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  • Bond, William J.  (5)
  • Coetsee, Corli  (5)
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  • 1
    Online Resource
    Online Resource
    Low gains in ecosystem carbon with woody plant encroachment in a South African savanna
    Cambridge University Press (CUP) ; 2013
    In:  Journal of Tropical Ecology Vol. 29, No. 1 ( 2013-01), p. 49-60
    Details
    In: Journal of Tropical Ecology, Cambridge University Press (CUP), Vol. 29, No. 1 ( 2013-01), p. 49-60
    Abstract: Total ecosystem carbon storage has frequently been found to increase with woody encroachment in savannas. However the loss of grass roots associated with woody encroachment can lead to a decrease in below-ground carbon storage which is not compensated for by an increase in above-ground carbon. To investigate how the extent of total woody cover affected ecosystem carbon, soil and above-ground carbon storage along eight thicket–savanna and five forest–grassland boundaries were measured. To investigate whether changes in soil carbon concentrations were related to the percentage of C4 (grass) roots to total roots and root quantity and quality, we measured fine-root biomass, root C : N ratios, root N, and % C4 roots at three different depths across thicket patches of different ages (n = 189). Forests contained significantly more carbon than adjacent grasslands in both above-ground carbon (mean difference 12.1 kg m −2 ) and in the top 100 cm of the soil (mean difference 4.54 kg m −2 ). Thickets contained significantly more above-ground carbon than adjacent savannas (3.33 kg m −2 ) but no significant differences in soil carbon were evident. Total fine-root biomass appeared to be more important than root quality (root C : N) in determining soil carbon concentrations during the encroachment process (i.e. in thicket of different ages). Similarly for thickets, the % C4 roots had no significant effect on soil carbon concentrations. In conclusion, thicket invading into open savanna vegetation did not lead to significant gains in ecosystem carbon at this study site. Significant gains were only evident in mature forest, suggesting that the process may take place very slowly.
    Type of Medium: Online Resource
    ISSN: 0266-4674 , 1469-7831
    URL: Article
    DOI: 10.1017/S0266467412000697
    RVK:
    WA 15000
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2013
    detail.hit.zdb_id: 1466679-0
    SSG: 12
    SSG: 23
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    Online Resource
  • 2
    Online Resource
    Online Resource
    What do ecologists miss by not digging deep enough? Insights and methodological guidelines for assessing soil fertility status in ecological studies
    Elsevier BV ; 2013
    In:  Acta Oecologica Vol. 51 ( 2013-8), p. 17-27
    Details
    In: Acta Oecologica, Elsevier BV, Vol. 51 ( 2013-8), p. 17-27
    Type of Medium: Online Resource
    ISSN: 1146-609X
    URL: Article
    DOI: 10.1016/j.actao.2013.05.007
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2013
    detail.hit.zdb_id: 2003658-9
    SSG: 12
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Leaf traits of African woody savanna species across climate and soil fertility gradients: evidence for conservative versus acquisitive resource‐use strategies
    Wiley ; 2016
    In:  Journal of Ecology Vol. 104, No. 5 ( 2016-09), p. 1357-1369
    Details
    In: Journal of Ecology, Wiley, Vol. 104, No. 5 ( 2016-09), p. 1357-1369
    Abstract: Establishing trade‐offs among traits and the degree to which they covary along environmental gradients has become a key focal point in the effort to develop community ecology into a predictive science. While there is evidence for these relationships across global data sets, they are often too broad in scale and do not consider the particularities of local to regional species pools. This decreases their usefulness for developing predictive models at scales relevant for conservation and management. We tested for trade‐offs between traits and relationships with environmental gradients in trees and shrubs sampled across southern African savannas and explored evidence for acquisitive versus conservative resource‐use strategies using a phylogenetically explicit approach. We found a distinct trade‐off between two major poles of specialization indicative of acquisitive (high leaf nitrogen concentration, leaf phosphorus concentration, leaf N:P, specific leaf area and average leaf area) and conservative resource‐use strategies (high leaf carbon to nitrogen ratios (C:N), tensile strength and leaf dry matter content). Although we found that trait variance and species occurrence were constrained by phylogeny, phylogenetically informed analyses did not contradict non‐phylogenetic analyses, strengthening relationships in most cases. The high intrasite trait variability and weak relationships with soils and climate may in part be explained by the high levels of deciduousness and disturbance (i.e. fire and herbivory) inherent in African savannas. Synthesis . The relationships between traits and between traits and environmental gradients were far weaker than, and often contradictory to, broad‐scale studies that compare these relationships across biomes and growth forms, cautioning against making generalizations about relationships at specific sites based on broad‐scale analyses.
    Type of Medium: Online Resource
    ISSN: 0022-0477 , 1365-2745
    URL: Issue
    URL: Article
    DOI: 10.1111/jec.2016.104.issue-5
    DOI: 10.1111/1365-2745.12598
    Language: English
    Publisher: Wiley
    Publication Date: 2016
    detail.hit.zdb_id: 3023-5
    detail.hit.zdb_id: 2004136-6
    SSG: 12
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Mammal Browsers and Rainfall Affect Acacia Leaf Nutrient Content, Defense, and Growth in South African Savannas
    Wiley ; 2015
    In:  Biotropica Vol. 47, No. 2 ( 2015-03), p. 190-200
    Details
    In: Biotropica, Wiley, Vol. 47, No. 2 ( 2015-03), p. 190-200
    Abstract: Five sets of herbivore exclosures situated in mesic and semi‐arid savannas in Hluhluwe‐ iM folozi Park, South Africa were used to investigate the effects of mammal browsers and savanna type on plant traits relating to leaf nutrient content, defense, and growth in seven Acacia species. Mostly, browsing did not significantly affect leaf nutrient content but for a few species ( i.e ., increasing foliar N and P, decreasing C/N, and total polyphenols). Browser effects on structural defenses tended to be more pronounced than for leaf nutrient content and chemical defenses, particularly for semi‐arid species, resulting in longer, thicker, and denser spines, and a lower bite size index on browsed plants for most semi‐arid species. Browsing had no significant effect on growth rates for all species. Secondly, we investigated the effect of savanna type (mesic vs. semi‐arid) on the same set of plant traits and growth rates. A trade‐off in defense strategy was evident where mesic species had lower quality leaves and invested more heavily in growth and chemical defenses, while semi‐arid species generally had higher nutrient content leaves and invested more in structural defenses and higher levels of ramification. These findings suggest that the previously documented trade‐off in plant growth, resprouting ability and architecture between herbivore versus fire‐adapted savanna woody species can possibly be extended to include browse quality and defense type.
    Type of Medium: Online Resource
    ISSN: 0006-3606 , 1744-7429
    URL: Issue
    URL: Article
    DOI: 10.1111/btp.2015.47.issue-2
    DOI: 10.1111/btp.12192
    RVK:
    WA 15000
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 2052061-X
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Herbivores shape woody plant communities in the Kruger National Park: Lessons from three long-term exclosures
    AOSIS ; 2014
    In:  Koedoe Vol. 56, No. 1 ( 2014-02-25)
    Details
    In: Koedoe, AOSIS, Vol. 56, No. 1 ( 2014-02-25)
    Abstract: The role of grazers in determining vegetation community compositions and structuring plant communities is well recognised in grassy systems. The role of browsers in affecting savanna woody plant communities is less clear. We used three long-term exclosures in the Kruger National Park to determine the effect of browsers on species compositions and population structures of woody communities. Species assemblages, plant traits relating to browsing and soil nutrients were compared inside and outside of the exclosures. Our results showed that browsers directly impact plant species distributions, densities and population structures by actively selecting for species with traits which make them desirable to browsers. Species with high leaf nitrogen, low total phenolic content and low acid detergent lignin appeared to be favoured by herbivores and therefore tend to be rare outside of the exclosures. This study also suggested that browsers have important indirect effects on savanna functioning, as the reduction of woody cover can result in less litter of lower quality, which in turn can result in lower soil fertility. However, the magnitude of browser effects appeared to depend on inherent soil fertility and climate.Conservation implications: Browsers were shown to have significant impacts on plant communities. They have noticeable effects on local species diversity and population structure, as well as soil nutrients. These impacts are shown to be related to the underlying geology and climate. The effects of browsers on woody communities were shown to be greater in low rainfall, fertile areas compared to high rainfall, infertile soils.
    Type of Medium: Online Resource
    ISSN: 2071-0771 , 0075-6458
    URL: Article
    DOI: 10.4102/koedoe.v56i1.1165
    Language: Unknown
    Publisher: AOSIS
    Publication Date: 2014
    detail.hit.zdb_id: 2413347-4
    SSG: 12
    SSG: 6,31
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