Restoration of Cape Flats Sand Fynbos : the significance of pre-germination treatments and moisture regime
Mukundamago, Mukundi (2016-03)
ENGLISH ABSTRACT: The seed ecology of the Cape Flats Sand Fynbos (CFSF) vegetation’s species in Blaauwberg Nature Reserve, in Western Cape South Africa, was investigated within the context of a broader restoration ecology project “Blaauwberg Ecological Restoration Project”1.
Cape Flats Sand Fynbos (CFSF) vegetation is considered as a critically endangered vegetation type due to agricultural development, urban transformation, and degradation caused by invasive alien Acacia species. The City of Cape Town is clearing alien plants at Blaauwberg Nature Reserve (BBNR) in an attempt to restore this remaining CFSF fragment. These efforts are associated with challenges, since alien stands have depleted indigenous soil-stored seedbanks. The premise for this seed ecology study was that restoration of degraded CFSF is possible through applied management programmes based on the methodology and practice of active restoration. Active restoration is necessary in order to establish the major indigenous plant guilds and to revive areas that have been degraded due to the effects of the alien plants. Pre-germination treatments including smoke-derived compounds have been known to promote seed germination; however, after a burn in Blaauwberg Nature Reserve, seeds sown in the field had low germination. One reason for the low germination of re-introduced indigenous species could be a lack of pre-germination treatments prior to sowing or drought thereof.
The research on the implementation of seed ecology study was carried out in anticipation of three major outcomes. First, to determine pre-germination treatments that can improve germinability of seeds of selected indigenous target species to be used in large-scale restoration projects. Second, to assess the value of smoke as a germination cue for indigenous CFSF species; more specifically, it focuses on the germination of indigenous species following different smoke treatments. Lastly, to assess soil moisture as a potential limiting factor for seed germination and seedling establishment in lowland sand fynbos. In general, the research investigated the effect of desiccation on seed emergence and the survival of seedlings.
Seed and soil collections were performed in Blaauwberg Nature Reserve, Western Cape, South Africa and in natural vegetation remnants along the N7 between July 2012 and January 2013. Seeds were collected, cleaned, sorted, and then stored. The main plant guilds that were selected are, Restioids, Ericoids, Proteoids, annual forbs and geophytes. Portions of seeds were set aside for different experiments (i.e. pre-germination treatments, viability test, smoke test and desiccation test). The results of the first study of viability test, germination rate, and germination period were analysed. Species showed varying responses to the different treatments with only the smoke water treatment having a consistent positive effect on seed germination for all functional groups. Only the annual, Senecio elegans, had a negative response to smoke water pre-germination treatment. A positive response was observed in Thamnochortus punctatus and Erica plumosa with the application of combination of smoke water and heat. Another positive response was noticed in Babiana villosula with the application of scarification pre-germination treatment. Additional analyses of germination period, germination lag phase and duration showed the same pattern as germinability wherein species had significant differences in germinability when there was no significant differences on germination period and vice versa.
A comparison of different viability tests (i.e. x-ray, tetrazolium and cut test) indicated that the cut test is more efficient in determining viability. Nonetheless, it is recommended to collect seeds when they are naturally dispersing since cut test is not practical in the field wherein small seeds are collected. Pre-germination treatments should be applied on target species in all restoration applications to maximise germinability and establishment. The study shows that although pre-germination treatment responses are species-specific smoke water pre-germination treatment could be used for all functional groups. Other treatments can be applied for specific species.
The second study showed that plant-derived smoke had the ability to enhance seed germination of a number of plant species. Plant-derived smoke enhancement was species-specific. Some species’ germination increased significantly with pre-smoked seeds only, whereas others’ germination increased significantly with pre-smoked soil only and some other species germination increased significantly with a combination of pre-smoked soil and seeds. Based on these observations, it is recommended that seeds be pre-smoked before sowing in the field, especially in the absence of a prescribed burn.
The third study focused on selected Cape Flats Sand Fynbos species that were tested for desiccation tolerance of both germinants and seedlings. I ran experiments in controlled growth chambers in parallel with desiccation tolerance investigation of seedlings of the target species in a greenhouse experiment. Results showed that almost all species germinated and they were all tolerant to desiccation.
The results within the scope of this study will help shed some light on and further enhance existing active practical restoration efforts in Cape Flats Sand Fynbos. In order for such efforts to be effective, it is important to use appropriate pre-germination treatments to enhance germination. More importantly, it should be noted that drought or desiccation are unlikely causes of poor germination/ establishment. It is probable that enhanced nutrient levels or a change in the soil microbial community might be the reason for a lack of germination/establishment in the field.
Amidst the observations made and the conclusions arrived at, it is recommended that further research should be conducted in the greenhouse alongside a field experiment to compare germination of Acacia saligna and indigenous CFSF species. This is because in the nursery trial, you can control some of the environmental variables such as soil nutrients and moisture and be able to investigate these factors on germination under soil conditions and the field experiment will have a variety of environmental factors involved.
AFRIKAANSE OPSOMMING: Die saadekologie van die Kaapse Vlakte-sandfynbos (CFSF) plantegroei spesies in Blaauwberg Natuurreservaat, in die Wes-Kaap Suid-Afrika, is ondersoek binne die konteks van 'n breër restourasie-ekologie projek "Blaauwberg Ekologiese Restourasie Projek".2
Kaapse Vlakte-sandfynbos (CFSF) plantegroei word beskou as 'n krities bedreigde plantegroei tipe weens landbou-ontwikkeling, stedelike transformasie, en agteruitgang veroorsaak deur uitheemse Acacia spesies. Die Stad Kaapstad haal uitheemse plante uit in Blaauwberg Natuurreservaat (BBNR) in 'n poging om hierdie oorblywende CFSF fragment te herstel. Hierdie pogings gaan gepaard met uitdagings, aangesien uitheemse plotte inheemse grond gestoorde saadbanke uitgeput het. Die uitgangspunt vir hierdie saadekologie studie was dat die herstel van gedegradeerde CFSF moontlik is deur toegepaste bestuursprogramme gebaseer op die metode en praktyk van aktiewe herstel. Aktiewe herstel is nodig om die groot inheemse plant gildes te vestig en gebiede wat ontaard het weens die gevolge van die indringerplante te laat herleef. Voor-ontkiemingsbehandelings waaronder rook-afkomstige samestellings is bekend daarvoor om ontkieming te bevorder; maar na 'n brand in Blaauwberg Natuurreservaat, het sade gesaai in die veld lae ontkieming getoon. Een rede vir die lae ontkieming van her-bekendgestelde inheemse spesies kan wees as gevolg van 'n gebrek aan voor-ontkiemingsbehandelings, voor die saai of droog daarvan.
Die navorsing oor die implementering van die saadekologie studie is uitgevoer as gevolg van die afwagting van drie groot uitkomste. Eerstens, om voor-ontkieming behandelings te bepaal wat ontkiemingsvermoë van sade van gekose inheemse teiken spesies, wat gebruik sal word in grootskaalse herstel projekte, te kan verbeter. Tweedens, om die waarde van rook as 'n ontkiemingsteken vir inheemse CFSF spesies te evalueer; meer spesifiek, dit fokus op die ontkieming van inheemse spesies na verskillende rook behandelings. Laastens, om grondvog te evalueer as 'n potensiële beperkende faktor vir saadontkieming en saailingvestiging in laagland sand fynbos. In die algemeen het die navorsing die effek van uitdroging op saad opkoms en die oorlewing van saailinge ondersoek.Saad- en grondinsamelings is gedoen in Blaauwberg Natuurreservaat, Weskaap, Suid-Afrika en in natuurlike plantegroei oorblyfsels langs die N7 tussen Julie 2012 en Januarie 2013. Saad is versamel, skoongemaak, gesorteer en dan gestoor. Die belangrikste plant gildes wat gekies is, is Restioids, Ericoids, Proteoids, eenjarige kruidagtige-plante en geofiete. Gedeeltes van die sade is opsy gesit vir verskillende eksperimente (d.w.s. voor-ontkiemingsbehandelings, lewensvatbaarheidtoets, rooktoets en uitdrogingstoets). Die resultate van die eerste studie van die lewensvatbaarheidstoets, ontkiemingstempo en ontkiemingstydperk is ontleed. Spesies het uiteenlopende reaksies op die verskillende behandelings getoon, met net die rookwater behandeling wat 'n volgehoue positiewe effek op ontkieming vir alle funksionele groepe gehad het. Slegs die eenjarige, Senecio elegans, het 'n negatiewe reaksie op rookwater voor-ontkiemingsbehandeling getoon . 'n Positiewe reaksie is waargeneem in Thamnochortus punctatus en Erica plumosa met die toepassing van 'n kombinasie van rookwater en hitte. Nog 'n positiewe reaksie is opgemerk in Babiana villosula met die toepassing van insnydings in die vel as voor-ontkiemingsbehandeling. Addisionele ontledings van ontkiemingstydperk, ontkiemings-wagperiode en duur het dieselfde patroon as ontkiemingsvermoë getoon, waarin spesies beduidende verskille in ontkiemingsvermoë gehad en daar geen beduidende verskille in ontkiemingstydperk was en omgekeerd.
'n Vergelyking van verskillende lewensvatbaarheidstoetse (d.w.s. x-strale, tetrazolium en die snytoets) het aangedui dat die snytoets meer doeltreffend is in die bepaling van lewensvatbaarheid. Nietemin word dit aanbeveel om saad in te samel wanneer hulle natuurlik versprei, aangesien die snytoets nie prakties in die veld is nie, wanneer klein sade versamel word. Voor-ontkiemingsbehandelings moet toegepas word op teiken spesies in alle herstel toepassings om ontkiemingsvermoë en vestiging te maksimeer. Die studie toon dat hoewel voor-ontkiemingsbehandeling reaksies spesie-spesifiek is, rookwater voor-ontkiemingsbehandeling gebruik kan word vir alle funksionele groepe. Ander behandelings kan toegepas word vir spesifieke spesies.
Die tweede studie het getoon dat plant-afkomstige rook die vermoë het om die ontkieming van 'n aantal plantspesies te bevoordeel. Plant-afkomstige rook bevoordeling was spesie-spesifiek. Sommige spesies se ontkieming het aansienlik toegeneem met slegs voor-gerookte sade, terwyl ander se ontkieming aansienlik toegeneem het met slegs voor-gerookte grond en 'n paar ander spesies se ontkieming het aansienlik toegeneem met 'n kombinasie van die voor-gerookte grond en sade. Op grond van hierdie waarnemings word dit aanbeveel dat sade vooraf gerook word, voor dit in die veld gesaai word, veral in die afwesigheid van 'n voorgeskrewe brand.
Die derde studie het gefokus op uitgesoekte Kaapse Vlakte-sandfynbos spesies wat getoets is vir uitdroogtoleransie in beide spruite en saailinge. Ek het eksperimente uitgevoer in beheerde groeikaste in parallel met uitdroogtoleransie ondersoeke van saailinge van die teiken spesies in 'n kweekhuis eksperiment. Resultate het getoon dat byna al die spesies ontkiem het en hulle was almal verdraagsaam teen uitdroging.
Die resultate binne die bestek van hierdie studie sal help lig werp op en verder die bestaande aktiewe praktiese herstel pogings in Kaapse Vlakte-sandfynbos verbeter. Ten einde vir sulke pogings om doeltreffend te wees, is dit belangrik om toepaslike voor-ontkiemingsbehandelings te gebruik om ontkieming te verbeter. Meer belangrik, moet daarop gelet word dat droogte of uitdroging onwaarskynlike oorsake van swak ontkieming/vestiging is. Dit is hoogs waarskynlik dat verhoogde voedingstofvlakke of 'n verandering in die grond mikrobiese gemeenskap die rede vir 'n gebrek aan ontkieming/vestiging in die veld kan wees.
Te midde van die waarnemings en die gevolgtrekkings, dink ek verdere navorsing moet gedoen word in die kweekhuis tesame met veld eksperimente, met vergelyking van waterverhoudings en voedingstofverdraagsaamheid tussen Acacia saligna en inheemse CFSF spesies. Dit is omrede jy in die kwekery 'n paar van die omgewingsveranderlikes kan beheer soos grondvoedingstowwe en vog en in staat is om hierdie faktore op ontkieming onder grondtoestande te ondersoek.
Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98424