Investigating the environmental and anthropogenic spatio-temporal patterns of plant health of Welwitschia mirabilis in the central Namib Desert
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Date
2016-09
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Abstract
Environmental and anthropogenic patterns are the major factors that determine plant
persistence across the landscape over a long-term period. The spatio-temporal
patterns of vegetation distribution in the Namib Desert biome is attributed to the
climatic conditions, geomorphology and edaphic features. Landscape patterns in the
environmental conditions (e.g. rainfall and fog) of the Namib Desert have been
described as a complex gradient that has a major influence on vegetation over time.
Welwitschia mirabilis Hook. fil (Gnetales: Welwitschiaceae), commonly known as
Welwitschia, is one of the Namib Desert endemic species. Many surveys have
reported that desert plants, such as Welwitschia are well adjusted to environmental
stressors. Nevertheless, cumulative impacts (potential impacts include interference
with the water supply and deposition of dust) resulting from developments in the
central Namib such as uranium mines might significantly affect the Welwitschia plants’
survival. These impacts and the changing baseline conditions might affect their
physiological processes, thus their growth and reproduction.
In this study, we measured chlorophyll a fluorescence (as an indicator of
photosynthetic efficiency), leaf growth rate and cone dimensions to determine whether
there are spatial and temporal differences among Welwitschia plants across
catchments over time. The study showed a clear effect of topography, climatic
conditions and anthropogenic effects, with plants in different catchments being clearly
healthier than others during some months. We observed an increase in the
photosynthetic efficiency and leaf growth rate accelerated by the episodic rainfall that
occurred during January and April months across all catchments. Anthropogenic
effects such as browsing by domestic animals probably caused the reduction in
photosynthetic efficiency of plants located at the Welwitschia Wash catchment in
December. Plants that were located at Welwitschia campsite catchment had the
lowest photosynthetic efficiency and leaf growth rate throughout our investigation
when compared to plants in other catchments. We have established a baseline study
that can be used to develop a protocol to monitor the plant physiological status of
Welwitschia. In this way, the results from the study will feed into a management
strategy for this Welwitschia population. Apart from that, the findings may also aid
restoration as well as rehabilitation measures such as transplantation and reintroduction
of this unique plant by understanding its current functional health status
across the landscape and over time.
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Keywords
Welwitschia mirabilis, environment, agriculture, Namib Desert, desert plants
Citation
Shuuya, T. (2016) . Investigating the environmental and anthropogenic spatio-temporal patterns of plant health of Welwitschia mirabilis in the central Namib Desert (Unpublished master's thesis). Namibia University of Science and Technology, Windhoek.