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

Tokura, Wataru; Jack, Sam; Anderson, Tania A.; Hoffman, M. Timm

doi:10.4102/koedoe.v60i1.1473

Cited by 20 publications

(26 citation statements)

References 43 publications

(70 reference statements)

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“…Fieldwork was undertaken at the 33 km 2 Kuruman River Reserve (KRR; 26 • 58'S, 21 • 49'E) and neighboring farms in the southern African Kalahari. Droughts are a regular feature of the local climate (Jury, 2013;Tokura et al, 2018) and rainfall has been declining, and high temperature extremes increasing in both frequency and severity, over the last 20 years (Kruger and Sekele, 2013;van Wilgen et al, 2016;van de Ven, 2017).…”

Section: Methods Study Site and Systemmentioning

confidence: 99%

Compensatory Breeding in Years Following Drought in a Desert-Dwelling Cooperative Breeder

et al. 2020

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Variation in weather patterns can influence reproductive effort and success not only within but also between breeding seasons. Where environmental conditions can be highly variable between years, the weather, and particularly extreme weather events such as heat waves and droughts, may exert a strong influence on reproductive effort (number of breeding attempts) and success (number of surviving young) from one breeding season to the next. We used a 15-year dataset for a cooperatively breeding bird, the southern pied babbler Turdoides bicolor, to determine the impact of high temperatures and drought on reproductive effort and success. We tested the influence on reproductive effort and success of mean daily maximum air temperature and drought both within a breeding season, to determine the relative importance of current conditions, and during the previous breeding season, to determine the relative importance of compensatory effects in response to prior conditions. Reproductive effort and success were lower during breeding seasons characterized by drought, and higher in the breeding seasons that followed droughts, but were not predicted by mean daily maximum temperatures measured over the full length of the breeding season. We provide evidence of compensatory breeding following drought in a bird species endemic to a semi-arid ecosystem and suggest that compensatory mechanisms may be an important part of both long-term population persistence and post-drought population recovery.

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Section: Methods Study Site and Systemmentioning

confidence: 99%

Compensatory Breeding in Years Following Drought in a Desert-Dwelling Cooperative Breeder

et al. 2020

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“…The dominant vegetation type comprised Kalahari thornveld ( Acocks, 1988 ) and shrubby Kalahari dune bushveld on the plains ( Low and Rebelo, 1998 ). The aardvark study site was dominated by Gordonia duneveld vegetation ( Tokura, 2016 ). Large carnivores present were leopards ( Panthera pardus ) and cheetahs ( Acinonyx jubatus ).…”

Section: Methodsmentioning

confidence: 99%

“…Tswalu is situated within an area that is predicted to become hotter and drier under future climate change ( Engelbrecht et al, 2015 ), and already experiences low and highly variable rainfall, including sporadic droughts ( Thomas et al, 2007 ). The majority of rain falls between December and April ( Davis et al, 2010 ; Tokura, 2016 ). The hot season in which air temperatures peak at ∼35°C lasts from November to February, which overlaps with the period during which rainfall typically occurs.…”

Section: Methodsmentioning

confidence: 99%

“…Independent variables included photoperiod, minimum or maximum or range of 24-h air temperature, and vegetation greenness as a proxy of resource abundance for aardvark prey. This vegetation greenness index consisted of moderate-resolution imaging spectroradiometry (MODIS)-derived time-series enhanced vegetation index (EVI) data for the Gordonia duneveld vegetation ( Tokura, 2016 ). EVI was measured every 16 days and averaged per month.…”

Section: Methodsmentioning

confidence: 99%

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Increased Diurnal Activity Is Indicative of Energy Deficit in a Nocturnal Mammal, the Aardvark

et al. 2020

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Shifting activity to cooler times of day buffers animals from increased heat and aridity under climate change. Conversely, when resources are limited, some nocturnal species become more diurnal, reducing energetic costs of keeping warm at night. Aardvarks (Orycteropus afer) are nocturnal, obligate ant-and termite-eating mammals which may be threatened directly by increasing heat and aridity, or indirectly by the effects of climate change on their prey. We hypothesised that the minimum 24-h body temperature of aardvarks would decline during energy scarcity, and that aardvarks would extend their active phases to compensate for reduced resource availability, possibly resulting in increased diurnal activity when aardvarks were energetically compromised. To measure their thermoregulatory patterns and foraging activity, we implanted abdominal temperature and activity data loggers into 12 adult aardvarks and observed them for varying durations over 3 years in the Kalahari. Under non-drought conditions, aardvarks tightly controlled their 24-h body temperature rhythm (mean amplitude of the 24-h body temperature rhythm was 1.8 ± 0.3 • C during summer and 2.1 ± 0.1 • C during winter) and usually were nocturnal. During a summer drought, aardvarks relaxed the precision of body temperature regulation (mean 24-h amplitude 2.3 ± 0.4 • C) and those that subsequently died shifted their activity to progressively earlier times of day in the weeks before their deaths. Throughout the subsequent winter, the aardvarks' minimum 24-h body temperatures declined, causing exaggerated heterothermy (4.7 ± 1.3 • C; absolute range 24.7 to 38.8 • C), with one individual's body temperature varying by 11.7 • C within 8 h. When body temperatures were low, aardvarks often emerged from burrows during daytime, and occasionally returned before sunset, resulting in completely diurnal activity. Aardvarks also shortened their active periods by 25% during food scarcity, likely to avoid energetic costs incurred by foraging. Despite their physiological and behavioural

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“…Fire as a disturbance in semi-arid areas plays an intrinsic role in shaping biophysical attributes of savannah ecosystem by limiting biomass below its climatically determined potential (Singh et al, 2018). In addition to other biotic and abiotic factors, aboveground phytomass disturbance and variable plant responses to fire, leads to differences in the dynamics of plant phenology across semi-arid areas landscapes (Snyman, 2004;Tokura et al, 2018;Richter et al, 2019). These disturbances appear to have been responsible for a lower signal strength in the sub-region in 2009.…”

Section: Discussionmentioning

confidence: 99%

Savannah Phenological Dynamics Reveal Spatio-Temporal Landscape Heterogeneity in Karamoja Sub-region, Uganda

Egeru

Magaya

Kuule

et al. 2020

Front. Sustain. Food Syst.

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Phenological properties are critical in understanding global environmental change patterns. This study analyzed phenological dynamics in a savannah dominated semi-arid environment of Uganda. We used moderate-resolution imaging spectroradiometer normalized difference vegetation index (MODIS NDVI) imagery. TIMESAT program was used to analyse the imagery to determine key phenological metrics; onset of greenness (OGT), onset of greenness value, end of greenness time (EGT), end of greenness value, maximum NDVI, time of maximum NDVI, duration of greenup (DOG) and range of normalized difference vegetation index (RNDVI). Results showed that thicket and shrubs had the earliest OGT on day 85 ± 14, EGT on day 244 ± 32 and a DOG of 158 ± 25 days. Woodland had the highest NDVI value for maximum NDVI, OGT, EGT, and RNDVI. In the bushland, OGT occurs on average around day 90 ± 11, EGT on day 255 ± 33 with a DOG of 163 ± 36 days. The grassland showed that OGT occurs on day 96 ± 13, EGT on day 252 ± 36 with a total DOG of 156 ± 33 days. Early photosynthesis activity was observed in central to eastern Karamoja in the districts of Moroto and Kotido. There was a positive relationship between rainfall and NDVI across all vegetation cover types as well as between phenological parameters and season dynamics. Vegetation senescence in the sub-region occurs around August to mid-September (day 244–253). The varied phenophases observed in the sub-region reveal an inherent landscape heterogeneity that is beneficial to extensive pastoral livestock production. Continuous monitoring of savannah phenological patterns in the sub-region is required to decipher landscape ecosystem processes and functioning.

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

Cited by 20 publications

References 43 publications

Compensatory Breeding in Years Following Drought in a Desert-Dwelling Cooperative Breeder

Compensatory Breeding in Years Following Drought in a Desert-Dwelling Cooperative Breeder

Increased Diurnal Activity Is Indicative of Energy Deficit in a Nocturnal Mammal, the Aardvark

Savannah Phenological Dynamics Reveal Spatio-Temporal Landscape Heterogeneity in Karamoja Sub-region, Uganda

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