The effect of seed polymer coating technology to improve ecological restoration outcomes in Lowland Sand Fynbos

Thesis (MScConEcol)--Stellenbosch University, 2025.

Mbombo, B. 2025. The effect of seed polymer coating technology to improve ecological restoration outcomes in Lowland Sand Fynbos. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/24e2701a-8272-4664-af0c-19c7ae8a8110

ENGLISH ABSTRACT: The Lowland Sand Fynbos is a biodiversity-rich ecosystem important for conservation as it supports various plants endemic to the Cape Floristic Region of South Africa. Like many ecosystems worldwide, lowland fynbos, particularly Cape Flats Sand Fynbos confined to the City of Cape Town’s jurisdiction, is also experiencing high rates of degradation due to urbanisation. In addition to human encroachment and changing climate patterns, the land faces threats from invasion by alien species that hinder the successful restoration of this ecosystem. Restoration efforts – active restoration, by directing the sowing of seeds to counter the loss of vegetation components – and passive restoration, by removing alien species and allowing natural recovery, have resulted in suboptimal recovery of lowland fynbos vegetation. The unsuccessful seedling establishment of especially larger-seeded species in active sowing is potentially due to seed predation by rodents. Seed polymer coating technology presents a potential solution to overcome these challenges. This technology involves coating native seeds with materials that offer targeted treatments to the seeds to overcome ecological restoration barriers and enhance the success of restoration efforts. The coating materials consist of an active ingredient that will potentially benefit seedling emergence, improve germination, and protect seeds from biotic and abiotic challenges. This study’s aim was two-fold: (1) to investigate the effect of seed-coating materials on the germination and seedling emergence of eight fynbos species of contrasting families, and (2) to investigate the effect of chili flake-coated seeds on rodent seed removal/predation. The findings suggested that seed polymer coating technology can improve the ecological restoration of Lowland Sand Fynbos and confirm that fynbos seeds still need to be pretreated with either heat or smoke treatment to break their dormant state before applying coating materials. In the findings of polymer coating technology on the effect of different coating materials (ash, chili flakes, smoke water and hydrogel) on seeds that have been exposed to smoke and heat treatment, significant differences of coating materials were observed in five species compared to the control. In only three out of the five species, coating materials significantly increased the number of germinated seeds compared to the control. The highest germination percentage of coated seeds was observed in Anthospermum aethiopicum species coated with either smoke water or ash coating materials. A. aethiopicum germinated to a maximum of 92% and 74% once coated with smoke water and ash, respectively, which was significantly higher than the control treatment (19%). While Trichocephalus stipularis and Thamnochortus punctatus need to be coated with smoke water and chili flakes or hydrogel for optimal germination, respectively. The highest germination inhibition was observed in coating materials of either ash, smoke water, hydrogel or chili flakes on Passerina corymbosa, Pelargonium capitatum and T. punctatus seeds, all with 0% germination percentages. While the control treatments resulted in germination percentages of 17%, 17% and 4%, respectively. Seedling emergence inhibition in the nursery was only observed in coating materials of smoke water (0%) and chili flakes (0%) on A. aethiopicum, as well as with chili flakes (0%) and ash (0%) coating materials on P. corymbosa seeds, compared to the control (2% and 0%, respectively). Furthermore, the combination of the best coating materials tested for each species, combined with either or both chili flakes and hydrogel materials, showed positive effects, whereas other combinations showed insignificant differences to the control within the species. The best coating material combination results demonstrated increased percentages of germinated seeds and seedling emergence in all species tested except for P. capitatum, which significantly reduced the number of germinated seeds and seedlings compared to those seeds treated with 100% smoke water (47%) as they germinated less than the control (17%), while their highest germination emergence was 22% in the tested coating material combinations. These findings provide useful insights that can improve active restoration efforts in Lowland Sand Fynbos ecosystems in the field. The effect of chili flake coating material as a predator repellent on fynbos seeds confirmed that predator repellents containing capsaicin as an active ingredient deter seed removal by granivorous rodents. In addition, factors such as seed size, whether small or large, can influence the number of seeds removed by rodents, on both chili flake-coated seeds and uncoated seeds, thus highlighting the importance of understanding rodent preferences in this lowland ecosystem. In conclusion, the study offers useful insights into optimising seed polymer coating technology for ecological restoration of Lowland Sand Fynbos and understanding the impacts of coating materials and their application method on germination, seedling emergence and protection from granivores, potentially contributing to improved active sowing restoration strategies.

AFRIKAANSE OPSOMMING: Laaglandsand-fynbos is 'n biodiversiteitryke ekosisteem wat belangrik is vir bewaring aangesien dit verskeie plante endemies aan die Kaapse Floristiese Streek van Suid-Afrika ondersteun. Soos baie ekosisteme wêreldwyd, ervaar laagland-fynbos, veral Kaapse Vlakte Sand Fynbos beperk tot die Stad Kaapstad se jurisdiksie, ook hoë koerse van agteruitgang as gevolg van verstedeliking. Benewens menslike indringing en veranderende klimaatspatrone staar die land bedreigings in die gesig van indringing deur uitheemse spesies wat die suksesvolle herstel van hierdie ekosisteem belemmer. Herstelpogings – aktiewe herstel, deur die saai van saad uit te voer om die verlies van plantegroeikomponente teen te werk – en passiewe herstel, deur uitheemse spesies te verwyder en natuurlike herstel toe te laat, het gelei tot suboptimale herstel van fynbosplantegroei in die laagland. Die onsuksesvolle saailingvestiging van veral grotersaadspesies in aktiewe saai is moontlik te wyte aan saadpredasie deur knaagdiere. Saadpolimeerbedekkingstegnologie bied 'n potensiële oplossing om hierdie uitdagings te oorkom. Hierdie tegnologie behels die bedekking van inheemse sade met materiale wat doelgerigte behandelings aan die sade bied om ekologiese herstelversperrings te oorkom en die sukses van herstelpogings te verbeter. Die deklaagmateriaal bestaan uit 'n aktiewe bestanddeel wat moontlik die opkoms van saailinge sal bevoordeel, ontkieming sal verbeter en sade teen biotiese en abiotiese uitdagings sal beskerm. Die doel van hierdie studie was tweeledig: (1) om die effek van saadbedekkingsmateriaal op die ontkieming en saailingopkoms van agt fynbosspesies van kontrasterende families te ondersoek, en (2) om die effek van brandrissievlokkiebedekte sade op knaagdiersaadverwydering/predasie te ondersoek. Die bevindinge het voorgestel dat saadpolimeerbedekkingstegnologie die ekologiese herstel van Laaglandsand-fynbos kan verbeter en bevestig dat fynbossade nog voorbehandel moet word met óf hitte- óf rookbehandeling om hul dormante toestand te verbreek voordat bedekkingsmateriaal toegedien word. In die bevindinge van polimeerbedekkingstegnologie oor die effek van verskillende bedekkingsmateriale (as, brandrissievlokkies, rookwater en hidrogel) op sade wat aan rook- en hittebehandeling blootgestel is, is beduidende verskille van bedekkingsmateriaal in vyf spesies waargeneem in vergelyking met die kontrole. In slegs drie uit die vyf spesies het bedekkingsmateriaal die aantal ontkiemde sade aansienlik verhoog in vergelyking met die kontrole. Die hoogste ontkiemingspersentasie van bedekte sade is waargeneem in Anthospermum aethiopicum spesies bedek met óf rookwater óf asbedekkingsmateriaal. A. aethiopicum het tot 'n maksimum van 92% en 74% ontkiem sodra dit onderskeidelik met rookwater en as bedek is, wat aansienlik hoër was as die kontrolebehandeling (19%). Trichocephalus stipularis en Thamnochortus punctatus moet egter onderskeidelik met rookwater en rissievlokkies of hidrogel bedek word vir optimale ontkieming. Die hoogste ontkiemingsinhibisie is waargeneem in bedekkingsmateriaal van óf as, rookwater, hidrogel óf rissievlokkies op Passerina corymbosa-, Pelargonium capitatum- en T. punctatus-sade, almal met 0% ontkiemingspersentasies; terwyl die kontrolebehandelings op ontkiemingspersentasies van onderskeidelik 17%, 17% en 4% gelei het. Saailing-opkomsinhibisie in die kwekery is slegs waargeneem in deklaagmateriaal van rookwater (0%) en brandrissievlokkies (0%) op A. aethiopicum, asook met brandrissievlokkies (0%) en as (0%) deklaagmateriaal op P. corymbosa-sade, vergeleke met die kontrole (2% en 0%, onderskeidelik). Verder het die kombinasie van die beste bedekkingsmateriale wat vir elke spesie getoets is, gekombineer met een of beide brandrissievlokkies en hidrogelmateriale, positiewe effekte getoon, terwyl ander kombinasies onbeduidende verskille tot die beheer binne die spesie getoon het. Die beste bedekkingsmateriaalkombinasieresultate het verhoogde persentasies ontkiemde sade en saailinge- opkoms getoon in alle spesies wat getoets is, behalwe vir P. capitatum, wat die aantal ontkiemde sade en saailinge aansienlik verminder het in vergelyking met die sade wat met 100% rookwater (47%) behandel is, aangesien hulle minder ontkiem het as die kontrole (17%), terwyl hul hoogste ontkiemingskombinasie 22% was. Hierdie bevindinge verskaf nuttige insigte wat aktiewe herstelpogings in Laaglandsand-fynbos-ekosisteme in die veld kan verbeter. Die effek van brandrissievlokkieslaagmateriaal as 'n roofdierafweermiddel op fynbossade het bevestig dat roofdierafweermiddels wat capsaïsien bevat as 'n aktiewe bestanddeel saadverwydering deur graanetende knaagdiere afskrik. Daarbenewens kan faktore soos saadgrootte, hetsy klein of groot, die aantal sade wat deur knaagdiere verwyder word, op beide brandrissievlokkiebedekte sade en onbedekte sade beïnvloed, en sodoende die belangrikheid beklemtoon om knaagdiervoorkeure in hierdie laagland-ekosisteem te verstaan. Ten slotte bied die studie nuttige insigte in die optimalisering van saadpolimeerbedekkingstegnologie vir die ekologiese herstel van Laaglandsand-fynbos en die begrip van die impak van bedekkingsmateriale en hul toedieningsmetode op ontkieming, saailingopkoms en beskerming teen granivore, wat moontlik tot verbeterde aktiewe saaiherstelstrategieë bydra.

Masters