Potential of soil seed bank and ungulate-mediated endozoochory in old field restoration:
- Authors: Ruwanza, Sheunesu
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150216 , vital:38950 , https://0-muse.jhu.edu.wam.seals.ac.za/article/750319/pdf
- Description: Soil seed bank plays a key role in old field restoration because it provides information about plant species that may regenerate (Hopfensperger 2007). Most studies on old field restoration have concentrated on floristic similarities between soil seed bank and standing vegetation (Török et al. 2018). However, investigating the effects of proximity to natural/old field edge (habitat fragmentation border) on soil seed bank could yield better recovery predictions. Proximity to natural/old field edge may favour recruitment of a different plant community than that found in the old field interior. This due to favorable abiotic (e.g., soil moisture) and biotic (e.g., seed dispersal) microenvironments created near the edge. On the other hand, ungulate-mediated endozoochory has been shown to potentially facilitate ecological restoration in degraded systems, given that ungulates disperse diaspores across different landscapes (Baltzinger et al. 2019). However, ungulate-mediated endozoochory dispersal in degraded old fields is affected by several factors that include availability of nearby natural perches that attract dispersers, structural vegetation complexities, presence of food especially fruits, and feeding regimes (Baltzinger et al. 2019).
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Topsoil transfer from natural renosterveld to degraded old fields facilitates native vegetation recovery:
- Authors: Ruwanza, Sheunesu
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148639 , vital:38758 , https://doi.org/10.3390/su12093833
- Description: The transfer of soils from intact vegetation communities to degraded ecosystems is seen as a promising restoration tool aimed at facilitating vegetation recovery. This study examined how topsoil transfer from intact renosterveld to degraded old fields improves vegetation diversity, cover, and composition. Transferred topsoil were overlaid on 30 quadrats, each measuring 1 m2, in May 2009. Eight years following the initial soil transfer, vegetation diversity in the soil transfer site showed an increase towards the natural site compared to the old field site where no soil transfer was administered. Both species richness and cover for trees and shrubs in the soil transfer site increased towards the natural site, though this was not the case for herbs and grasses. One-way analysis of similarity (ANOSIM) showed significant (R = 0.55) separation in community composition between sites. The study concludes that soil transfer from intact renosterveld to degraded old fields is a promising restoration technique because it increases species diversity and cover and facilitates vegetation recovery. A significant restoration implication of this study is that soil transfer introduces key renosterveld native tree and shrub species that can facilitate successful restoration and act as restoration foci or nurse plants.
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Aspect and slope as determinants of vegetation composition and soil properties in coastal forest backdunes of Eastern Cape, South Africa
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180376 , vital:43358 , xlink:href="https://doi.org/10.1111/aje.12343"
- Description: Coastal sand dune ecosystems are subjected to many stress and disturbance factors that are particularly high in the foredunes compared to the backdunes. Although a few studies have been conducted on eastern coastline sand dunes of South Africa, none have examined the relationship between aspect and slope on vegetation composition and soil properties of coastal forest backdunes. Vegetation and soil sampling were conducted in 11 transects, each with four plots measuring 10 × 10 m, located on the seaward and landward sides and on middle and lower slopes of backdunes of Bathurst coastal forest. A total of 39 species were identified, of which 23 were trees and shrubs, thirteen were forbs and three were grasses. The data show that both aspect and slope had limited influence on vegetation community assemblage and soil properties, but had significant effects on individual species distribution. There was a grass-dominated community on the middle slope and a tree- and shrub- dominated community on the lower slope. These two plant communities act as the required coastal forest ecosystem engineer driving variability in soil properties between the slopes, the most prominent being high soil nutrients and moisture in the lower slopes compared to the middle slopes.
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Ecosystem-scale impacts of non-timber forest product harvesting: Effects on soil nutrients
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180099 , vital:43309 , xlink:href="https://doi.org/10.1111/1365-2664.12891"
- Description: The harvesting of non-timber forest products (NTFPs) is a global phenomenon, the sustainability of which has been studied for many species at the individual and population level. However, the broader scale impacts of NTFP harvesting have been acknowledged but rarely examined. We assessed plant size and the soil attributes undercanopy and in the open, in replicate, paired harvested and non-harvested sites for three NTFPs differing in the extent of biomass removed, i.e. timber for firewood from a tree (Acacia karroo), fruits from a cactus (Opunita ficus-indica) and flowering culms from a grass (Cymbopogon marginatus). Soil variables tested included pH, resistivity, P, total N, nitrate nitrogen, ammonium nitrogen, K, Na, Ca and Mg. The extent of loss of soil nutrients decreased across the three NTFPs relative to the proportion of biomass removed. Thus, significant differences in more soil variables were evident for the firewood species, least for the fruit species and intermediate for the grass species. Lower soil pH, P, C and K were evident in soils collected underneath A. karroo, while losses in cations of Na, Ca and Mg were reported in soils underneath C. marginatus, and only NO3N losses were recorded underneath O. ficus-indica. Our study reveals that while non-timber forest product (NTFP) harvesting may affect soil nutrients, this is not uniform between species and is likely to be a function of the extent of biomass removed and harvesting frequency. This indicates the need for caution in generalisations about the ecosystem-level impacts of NTFP harvesting as well as a concerted effort to better understand impacts at a greater range of scales than has been the case to date.
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The effects of expansive shrubs on plant species richness and soils in semi-arid communal lands, South Africa
- Authors: Sholto-Douglas, Craig , Shackleton, Charlie M , Ruwanza, Sheunesu , Dold, Tony
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398394 , vital:69408 , xlink:href="https://doi.org/10.1002/ldr.2745"
- Description: Expansion by expansive species can have severe ecological, social and economic impacts through the reduction of ecosystem goods and services and species richness. However, expansion by expansive species may also offer benefits to ecosystems and humans, through the supply of ecosystem goods and services (such as firewood, fodder and fruits), as well as potentially offering refugia in heavily used landscapes. Here, we examine the effects of four expansive dwarf shrub species (Aspalathus subtingens, Dicerothamnus rhinocerotis, Pteronia incana and Oedera genistifolia) on plant species richness (at the point scale), vegetation cover, soil properties and whether the expansive species offer refugia to other species. Plant species richness, cover and soil properties were recorded in 1-m2 quadrats located within a mosaic of expanded and non-expanded patches for the four expansive shrub species. Plant species richness was significantly higher in the non-expanded areas compared to the expanded ones for all four expansive species. Some of the expansive shrubs provided refugia to certain plant species and limited the frequency of other species. With regard to species composition, there was little separation of expanded and non-expanded samples within sites, indicating that the site factors were stronger determinants of plant species richness and composition than expansion. Therefore, it is more likely that the reduction in species richness in expanded sites is caused by multiple drivers, including vegetation attributes cover, litter cover and soil nutrients (organic C, Zn and P) and soil compaction.
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Allelopathic effects of Lantana camara on indigenous forest species in South Africa
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182296 , vital:43818 , xlink:href="http://www.allelopathyjournal.org/?"
- Description: Lantana camara, is an invasive plant in South Africa and greatly influences the forest spp. In greenhouse, we evaluated the allelopathic effects of aqueous extracts of L. camara leaf, stem and root on 5-test species, (3-forest species viz., Acacia natalitia, Kiggalaria africana and Searsia crenata and 2-crops: Solanum lycopersicum and Lactuca sativa). Potential allelopathic compounds present in L. camara leaf, stem and root aqueous extracts were identified using gas chromatography mass spectrometry (GC-MS). The leaf, stem and root aqueous extracts of L. camara reduced the seed germination and seedling growth of all test species showing that L. camara aqueous extracts were deleterious to all test species. We identified 92 major volatile organic components in L. camara aqueous extracts. These compounds had the potential to inhibit the germination and seedling growth of test crops. The leaf, stem and root aqueous extracts of L. camara contained the allelopathic compounds that inhibited the germination and seedling growth of indigenous forest species and crop species.
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Effects of the invasive shrub, Lantana camara, on soil properties in the Eastern Cape, South Africa
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180459 , vital:43391 , xlink:href="https://doi.org/10.1111/wbm.12094"
- Description: Lantana camara L. is an invasive alien shrub of worldwide significance due to its impacts on biodiversity. It can alter the soil properties of invaded ecosystems and, as a result, affect management outcomes. However, knowledge on the impacts of L. camara on soil properties is scanty, especially in South Africa, despite the pervasive presence of the plant in the country. In this comparative study, the soils underneath L. camara were assessed in order to determine if they had different properties (soil physico-chemical properties, penetration resistance, infiltration, hydraulic conductivity and water repellency) in comparison to the soils in adjacent natural sites in the Eastern Cape, South Africa. Soil samples were collected from the top soil beneath the canopy of both L. camara-invaded and adjacent natural sites in five different locations over three summer months. The soils that were collected from underneath L. camara had a significantly higher total C, total P, gravimetric soil moisture (in November and December) and were repellent, compared to the soils in the adjacent natural sites. Soil penetration resistance was significantly higher in the natural sites than in the L. camara-invaded sites. The soil hydraulic conductivity, soil infiltration rate, soil pH, exchangeable cations and total N showed no significant difference between the invaded and the natural sites. It appears that the soils underneath L. camara have a high total C and total P, soil moisture and are repellent, thus influencing nutrient cycling, potentially making the soil properties underneath it ideal for its own growth. This could contribute to the success of L. camara as an invasive species.
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Incorporation of environmental issues in South Africa’s municipal Integrated Development Plans
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180481 , vital:43393 , xlink:href="https://doi.org/10.1080/13504509.2015.1062161"
- Description: The transition to full democracy in South Africa in 1994 saw local government becoming the focal point for dealing with socio-economic development needs of communities. The Integrated Development Plan (IDP) has been used as the tool for guiding local development objectives, balanced against environmental demands within a sustainable development paradigm. Here we examine the extent to which this is being achieved through an analysis of IDPs from 35 different municipalities at three scales. We test the hypothesis that the metropolitan municipalities are better at mainstreaming environmental issues into their IDPs than local and district municipalities. Results indicate that mainstreaming environmental issues in IDPs is still low. The hypothesis that metropoles are better at mainstreaming environmental issues than district and local municipalities was not accepted since there were no significant differences between municipalities. There was low relative budget allocations and inclusion of vision and mission statements that mainstream environmental issues in all municipalities. For mainstreaming of environmental issues to be effective in IDPs, both proactive approaches and multi-faceted bottom-up and top-down approaches are suggested.
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Unpacking Pandora’s box: Understanding and categorising ecosystem disservices for environmental management and human wellbeing
- Authors: Shackleton, Charlie M , Ruwanza, Sheunesu , Sinasson Sanni, Gisele , Bennett, S , De Lacy, Peter , Modipa, Rebone D , Mtati, Nosiseko , Sachikonye, Mwazvita T B , Thondhlana, Gladman
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182113 , vital:43801 , xlink:href="https://doi.org/10.1007/s10021-015-9952-z"
- Description: Research into the benefits that ecosystems contribute to human wellbeing has multiplied over the last few years following from the seminal contributions of the international Millennium Ecosystem Assessment. In comparison, the fact that some ecosystem goods and services undermine or harm human wellbeing has been seriously overlooked. These negative impacts have become known as ecosystem disservices. The neglect of ecosystem disservices is problematic because investments into the management or reduction of ecosystem disservices may yield better outcomes for human wellbeing, or at a lower investment, than management of ecosystem services. Additionally, management to optimise specific ecosystem services may simultaneously exacerbate associated disservices. We posit that one reason for the neglect of ecosystem disservices from the discourse and policy debates around ecosystems and human wellbeing is because there is no widely accepted definition or typology of ecosystem disservices. Here, we briefly examine current understandings of the term ecosystem disservices and offer a definition and a working typology to help generate debate, policy and management options around ecosystem disservices. We differentiate ecosystem disservices from natural hazards and social hazards, consider some of their inherent properties and then classify them into six categories. A variety of examples are used to illustrate the different types of, and management strategies to, ecosystem disservices.
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Density and regrowth of a forest restio (Ischyrolepis eleocharis) under harvest and non-harvest treatments in dune forests of Eastern Cape Province, South Africa
- Authors: Ruwanza, Sheunesu , Shackleton, Charlie M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180828 , vital:43649 , xlink:href="https://doi.org/10.1007/s12231-015-9306-y"
- Description: Ischyrolepis eleocharis (Mast.) H.P.Linder is a perennial rush or sedge-like herb in the Restionaceae family and has been harvested for various uses from coastal forest dunes of South Africa. Around 2005, a ban on I. eleocharis harvesting in Bathurst coastal forest was instituted by provincial conservation authorities based on their unsubstantiated impression that the species population was decreasing. Here we report on the population density pre and post the harvest ban, as well as further explore the autecology of the species by assessing plant density relative to environmental factors (slope and aspect) and a controlled experiment on regrowth after harvesting at different intensities. The results show that the shoot density of both living and dead I. eleocharis increased significantly over the past eight years. This concurs with results from the harvesting experiment which showed that I. eleocharis recovered rapidly within a year of harvesting. Both aspect and slope play a key role in the distribution of I. eleocharis, with most plants found in open patches in the forest located on the summit and upper slopes of dunes facing the landward side. These results indicate that I. eleocharis is highly abundant and resilient to harvesting.
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