natal, Pietermaritzburg.

Vol. 1, Text -- Vol. 2, Figures, tables and plates.

Thesis (Ph.D. (Botany)) - University of Natal, Pietermaritzburg, 1981.

Includes bibliographical references

Summary -- CHAPTER 1. Introduction -- VOLUME 1 CONTENTS -- CHAPTER 2. Review of Pertinent Literature -- 2.1 Floodplain Geomorphology -- 2.1.1 Floodplain formation -- 2.1.2 Floodplain features -- 2.2 Floodplain Hydrology -- 2.3 Physico-Chemical Conditions -- 2.3.1 Oxygen levels -- 2.3.2 Conductivity and pH -- 2.3.3 Nutrients -- 2.4 Floodplain Flora: its importance in the functioning of floodplain systems -- 2.4.1 Submerged and floating plants -- 2.4.1.1 Phytoplankton -- 2.4.1.2 Epiphytes -- 2.4.1.3.1 Rooted aquatic macrophytes -- 2.4.1.3.2 Floating aquatic plants -- 2.4.2 Plants of the seasonally inundated areas -- 2.5 Floodplain Research: present status and future requirements -- CHAPTER 3. Materials and Methods -- 3.1 Classification and Ordination of the Vegetation -- 3.1.1 Choice of the Braun-Blanquet method -- 3.1.2 Application of the method -- 3.1.2.1 Collection of field data -- 3.1.2.2 Synthesis of data -- 3. Functioning of the Cynodon dactylon Community --- 3.2.1 Measurement of standing crop and amount removed by grazing -- 3.2.2 Calculation of mean crop growth rate -- 3.2.3 Measurement of nutrient content -- 3.2.4 Integration of processes taking place on the floodplain -- 3.2.5 Determination of water status -- 3.2.5.1 Soil moisture content -- 3.2.5.2 Measurement of soil matric potential -- 3.2.5.3 Measurement of xylem pressure potential -- 3.2.5.4 Measurement of vapour pressure deficit -- 3.2.6 Measurement of decomposition rates -- CHAPTER 4. Description of the Study Area -- 4.1 Location -- 4.2 Geology and Geomorphology -- 4.3 Climate -- 4.4 Hydrology -- 4.4.1 Hydrology prior to the construction of the Pongolapoort Dam -- 4.4.2 Hydrology after construction of the Pongolapoort Dam -- 4.4.3 Hydrology between the Pongolapoort Dam and Mocambique -- 4.5 Inhabitants -- 4.6 Vegetation -- CHAPTER 5. The Plant Communities -- 5.1 Results -- 5.1.1 The Communities of the high-lying areas -- 5.1.1.1 The Ficus sycomorus - Rauvolfia caffra Community -- 5.1.1.1.1 The Ficus sycomorus - Eriochloa meyeriana (Nees) Pilg. Sub-community -- 5.1.1.1.2 The Ficus sycomorus - Acacia xanthophloea Sub-community -- 5.1.1.2 The Acacia xanthophloea - Dyschoriste depressa Community -- 5.1.1.3 Interrelationships -- 5.1.2 The Communities of the low-lying areas -- 5.1.2.1 The Phragmites australis Community -- 5.1.2.2 The Phragmites mauritianus Community -- 5.1.2.3 The Cyperus fastigiatus - Echinochloa pyramidalis Community -- 5.1.2.4 Interrelationships -- 5.1.3 The Community of the intermediate areas -- 5.1.3.1 The Cynodon dactylon Community -- 5.1.3.2 Interrelationships -- 5.1.4 Releves of undetermined affinity -- 5.2 Discussion -- 5.3 Conclusions and Future Research Priorities -- CHAPTER 6. Crop Growth Rate of Cynodon dactylon in Response to Exposure and Grazing -- 6.1 Results -- 6.1.1 Crop growth rate in the absence of grazing -- 6.1.1.1 Grazeable fraction -- 6.1.1.2 Ungrazeable fraction -- 6.1.2 Crop growth rate in the presence of grazing -- 6.1.2.1 Grazeable fraction -- 6.1.2.2 Ungrazeable fraction -- 6.2 Discussion -- 6.3 Implications for the Floodplain -- 6.4 Conclusions and Future Research Priorities -- CHAPTER 7. Nutrient Status of Cynodon dactylon in Response to Exposure and Grazing -- 7.1 Results -- 7.1.1 Changes in nutrient concentration during exposure and grazing -- 7.1.1.1 Grazeable fraction -- 7.1.1.2 Ungrazeable fraction -- 7.1.2 Removal of nutrients by grazers from the area around Namanini lake -- 7.1.3 Nutrients contained in the standing crop of C. dactylon around Namanini lake -- 7.2 Discussion -- 7.2.1 Effects of exposure on nutrient concentration -- 7.2.2 Effects of grazing on nutrient concentration -- 7.2.3 Comparison of nutrient concentrations in C. dactylon on the floodplain with that in other areas -- 7.2.4 The effect of nutrient removal by grazing on the standing stock of nutrients -- 7.3 Implications for the Floodplain -- 7.4 Conclusions and Future Research Priorities -- CHAPTER 8. Water Stress as a Factor Influencing Growth of Cynodon dactylon -- 8.1 Results -- 8.1.1 Precipitation -- 8.1.2 Vapour pressure deficit (VPD) -- 8.1.3 Soil characteristics: field capacity (FC) and permanent wilting point (PWP) -- 8.1.4 Xylem pressure potential (P) -- 8.2 Discussion -- 8.2.1 Effects of exposure on water stress -- 8.2.2 Effects of water stress on growth and nutrient content -- 8.2.3 Effects of grazing on water stress -- 8.3 Implications for the Floodplain -- 8.4 Conclusions and Future Research Priorities -- CHAPTER 9. Decomposition of Cynodon dactylon -- 9.1 Results -- 9.1.1 Patterns and rates of loss of organic and mineral fractions from harvested C. dactylon material -- 9.1.2 Patterns and rates of loss of nutrients from harvested C. dactylon material -- 9.1.3 Changes in the nutrient content of the inundated above-ground fraction of C. dactylon -- 9.2 Discussion -- 9.3 Implications for the Floodplain -- 9.4 Conclusions and Future Research Priorities -- CHAPTER 10. General Discussion and Conclusions -- 10.1 Introduction -- 10.2 Conceptual Model -- 10.2.1 Winter conditions -- 10.2.2 Summer conditions -- 10.3 Management Proposals -- 10.3.1 Water release programme for the Pongolapoort Dam -- 10.4 Conclusions -- Acknowledgements -- References -- Personal Communications: Addresses.

The impounding of the waters of the Pongolo river, upstream of its floodplain on the Mocambique coastal plain, may adversely affect the functioning of the floodplain system. A multidisciplinary study of the functioning of the floodplain was initiated to provide a basis for the development of a management strategy for the floodplain. The study reported in this dissertation considered the flood dependence and functioning of the vegetation of the seasonally inundated area. The vegetation was mapped and the communities ordinated, according to the Braun-Blanquet technique, in relation to their positions relative to high flood level (HFL) and the level of the water after flood subsidence (i.e. maximum retention level, MRL). Community distribution was shown to be strictly determined by both the height of the floods and by the MRL. It was concluded that periodic floods are essential for the maintenance of the communities. The Cynodon dactylon (L.) Pers. Community, which forms extensive meadows in the zone of periodic inundation, was studied in detail. As the water level receded during winter, productivity was high (up to 23 kg ha¯¹ d¯¹1 dry mass) and a palatable sward was produced. This is heavily grazed by domestic stock, but as the soil dries out and water stress becomes significant, production decreases, C. dactylon becomes less palatable, and grazing shifts to newly exposed areas. The shift in grazing allows the build up of a large standing crop of both grazeable and ungrazeable (below ground and stolons) material. At the time of inundation by the next floods c. 910 kg ha¯¹ of dry mass, c. 17 kg ha¯¹ nitrogen and c. 2 kg ha¯¹ phosphorus have been removed by grazers. It is concluded that this production, which is flood dependent, forms an important supplement to stock grazing during winter. It is suggested that this source of grazing could be stimulated by irrigation during winter. Cynodon dactylon is shown to decompose rapidly during inundation, losing half of its mass and nutrients in c . 28 days. It therefore represents a major energy and nutrient input during the aquatic phase. The extent to which it is grazed during submergence is unknown. The nutrient input is derived ultimately from the soils of the inundated areas and, since nutrients are being removed by both terrestrial grazers and flushing, continued production is reliant upon the annual sediment load reaching the floodplain. Most of the sediment load will now be deposited in the impoundment, and fertilization may be necessary to maintain productivity. The response of C. dactylon to the seasonal fluctuations in water level are used to formulate proposals for water release from the dam. These include proposals for the short-term, i.e. until the demand for irrigation water conflicts with the requirements of the floodplain, and for the long-term, when less water will be available for the floodplain.

GRETA POINT: 574.5(680) FUR

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