Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Exploring the concept of applied nucleation as a restoration tool in a previously invaded Mediterranean climate vegetation type

Auteur : Lehman, Tevan William Key

Université de soutenance : Stellenbosch University

Grade : Master of Science (MScConsEcol ) 2022

Résumé partiel
There is a need to scale-up ecological restoration efforts. The urgency to restore degraded habitats means that we, as researchers, need to be at the forefront of new and innovative restoration techniques. Sometimes this means assessing the efficacy of techniques which are not commonly employed in the vegetation type in need of restoration. In the case of this study, it involved exploring the concept of applied nucleation as a restoration tool in Cape Flats Sand Fynbos (CFSF). Applied nucleation involves establishing clusters of vegetation (nuclei) either by sowing or planting, and these clusters then produce and set seed into the surrounding area, facilitating nucleation. Colonization is further facilitated when the clusters of vegetation establish and are able to capture seed from other species (Corbin & Holl, 2012). This thesis assessed whether applied nucleation would be an effective restoration method in a vegetation type where it has not been employed before. This was done by resurveying previously restored plots to assess whether sown species had begun to set seed and nucleate into the surrounding environment (Chapter 2), and by designing a simulation model to assess which invasion management regimes and Cape Flats Sand Fynbos Species would most effectively facilitate nucleation (Chapter 3). The management regimes were fell & stack whereby felled Acacia biomass was stacked into brushpiles and fell & burn involved burning the felled Acacia biomass. A resurvey of active restoration plots established in 2013 through sowing indigenous Cape Flats Sand Fynbos investigated which species had established and persisted, as well as determined which species had set seed outside the initial 10m x 5m sowed plot. Fourteen plots were resurveyed in 2019 by determining species presence and abundance. This information was then compared to survey data from 2014 and 2017 to assess how the restored plots were faring. Of the 30 species sown in 2013, only 11 were observed to still be persisting in 2019. By establishing a larger 20m x 20m plot around the initial sowing plot, young plants of the species inside in sowing plot were identified, and these species were assumed to be nucleating species. The size (volume) of these young plants as well as their distance to the sowing plot was measured. This was to determine whether there was a significant difference between plant size inside the plot as opposed to outside, as well as to determine the distribution of plants of different ages. Plant size was used as a surrogate for plant age. Four species were seen to have consistently set seed outside the initial sowing plots, and these were Anthospermum aethiopicum, Ifloga repens, Dimorphotheca pluvialis, and Pelargonium capitatum.

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