A preliminary report on the dynamics of the vegetation of the Kalahari Gemsbok National Park

Rooyen, N. van; Rensburg, Daniël Janse van; Theron, G.K.; Bothma, Jacobus du P.

doi:10.4102/koedoe.v27i2.570

Cited by 11 publications

(12 citation statements)

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“…7a and b). In dry years, seedlings and saplings of A. erioloba suffer high mortality rates (Barnes, 2001;Theron et al, 1985;Van Rooyen and Van Rooyen, 1998;Van Rooyen et al, 1984). The concentration of wildlife in the riverbed could also have contributed towards the scarcity of young trees in the Nossob River.…”

Section: Population Structurementioning

confidence: 94%

Age determination of Acacia erioloba trees in the Kalahari

Steenkamp¹,

Vogel²,

Fuls³

et al. 2008

Journal of Arid Environments

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High quality wood core samples were collected from individual Acacia erioloba trees of unknown age in the Kgalagadi Transfrontier Park. In the majority of samples examined, seasonal changes were reflected in the wood anatomy as bands of marginal parenchyma on the polished surfaces of discs or cores. Estimated radiocarbon age was determined by means of 14 C analysis for all samples. There was a strong correlation between the annual growth ring count and estimated radiocarbon age. A correlation was also found between age and stem circumference. Age structure of several A. erioloba populations in the Kgalagadi Transfrontier Park was subsequently determined. It could be demonstrated that the populations growing in the bed of the Nossob River showed poor recruitment; however, no clear relationship was found between flooding and regeneration of A.erioloba in the riverbed. The population growing in the dune field had a healthy age structure.

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Section: Population Structurementioning

confidence: 94%

Age determination of Acacia erioloba trees in the Kalahari

Steenkamp¹,

Vogel²,

Fuls³

et al. 2008

Journal of Arid Environments

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“…These included significant increases in annual grass cover in the wet season or conversely, dieback in the dry season (Van Rooyen et al 1984). The EVI values typically increased with plant greening in late spring and summer, decreased in the late autumn and then remained low during the dry winter months.…”

Section: Spatio-temporal Patterns and Variability Of Vegetation Produmentioning

confidence: 99%

Long-term variability in vegetation productivity in relation to rainfall, herbivory and fire in Tswalu Kalahari Reserve

Tokura

Jack

Anderson³

et al. 2018

Koedoe

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Exploring the long-term influence of climate and land use on vegetation change allows for a more robust understanding of how vegetation is likely to respond in the future. To inform management, this study investigated the relationship between vegetation productivity trends and potential drivers of change in the 110 000 ha of the Tswalu Kalahari Reserve between 2000 and 2015, using the Moderate Resolution Imaging Spectroradiometer Enhanced Vegetation Index (EVI, MOD13Q1). Spatio-temporal variability of the EVI was mapped and then related to the historical records of precipitation, animal numbers and fire occurrences. Long-term trends in productivity were analysed by residual trend analysis (RESTREND). Significantly different EVI profiles were found between vegetation types, and this was related to the structure and function of the vegetation, as well as the effects of soil reflectance. The EVI time-series signalled spatial and temporal heterogeneity in plant productivity, which was strongly correlated with rainfall, although fire and especially herbivory had noteworthy localised effects on productivity. The RESTREND identified a significant positive trend in plant productivity in shrub-dominated vegetation types, providing evidence for the ongoing thickening of woody species. Significant negative trends in productivity were associated with artificial water points and more heavily stocked areas, leading to degradation.Conservation implications: The southern Kalahari has a highly variable rainfall regime, which is tied to a dynamic vegetation response. This variability should be taken into account when making management decisions. Field-based monitoring together with adaptive management approaches are needed in the face of an uncertain future in which significant warming is expected.

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“…Recruitment is episodic and occurs in wet years. During dry years, immature trees suffer high mortality (Van Rooyen et al 1984). Young trees tend to be closely spaced while old trees tend to be widely and randomly spaced (Jeltsch et al 1998).…”

Section: Characteristics Of Acacia Eriolobamentioning

confidence: 99%

Long‐term mortality patterns of the deep‐rooted Acacia erioloba: The middle class shall die!

Moustakas

Guenther

Wiegand

et al. 2006

J Vegetation Science

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Question: Is there a relationship between size and death in the long‐lived, deep‐rooted tree, Acacia erioloba, in a semi‐arid savanna? What is the size‐class distribution of A. erioloba mortality? Does the mortality distribution differ from total tree size distribution? Does A. erioloba mortality distribution match the mortality distributions recorded thus far in other environments? Location: Dronfield Ranch, near Kimberley, Kalahari, South Africa. Methods: A combination of aerial photographs and a satellite image covering 61 year was used to provide long‐term spatial data on mortality. We used aerial photographs of the study area from 1940, 1964, 1984, 1993 and a satellite image from 2001 to follow three plots covering 510 ha. We were able to identify and individually follow ca. 3000 individual trees from 1940 till 2001. Results: The total number of trees increased over time. No relationship between total number of trees and mean tree size was detected. There were no trends over time in total number of deaths per plot or in size distributions of dead trees. Kolmogorov‐Smirnov tests showed no differences in size class distributions for living trees through time. The size distribution of dead trees was significantly different from the size distribution of all trees present on the plots. Overall, the number of dead trees was low in small size classes, reached a peak value when canopy area was 20 ‐ 30 m2, and declined in larger size‐classes. Mortality as a ratio of dead vs. total trees peaked at intermediate canopy sizes too. Conclusion: A. erioloba mortality was size‐dependent, peaking at intermediate sizes. The mortality distribution differs from all other tree mortality distributions recorded thus far. We suggest that a possible mechanism for this unusual mortality distribution is intraspecific competition for water in this semi‐arid environment.

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A preliminary report on the dynamics of the vegetation of the Kalahari Gemsbok National Park

Cited by 11 publications

References 0 publications

Age determination of Acacia erioloba trees in the Kalahari

Age determination of Acacia erioloba trees in the Kalahari

Long-term variability in vegetation productivity in relation to rainfall, herbivory and fire in Tswalu Kalahari Reserve

Long‐term mortality patterns of the deep‐rooted Acacia erioloba: The middle class shall die!

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