| 1. |
- Ekblom, Anneli, et al.
(författare)
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A Historical Ecology of the Limpopo and Kruger National Parks and Lower Limpopo Valley
- 2011
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Ingår i: Journal of Archaeology and Ancient History. - Uppsala : Department of Archaeology and Ancient History. - 2001-1199. ; 1:1, s. 1-29
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Tidskriftsartikel (refereegranskat)abstract
- The paper uses new palaeo-ecological data and a selective review of archaeological and written sources to show how social and natural history over the last 1200 years have interacted to form the present day landscape of Limpopo National Park and Northern Kruger National Park. The long-term mosaic of different communities in this landscape, hunter and gatherers, pastoralists, farmers and traders has, over time, contributed to shape and reshape a heterogeneous landscape. While some features in this landscape, such as water scarcity, have remained stable over time, there have also been major transformations in both the physical landscape and social life. The natural mosaics have been utilised and enhanced over time and the combination of natural and cultural mosaics are reflected in the landscape through archaeological sites, the pollen record and in the present day landscape.
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| 2. |
- Ekblom, Anneli, 1969-, et al.
(författare)
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Dung fungi as indicators of past herbivore abundance, Kruger and Limpopo National Park
- 2010
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 296:1-2, s. 14-27
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Tidskriftsartikel (refereegranskat)abstract
- Effective wildlife management needs historical data on herbivore abundance and its interactions with vegetation, climate and disturbance over longer time periods than is available through observational and archive data. Spores specific to herbivore dung provide a potential source of information on past herbivore abundances. This paper sets out to evaluate the potential of fungal spores as environmental indicators and in particular the use of coprophilous fungi in understanding past herbivore densities and their impact on the savanna landscape of Kruger and Limpopo National Parks (South Africa and Mozambique). Spore assemblages from six sedimentary cores are analysed and compared with the pollen data. Spores of coprophilous fungi, Coniochaeta cf ligniaria, and Sordariaceae in particular provide a valuable source of information about past herbivore densities. The spore assemblages of investigated localities show historical fluctuations in herbivore abundance. Peaks in wild/domestic herbivore densities can be seen, on a local scale from 800– 900 AD and another at 1400 AD, however, these cannot be linked with any significant changes in vegetation. The last 200-300 years have seen an increased abundance of herbivores in the Limpopo floodplain sites, particularly domestic cattle. There is no clear correspondence between changes in herbivore abundance and local vegetation in this period or the 20th century. However, domestic cattle, together with wild herbivores, probably contributed to creating a mosaic type of landscape with heterogeneous tree cover.
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| 3. |
- Ekblom, Anneli, 1969-, et al.
(författare)
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Fire history and fire ecology of Northern Kruger (KNP) and Limpopo National Park (PNL), southern Africa
- 2010
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 20:7, s. 1063-1077
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Tidskriftsartikel (refereegranskat)abstract
- This paper explores the general correlations between fire and grass/tree relationships, as represented by fossil charcoal and pollen, from different vegetation types in the savanna ecosystems of the neighbouring Kruger (KNP) and Limpopo (PNL) national parks. Our analysis suggests that the basic presumption that fire is a main driver of vegetation dynamics in the savanna ecosystem by suppressing tree seedlings and encouraging grasses needs to be re-examined. An improved approach is to understand how fire may act both as a negative and positive feedback in different vegetational phases and both as a driver and responder in transitions between phases. The correlation between arboreal pollen (AP) percentages and charcoal influx suggests that in the grassland phase (< 5% AP), fire acts as a driver of woody recruitment and as a positive feedback, i.e. potentially driving the system to shift into a savanna phase. In the savanna phase (5–10% AP) fire limits woody recruitment and acts as a negative feedback in maintaining the savanna. Thus, in the savanna phase other factors than fire alone drive the transition from savanna to woodland-forest. In the riparian phase, where evidence of farming is present particularly from ad 1600 onwards, fire appears to facilitate tree recruitment where AP ranges between c. 10 and 20% AP. Though a decline in AP abundance can be seen contemporaneously with charcoal peaks, our analysis suggests that overall, human-induced fires do not seem to have a negative impact on woody cover. Our results have implications for fire management as riparian-dominated phases and savannas with a sufficient woody cover are less sensitive to changes in fire policies than open grasslands that may, with a change in fire frequency, change into another state.
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| 4. |
- Ekblom, Anneli, 1969-, et al.
(författare)
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Hierarchy and scale : testing the long term role of water, grazing and nitrogen in the savanna landscape of Limpopo National Park (Mozambique)
- 2010
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 25:10, s. 1529-1546
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Tidskriftsartikel (refereegranskat)abstract
- This paper compares vegetation dynamics at two sites in the savanna landscape of Limpopo National Park (PNL), Mozambique. In order to test the relationship between vegetation cover and hydrology, nutrient availability and disturbance from grazing and fire over the last 1,200 years at local (100 m2) scales, we use palaeoecological data (i.e. pollen assemblages, charcoal abundance, C/N ratio, stable isotopes and herbivore-associated spore abundance). Two pans governed by similar rainfall regimes (on average 600 mm/year) but different hydrologies are compared. Chixuludzi Pan is responsive to the Limpopo River and is more water rich than Radio Pan, which is situated in a dry landscape with little surface water. The analysis suggests that in savannas where water is scarce, the recruitment of woody taxa is constrained mainly by the availability of underground water. In the Radio Pan sequence, the present grassland savanna has been stable throughout the time studied. In contrast, the Chixuludzi Pan savanna landscape where local hydrology, due to the proximity of Limpopo River, allows for a higher water availability the relationship between grass-arboreal pollen suggests a greater variability in vegetation cover, and other factors such as grazing, herbivory and nitrogen availability are important as controlling mechanisms for woody cover. The historical depth of the analysis enables a sub-hierarchy of local scale process to be identified, in this case local hydrology. Local water availability is shown to override the effect of regional rainfall and, in turn, to control the influence of other local scale factors such as nutrients and grazing.
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| 5. |
- Ekblom, Anneli, 1969-, et al.
(författare)
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Rainfall variability and vegetation dynamics of the lower Limpopo Valley, Southern Africa, 500 AD to present
- 2012
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 363, s. 69-78
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Tidskriftsartikel (refereegranskat)abstract
- The long-term responses of vegetation to climate variability are of relevance for predicting present and future vegetation change, and have implications for the management of savanna and riparian ecosystems. This paper explores the links between regional rainfall, hydrology and vegetation dynamics in the savannas and riverine forests of the lower Limpopo Valley, southern Africa, from 800 AD to the present, reviewing palaeoecological data (fossil pollen, spores, diatoms and lithology) from several hydrological systems in Kruger National Park (KNP), South Africa and Limpopo National Park (PNL), Mozambique. The PNL-KNP records show that riverine arboreal taxa expanded during wetter periods, including 800-1400 AD and after 1800 AD. Between 1400 and 1800 AD, grasses, savanna taxa and generalist taxa were favored over riparian taxa, a change that is linked with the onset of dry spells in the region (corresponding to the so-called Little Ice Age). The most extreme drought events around 1700 AD resulted in a marked decline of riparian forest taxa near Lake Mapimbi, KNP. In contrast, many water-scarce sequences away from the riverine environment, such as Radio Pan, Mafayeni Pan, Malahlapanga Pan and Lake Makwadzi show stable grassland vegetation throughout the last 1200 years. The results demonstrate the resilience of the grassland-savanna ecosystems to projected climate change with warmer and overall drier climate. The riverine forests are predicted to be more vulnerable especially as more extreme weather events are projected.
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