Loading...
Overcoming desiccation in an African cycad genus: adaptive approaches for improving recruitment in Encephalartos
Author(s)
Ngaka, Ngawethu
Date Issued
2024
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
Cycad populations in the wild are declining due to human pressures, and recovery efforts are
constrained by the high mortality of seeds and seedlings, particularly as a result of desiccation.
Desiccation reduces seed survival and thus seedling recruitment in the wild. This limits the
viability of cycad populations in the wild. Therefore, this study involved testing different
substrates designed to retain moisture and thus improve cycad seed survival and juvenile
establishment in the wild. It was hypothesized that the addition of water-retaining compounds,
such as Coir and Hydrogel, into the growing medium would improve moisture availability and
increase seed and juvenile establishment and survival under drought conditions. To test the
hypothesis, experimental treatments comprising four substrates and three watering regimes,
representing no drought, moderate drought and prolonged drought, were tested in a greenhouse
to evaluate their effects on cycad establishment and survival. Chapter two of this thesis
investigates the effects of these treatments on growth from seeds for Encephalartos altensteinii,
with an additional test to determine the effect of sowing depth on seedling emergence and
survival. Chapter three tested the effectiveness of the treatments on translocated juvenile plants
(8 years old) of Encephalartos altensteinii. The results proved that Coir and Hydrogel
significantly enhanced substrates moisture content used for growing cycad seeds and juveniles.
Seedling development and survival was also significantly influenced by substrates, watering
regimes, and sowing depth, as seeds sown 3cm deep had higher seedling survival than at the
surface within all the substrates except in Coir. However, for the cycad juveniles, neither
substrates or watering treatments significantly influenced survival. Hydrogel and Coir proved
to enhance moisture retention which subsequently improving seedling establishment and
survival, thus provides key information for cycad restoration protocols. This study further
impactfully contributes to the conservation of threatened cycads by providing new knowledge
that could be essential to maximize moisture availability and thus improve the establishment
and survival of cycad seeds and juveniles in the wild.
constrained by the high mortality of seeds and seedlings, particularly as a result of desiccation.
Desiccation reduces seed survival and thus seedling recruitment in the wild. This limits the
viability of cycad populations in the wild. Therefore, this study involved testing different
substrates designed to retain moisture and thus improve cycad seed survival and juvenile
establishment in the wild. It was hypothesized that the addition of water-retaining compounds,
such as Coir and Hydrogel, into the growing medium would improve moisture availability and
increase seed and juvenile establishment and survival under drought conditions. To test the
hypothesis, experimental treatments comprising four substrates and three watering regimes,
representing no drought, moderate drought and prolonged drought, were tested in a greenhouse
to evaluate their effects on cycad establishment and survival. Chapter two of this thesis
investigates the effects of these treatments on growth from seeds for Encephalartos altensteinii,
with an additional test to determine the effect of sowing depth on seedling emergence and
survival. Chapter three tested the effectiveness of the treatments on translocated juvenile plants
(8 years old) of Encephalartos altensteinii. The results proved that Coir and Hydrogel
significantly enhanced substrates moisture content used for growing cycad seeds and juveniles.
Seedling development and survival was also significantly influenced by substrates, watering
regimes, and sowing depth, as seeds sown 3cm deep had higher seedling survival than at the
surface within all the substrates except in Coir. However, for the cycad juveniles, neither
substrates or watering treatments significantly influenced survival. Hydrogel and Coir proved
to enhance moisture retention which subsequently improving seedling establishment and
survival, thus provides key information for cycad restoration protocols. This study further
impactfully contributes to the conservation of threatened cycads by providing new knowledge
that could be essential to maximize moisture availability and thus improve the establishment
and survival of cycad seeds and juveniles in the wild.
Additional information
Thesis (Master of Conservation Science)--Cape Peninsula University of Technology, 2024
File(s)![Thumbnail Image]()
Loading...
Name
Ngaka_N_ 214113833.pdf
Size
1.47 MB
Format
Adobe PDF
Checksum
(MD5):c3b49fe253f1cd3e400e60987e1c0b85
Sponsor(s)
South African National Biodiversity Institute (SANBI)