Defense of Master's Final Report


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Black Wattle (Acacia mearnsii, Fabaceae) represents one of the most important invasive alien species that have spread over large catchment areas in South Africa, with well documented effects on reducing water yield and in altering indigenous plant structure. Nationwide measures are being applied to eliminate this species, and different protocols are being evaluated for restoring heavily invaded areas, such as the rehabilitation site at the Lower Witteklip River in the Eastern Cape Province.
As a part of the Kouga River Rehabilitation Pilot Project, this study described four topics: (a) the degradation state of the area which was concluded that it was related to the presence of Black Wattle, (b) revegetation practices which were established as an experiment to evaluate the guilds which could be used to rehabilitate similar areas, defining as a priority from the early state of the experiment, to use a vast mix of species and densities as treatments, (c) effects of different biomass loads on burning and on the temperature to which soil was exposed in which it was observed that values dependent on the biomass load and not on the sampling site and (d) an assessment of the effects of fire and transformation of wood to chips, as methods to remove biomass left from clearing from the site which from the data available, there were not a definitive conclusion on which one of the treatments influenced on the results, mainly because of the lack of time for the soil seedbank to be fully germinated, and due to a mistake in the methodology by not segregating between the indigenous species group. This technical report also includes an assessment and some recommendations for the activities applied to the Lower Witteklip Rehabilitation Site and for the experiments.

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Defense of Master's Final Report

  1. 1. Technical Report of theRestoration of a section of the Witteklip River as part of the Pilot Project for Rehabilitation of the Kouga River<br />Master Oficial en Restauración de Ecosistemas<br />José David Díaz González<br />
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  4. 4. Problem: <br />Riparian areas invaded<br />effects on water yield<br />biodiversity loss <br />soil degradative processes<br />Situation of special concern for the Nelson Mandela Metropolitan Municipality<br />Problemdescription<br />
  5. 5. Cause of the problem: <br />Initial degradation derived from overgrazing<br />Current degradation caused by Black Wattle (Acacia mearnsii, Fabaceae) <br />Invasive alien plant for South Africa: Transformer status<br />Well documented effects on reducing water yield and in altering indigenous plant structure. <br />Persistent long-lived seeds favored by fire<br />Problemdescription<br />
  6. 6. Objectives<br /><ul><li>Of the Kouga RiparianRehabilitation Project</li></ul>Defining the most efficient protocol to clear and restore areas invaded with Black Wattle (Acacia mearnsii)<br />
  7. 7. Objectives<br /><ul><li>Of the Practicum</li></ul>Description of restoration activities in a section of the Witteklip River <br />Evaluate the possibilities of using fire or transformation of wood to chips, as methods for the disposal of the Black Wattle residues<br />
  8. 8. Sitedescription: General location<br />
  9. 9. Sitedescription: PhysicalEnvironment<br />
  10. 10. Sitedescription: PhysicalEnvironment<br />
  11. 11. The Lower Witteklip Restoration Area:<br />Witteklip River, which in turn is tributary of the Kouga river. <br />The Kouga River Catchment, represents a key water source for the Nelson Mandela Bay Metropolitan Municipality, <br />Sitedescription: Description of theriver<br />
  12. 12. Characterization of studysite:Longitudingalprofile of the Witteklip River<br />
  13. 13. General dyagnoseforthestudysiteProtocol for the Evaluation of the Ecological Status of Mediterranean rivers (RBP) <br />extremely degraded site with a very low quality <br />Site can have a partial success in holding aquatic biota with the initial situation observed<br />QBR index: evaluate riparian quality<br />IHF index: physical habitat<br />
  14. 14. General diagnose for study site: Digital image of site, 2001<br />
  15. 15. Review of the clearing and rehabilitationactivities in the study site<br /><ul><li>Clear-cutting all Acacia mearnsii trees
  16. 16. Application of herbicides to suppress resprouting
  17. 17. Wood stacks piling and drying for 3 months
  18. 18. Biomass burning
  19. 19. Restoration of plant cover
  20. 20. Restoration
  21. 21. Management of seedbank</li></li></ul><li>Experiments performed:Biomass burning<br />Assessment of temperature in first 5 cm of soil:<br />Soil-stored seed banks in fynbos tend to be concentrated in the upper 3–5 cm of the soil <br />What temperatures are reached under different conditions of biomass loads?<br />Labels with temperature sensitive paint. <br />Color changes permanently when exposed to heat for more than ten minutes<br />Sets placed at: Surface, 2 cm, 5 cm<br />
  22. 22. Results: Biomassburning<br />
  23. 23. Discussion: Biomassburning<br />Fuel load - temperature<br />Influence of depth<br />Highest temperature peaks <br />High temperatures more likely to happen in the surface. <br />
  24. 24. Experiments assisted:Revegetation<br /><ul><li>Identify species or guilds and densities which would effectively restore the ecological functions for invaded areas
  25. 25. 98 planting plots divided into two sub-plots: Burned and not burned
  26. 26. Treatments:
  27. 27. Control
  28. 28. High density planting
  29. 29. 9 plants/m²
  30. 30. Low density planting
  31. 31. 4 plants/m²
  32. 32. Seeding and planting
  33. 33. Eragostistef sowing</li></li></ul><li>Revegetation:Distribution of paired plots<br />
  34. 34. Revegetation with a mixture of native species selected by the R3G researchers under several considerations: <br />Species from surrounding, uninvaded reference sites<br />Species whose seeds could be collected, propagated and established well with relative ease:<br />Species that would grow quickly: this would potentially suppress alien recruitment.<br />Species that will provide good ground cover: This selection criteria considers the risk having bare ground exposed to erosion.<br />Revegetation:Criteria for species selection<br />
  35. 35. Revegetation:Conditions recommended for planting riparian vegetation in alien invaded fynbos<br />
  36. 36. Experiments performed:Management of seedbank<br />Comparison of two methods to eliminate unwanted biomass left after large scale <br /> Black Wattle clearing: <br />Burning<br />transformation to wood chips,<br />What happens to the seedbank?<br />From Black Wattle?<br />From the other species?<br />
  37. 37. Results: Management of seedbank<br />
  38. 38. Results: Effects of soil preparation methods on soil seedbank<br />
  39. 39. Results: Management of seedbank<br />Estimated germination means for Black Wattle and the other species group, separated by temperature range. <br />
  40. 40. Discussion: Management of seedbank<br />Germination of Black Wattle increased with the burned treatment <br />Control and wood chips treatment: almost no germination <br />Other species group, germination was observed but low in wood chips and control. <br />Not possible to define if germination in the controls section (sand control, wood chips control) was a result of the presence of seeds in the sand control or in the wood chips<br />Results dependant on:<br />the treatments<br />low seed rain<br />depletion of surface seedbank<br />not enough time for germination<br />Similar experiments: final results in 12 months<br />
  41. 41. Black Wattle: <br />Reduced presence of indigenous species in the study site<br />Decreased the quality of the riparian vegetation which was almost absent<br />Fell and Burn method, <br />Possible outbreak of Black Wattle with few indigenous species present<br />Conclusions<br />
  42. 42. Soil temperature: <br />Surface temperature<br />Large logs on wood stacks<br />Soil seedbank<br />Germination of Acacia mearnsii<br />Germination of other species<br />No separation between other species, did not allow to define groups of species, families or plant growth forms<br />Unclear which treatments influenced on the results obtained. <br />Time for experiments, was not enough<br />Conclusions<br />
  43. 43. ¡Muchas gracias!<br />