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  • Coetsee, Corli  (4)
  • Biology  (4)
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  • Biology  (4)
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  • 1
    Online Resource
    Online Resource
    Cambridge University Press (CUP) ; 2013
    In:  Journal of Tropical Ecology Vol. 29, No. 1 ( 2013-01), p. 49-60
    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
    RVK:
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2013
    detail.hit.zdb_id: 1466679-0
    SSG: 12
    SSG: 23
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  • 2
    In: Biotropica, Wiley, Vol. 51, No. 5 ( 2019-09), p. 682-691
    Abstract: Bark damage resulting from elephant feeding is common in African savanna trees with subsequent interactions with fire, insects, and other pathogens often resulting in tree mortality. Yet, surprisingly little is known about how savanna trees respond to bark damage. We addressed this by investigating how the inner bark of marula ( Sclerocarya birrea ), a widespread tree species favoured by elephants, recovers after bark damage. We used a long‐term fire experiment in the Kruger National Park to measure bark recovery with and without fire. At 24 months post‐damage, mean wound closure was 98, 92, and 72%, respectively, in annual and biennial burns and fire‐exclusion treatments. Fire exclusion resulted in higher rates of ant colonization of bark wounds, and such ant colonization resulted in significantly lower bark recovery. We also investigated how ten common savanna tree species respond to bark damage and tested for relationships between bark damage, bark recovery, and bark traits while accounting for phylogeny. We found phylogenetic signal in bark dry matter content, bark N and bark P, but not in bark thickness. Bark recovery and damage was highest in species which had thick moist inner bark and low wood densities (Anacardiaceae), intermediate in species which had moderate inner bark thickness and wood densities (Fabaceae) and lowest in species which had thin inner bark and high wood densities (Combretaceae). Elephants prefer species with thick, moist inner bark, traits that also appear to result in faster recovery rates.
    Type of Medium: Online Resource
    ISSN: 0006-3606 , 1744-7429
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2052061-X
    SSG: 12
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  • 3
    In: Ecology, Wiley, Vol. 101, No. 5 ( 2020-05)
    Abstract: Although studies have shown that mammalian herbivores often limit aboveground carbon storage in savannas, their effects on belowground soil carbon storage remain unclear. Using three sets of long‐term, large herbivore exclosures with paired controls, we asked how almost two decades of herbivore removal from a semiarid savanna in Laikipia, Kenya affected aboveground (woody and grass) and belowground soil carbon sequestration, and determined the major source (C 3 vs. C 4 ) of belowground carbon sequestered in soils with and without herbivores present. Large herbivore exclusion, which included a diverse community of grazers, browsers, and mixed‐feeding ungulates, resulted in significant increases in grass cover (~22%), woody basal area (~8 m 2 /ha), and woody canopy cover (31%), translating to a ~8.5 t/ha increase in aboveground carbon over two decades. Herbivore exclusion also led to a 54% increase (20.5 t/ha) in total soil carbon to 30‐cm depth, with ~71% of this derived from C 4 grasses (vs. ~76% with herbivores present) despite substantial increases in woody cover. We attribute this continued high contribution of C 4 grasses to soil C sequestration to the reduced offtake of grass biomass with herbivore exclusion together with the facilitative influence of open sparse woody canopies (e.g., Acacia spp.) on grass cover and productivity in this semiarid system.
    Type of Medium: Online Resource
    ISSN: 0012-9658 , 1939-9170
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 1797-8
    detail.hit.zdb_id: 2010140-5
    SSG: 12
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  • 4
    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
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 2052061-X
    SSG: 12
    Location Call Number Limitation Availability
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