Joh R. Henschel

Joh R. Henschel
South African Environmental Observation Network · Arid Lands Node

PhD

About

180
Publications
69,306
Reads
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4,176
Citations
Citations since 2016
31 Research Items
1885 Citations
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
Introduction
Joh R. Henschel is the past manager of the SAEON Arid Lands Node, Kimberley, South Africa, and past director of the Gobabeb Namib Research Institute, Namibia. He is a research associate of these institutions as well as of the University of the Free State. Joh is an ecologist, mostly concerning arid regions, ecohydrology, ecophysiology and population ecology. Current projects concern locusts, tenebrionid beetles, and drivers of ecosystem change.
Additional affiliations
January 1994 - March 1996
University of Wuerzburg
Position
  • Research Associate
Description
  • postdoc: Alexander von Humboldt Fellow
January 1982 - June 1986
University of Pretoria
Position
  • Research Assistant
Description
  • PhD student and junior lecturer
January 1981 - December 1981
University of Cape Town
Position
  • Research Assistant
Description
  • MSc student and Research Assistant

Publications

Publications (180)
Article
Full-text available
Woody structure, particularly that created by large trees, is crucial to savanna biodiversity pattern and process. We assessed changes in vertical and horizontal canopy over 15 years of saplings of Vachellia (Acacia) erioloba (camelthorn), a keystone species and one of the only trees to grow large in arid savanna on low rainfall areas of Kalahari s...
Article
Full-text available
Psammotermes allocerus Silvestri, 1908 is the only described species representing the genus Psammotermes Desneux, 1902 in Southern Africa. The large geographical range of this subterranean termite covers both summer and winter rainfall regimes. Deadwood is the preferred food when available, but in more arid habitats, both live and dead grasses form...
Article
We document changes in rangeland during a prolonged drought in the arid Karoo. Rangeland in this arid region is species-rich and dominated by a mixture of long-lived succulent and non-succulent shrubs. Ranching has led to the domination of vegetation by less palatable species, and resting does little to restore diversity because most species are lo...
Article
Full-text available
A part of the Square Kilometre Array (SKA) will be constructed in the northern Karoo of South Africa on approximately 135 000 ha of land. This land is formerly privately owned rangelands (farms) that were purchased by the South African National Research Foundation (NRF), on which the South African Radio Astronomy Observatory, as part of the global...
Article
Full-text available
Noy-Meir’s paradigm concerning desert populations being predictably tied to unpredictable productivity pulses was tested by examining abundance trends of 26 species of flightless detritivorous tenebrionid beetles (Coleoptera, Tenebrionidae) in the hyper-arid Namib Desert (MAP = 25 mm). Over 45 years, tenebrionids were continuously pitfall trapped o...
Article
Full-text available
1. Circular bare patches occur in high numbers among the vegetation of the Namib Desert margin. There is an ongoing scientific debate on the origin of these so‐called “fairy circles” (FCs). One of the most frequently discussed hypotheses regards the bare patches to be the result of localised herbivory by sand termites of the genus Psammotermes (fam...
Article
Full-text available
The future of fog‐dependent habitats under climate change is unknown but likely precarious; many have experienced recent declines in fog. Fog‐dependent deserts particularly will be threatened, because, there, fog can be the main water source for biota. We review the interactions between fog and fauna of the Namib Desert, about which there is 50 yr...
Article
Full-text available
Plant growth forms likely respond differently to disturbances such as trampling. We investigated the trampling effect of 1 600 sheep encamped at night in temporary enclosures (kraals, corrals or pens), which were relocated weekly. To examine trampling effects and regeneration rates of the various growth forms we compared vegeta- tion composition, c...
Article
Impacts of livestock farming include effects on arthropods and a range of related ecological processes. Grazing by sheep may indirectly affect web spider populations by changing vegetation structures available for web construction, or directly by trampling the spiders or their webs. We tested these two potential impacts by surveying spiders along t...
Article
We begin this essay with reflections on major research themes highlighted by the Karoo Special Issue (KSI). These include concerns over land-use change, long-term monitoring, climate change, governance and the need for more interdisciplinary research. We also identify some of the novel contributions of the KSI around these themes and highlight rese...
Article
The Karoo is an arid to semi-arid area across the western third of South Africa, comprising the Succulent Karoo and Nama-Karoo biomes. Its environment and people have experienced considerable changes, and now face new challenges as the Anthropocene unfolds. This Karoo Special Issue (KSI) brings together new information in 20 papers, a mixture of re...
Article
Full-text available
Tierberg-LTER is a research site established in 1987 in the semi-arid Succulent Karoo near Prince Albert in the Western Cape province, South Africa. The original purpose for its establishment was to study ecosystem dynamics and the drivers of vegetation in the context of historical land use. The large body of work that has materialised from Tierber...
Article
Full-text available
Welwitschia mirabilis is a long-lived evergreen in the hyperarid Namib Desert; at our study site, rainfall is rare (MAP=31 mm), groundwater deep (57-75 m), and fog frequent (50-90 events y-1). By examining root architecture in relation to soil moisture and analysing the isotopic composition of hydrogen and oxygen of plant and soil water, we establi...
Article
Full-text available
Through litter decomposition enormous amounts of carbon is emitted to the atmosphere. Numerous large-scale decomposition experiments have been conducted focusing on this fundamental soil process in order to understand the controls on the terrestrial carbon transfer to the atmosphere. However, previous studies were mostly based on site-specific litt...
Article
Full-text available
Although ephemeral rivers act as linear oases and play a fundamental role in sustaining regional biodiversity in dryland regions, little is known about these systems or their sensitivity to human impacts. Without such knowledge, it is difficult to manage or conserve them. Here, we conduct the first systematic investigation into the determinants of...
Article
Full-text available
Through litter decomposition enormous amount of carbon is emitted to the atmosphere. Numerous large-scale decomposition experiments have been conducted focusing on this fundamental soil process in order to understand the controls on the terrestrial carbon transfer to the atmosphere. However, previous studies were mostly based on site-specific litte...
Article
Full-text available
Through litter decomposition enormous amounts of carbon is emitted to the atmosphere. Numerous large-scale decomposition experiments have been conducted focusing on this fundamental soil process in order to under-stand the controls on the terrestrial carbon transfer to the atmosphere. However, previous studies were mostly based on site-specific litt...
Chapter
Full-text available
In this chapter we review and assess the potential impacts of fracking on Karoo ecosystems, based on related research from across the world, and interpreted in terms of the ecological characteristics and features of Karoo ecosystems. We highlight the dominant vegetation types, habitats and species which are characteristic or of conservation signifi...
Article
Full-text available
Ephemeral rivers act as linear oases in drylands providing key resources to people and wildlife. However, not much is known about these rivers' sensitivities to human activities. We investigated the landscape-level determinants of riparian tree dieback along the Swakop River, a dammed ephemeral river in Namibia, focusing on the native ana tree (Fai...
Poster
Full-text available
Regular dispersion of termite colonies is suggested to increase stability of biological communities. Our research will test generality of this hypothesis by investigating how the spatial characteristics (e.g. density and dispersion) of heuweltjies (raised earth mounds of the termite Microhodotermes viator) influence ecological processes at various...
Poster
Regular dispersion of termite colonies is suggested to increase stability of biological communities. Our research will test generality of this hypothesis by investigating how the spatial characteristics (e.g. density and dispersion) of heuweltjies (raised earth mounds of the termite Microhodotermes viator) influence ecological processes at various...
Article
The plains of the Nama-Karoo biome in southern Africa are characterised by a mixture of dwarf shrubs and grasses with near absence of shrubs and trees that are conspicuous in the adjacent savanna biome and on hills. We investigated the impact of a severe frost event in 2014 on the abundance and composition of woody vegetation in relation to local t...
Article
Full-text available
Welwitschia mirabilis is an ancient and rare plant distributed along the western coast of Namibia and Angola. Several aspects of Welwitschia biology and ecology have been investigated, but very little is known about the microbial communities associated with this plant. This study reports on the bacterial and fungal communities inhabiting the rhizos...
Data
Bar graph showing the phylum-level distribution of (a) bacterial and (b) fungal OTUs (97% cutoff). The taxonomic affiliation was performed using the Ribosomal Database Project Classifier (bacteria) and the UNITE database (fungi). (PDF)
Data
Venn diagram showing the number of shared phylotypes observed between the rhizosphere samples. a) bacteria, b) fungi. Sample nomenclature is as in S1 Table. (PDF)
Data
Fungal diversity. Sample nomenclature is as in S1 Table. (DOCX)
Data
Welwitschia plants dotted across an arid landscape (left). The exposed radial root system of a Welwitschia plant (right). (TIF)
Data
Rarefaction curves. a) bacteria, b) fungi. Sample nomenclature is as in S1 Table. (PDF)
Data
Bacterial diversity. Sample nomenclature indicates the sample type (S = bulk soil; R = rhizosphere), replicate (S = 1 to 5, R = 1 to 3) and pseudoreplicate (a, b). (DOCX)
Conference Paper
Full-text available
Heuweltjies are large, circular, raised mounds found in the Succulent Karoo biome of South Africa. Several theories exist as to the origin of heuweltjies, however there is a strong association between heuweltjies and termites. Two hundred and fifty heuweltjies have been identified on the 100 hectare Tierberg LTER area where the Tierberg Karoo Resea...
Article
Full-text available
Three decades ago a locust conference in Kimberley deliberated on the Brown Locust Locustana pardalina (Walker), its biology, feeding ecology, population dynamics, outbreak extent and frequency, swarm movements and artificial control of outbreaks. The current paper evaluates recommendations made at this conference. In contrast to the high levels of...
Article
Full-text available
The Namib Desert is hyper-arid in terms of rainfall, but its ecology is influenced by frequent fog events. Fog utilisation by Namib biota has been well studied, but its role in nutrient deposition and cycling, particularly with respect to soil processes, still has open questions. Given its potential for distinguishing between various ecosystem comp...
Article
Hypolithic microbial communities are productive niches in deserts worldwide, but many facets of their basic ecology remain unknown. The Namib Desert is an important site for hypolith study because it has abundant quartz rocks suitable for colonization and extends west to east across a transition from fog to rain dominated moisture sources. We show...
Article
Ephemeral rivers and the vegetation they support have numerous ecological and economic values to the mammals and people who rely on these systems. Yet, these crucial environments are believed to be threatened by exotic plant invasion. In Africa, invasive trees of the genus Prosopis have detrimental effects on native vegetation, bird and dung beetle...
Article
The dynamics of a small linear dune on the northern margin of the Namib Sand Sea have been monitored using erosion pins placed at the dune tip since 1969. GPS measurements of these pins enabled estimation of the rates of advance and lateral migration of the dune. The average rate of advance of the dune tip over the period 1969–2012 was 1.99 m yr–1...
Book
Full-text available
The objective of the Toktok Talkie book is to increase awareness and interest in biodiversity, ecological processes, the functions and services of nature, its uses and abuses, and environmental management, all in relation to human endeavours. While the departure point is the coastal Namib Desert and Atlantic shore , the topics embrace matters conce...
Article
Full-text available
The Namib is a relatively well-studied hyperarid desert. Much of the research effort was coordinated through the institutional framework of the Gobabeb Research and Training Centre, which was established in the middle of this desert fifty years ago. The initial discoveries focused on the Namib's remarkably high biodiversity and adaptations to deser...
Article
Full-text available
Individuals of most animal species are non-randomly distributed in space. Extreme climatic events are often ignored as potential drivers of distribution patterns, and the role of such events is difficult to assess. Seothyra henscheli (Araneae, Eresidae) is a sedentary spider found in the Namib dunes in Namibia. The spider constructs a sticky-edged...
Article
Full-text available
“Non rainfall” atmospheric water (dew, fog, vapour adsorption) supplies a small amount of water to the soil surface that may be important for arid soil micro-hydrology and ecology. Research into the direct effects of this water on soil is, however, lacking due to instrument and technical constraints. We report on the design, development, constructi...
Article
Full-text available
"Non-rainfall" water is important to the soil water balance and ecology of arid ecosystems. A component of this "non-rainfall" water in the Namib Desert, fog, exhibits spatial variation implying variability in composition and significance of each vector (dew, fog, vapour adsorption) to ecology at different locations. The composition of "non -rainfa...
Article
Full-text available
The Namib Desert along the southwestern coast of Africa is hyper-arid in terms of rainfall (<25 mm/yr), but experiences coastal fog deposition up to 100 days each year. The Namib is also home to the biologically anomalous, very long-lived and evolutionarily ancient gymnosperm Welwitschia mirabilis. Due to its perennial broad green leaves that appar...
Article
Full-text available
The effect of desert pavements (gravel mulch) on near surface soil micro-hydrology has been inadequately studied. Micro-hydrology in arid ecosystems occurs due to a daily non rainfall atmospheric water cycle, consisting of an input phase (dew, fog, vapour adsorption) and an evaporation phase. A winter comparative study between a bare soil (control)...
Conference Paper
Full-text available
Nutrient cycles (C, N and S) in the Namib Desert are investigated through a survey of �15N, �13C and �34S of plant material and soils along a fog gradient. The coastal Namib Desert in southwestern Africa is hyper-arid in terms of rainfall, but receives up to 100 days of fog each year. This climate regime leads to interesting water relations among t...
Article
Full-text available
In the Namib Desert seed distribution is greatly influenced by wind patterns. Existing literature regarding wind patterns over dunes focuses on two-dimensional simulations of flow over simplified dune structures. The three-dimensional geometries of the sand dunes suggests far more complex flow features exist, which are not captured by two-dimension...
Article
Full-text available
Black-backed jackals (Canis mesomelas, Schreber, 1775) survive in a wide range of environments. Their foraging strategies are highly variable in different habitats. Adaptations in foraging behaviour in relation to abundance and quality of food sources are expected to be highly pronounced in an extreme habitat like a desert. This study investigated...
Conference Paper
Full-text available
The Namib Desert on the southwestern coast of Africa is hyperarid in terms of rainfall (<25 mm/yr), but experi- ences up to 100 days of coastal fog each year. Active use of fog as a water source has been shown previously in Namib biota from (1) behavioral and water content studies of several Tenebrionid beetle species, and (2) tritiated water addit...
Article
The corolla spider (Araneae: Segestriidae: Ariadna) of the Namib Desert gravel plains typically places seven or eight stones in a circle around its burrow entrance. It was examined whether the spider selects and places stones according to physical characteristics. Circle composition can be explained by the allometric scaling to spider size of the b...
Article
Sexually dimorphic characters of Onymacris plana, a dune-living, solitary tenebrionid beetle of the Namib Desert, were tested for their roles in male-male fighting over females. Males were smaller than females but had extraordinarily wide elytra, with great variance in this characteristic. In males, but not in females, elytra width increased with b...
Article
Territorial behaviour of a clan of spotted hyaenas, Crocuta crocuta, was investigated in the Kruger National Park over a period of 27 months. These hyaenas were highly territorial, spending ⅕ of their total activities on territory patrol by scent-marking intensively and monitoring 64 marking posts, particularly in border regions. Females, the more...
Article
Full-text available
A systematic classification of Namib Desert darkling beetles (Coleoptera: Tenebrionidae) based on morphological characters is complicated as strong selection pressures exerted by desert conditions have led to a suite of convergent morphological characteristics. Here we present a first and preliminary insight into the relationships within the tribes...
Article
A systematic classification of Namib Desert darkling beetles (Coleoptera: Tenebrionidae) based on morphological characters is complicated as strong selection pressures exerted by desert conditions have led to a suite of convergent morphological characteristics. Here we present a first and preliminary insight into the relationships within the tribes...
Article
Full-text available
The status of six alien invasive plant species was investigated along the Lower Kuiseb River. The focus entailed a comparison of plants surveyed along transects located at five settlements of a rural community, with additional transects located between these settlements. While most living alien plants occurred in or adjacent to the main channel of...
Article
Full-text available
Different field methods of determining abundance and species diversity of darkling beetles (Coleoptera, Tenebrionidae) were tested. A combination of the use of pitfall traps and linear transect surveys served as the best rapid assessment of diversity, while pitfall traps alone are good for estimating abundance. Trap size (15cm diameter vs. 10cm dia...
Conference Paper
Full-text available
A steep rainfall gradient exists across the Namib Desert in southern Africa, which is unique in that frequent coastal fog occurs in areas that receive the least rainfall. Overall, the Namib is hyper-arid in terms of rainfall (25-100mm mean annual rainfall, MAR), but areas within about 60km of the coast see up to 100 days of fog each year. This scen...
Article
Full-text available
ecology, physiology, geology, geomorphology, archaeology and sociology. What, during this first phase of Mary’s career, were the keys to her success? It is clear that a convergence of fate, fortune and Mary’s own special brand of energy, focus and self-motivation, all worked in her favour. The locality and research function of Gobabeb provided the...
Article
Although the effects of grazing-induced savannah degradation on animal diversity are well documented, knowledge of how they affect space use or responding behaviour remains poor. In this study, we analysed space use of the spotted sand lizard (Pedioplanis l. lineoocellata) in degraded versus nondegraded habitats of southern Kalahari savannah habita...
Article
We used DNA fingerprints to determine whether the population structure and colony composition of the cooperative social spider Stegodyphus dumicola are compatible with requirements of interdemic (‘group’) selection: differential proliferation of demes or groups and limited gene flow among groups. To investigate gene flow among groups, spiders were...
Article
Water isotopes and the ecohydrology of fog in the Central Namib Desert: Initial results
Article
Birth and the early development of spotted hyaenas Crocuta crocuta has been documented for captive animals (Grimpe, 1916; Schneider, 1926; Pournelle, 1965; Golding, 1969) and in the wild (Kruuk, 1972). However, little is known of parturition and maternal behaviour in the first fortnight following parturition. The behaviour of one dam during this cr...
Article
Full-text available
Diet and foraging behaviour of three species of burrowing huntsman spiders, Leucorchestris arenicola, L. steyni and Carparachne aureoflava, from the Namib dunes were investigated over a three-year period. These nocturnal spiders are polyphagous predators that prey on more than 97 species of insects, arachnids and reptiles. Most prey were nocturnal...
Article
We studied the effects of overgrazing on the foraging behaviour of the lizard Pedioplanis l. lineoocellata (Spotted Sand Lizard), a sit-and-wait forager, in habitats of differing vegetation states to determine the effects of habitat degradation on this species. At high grazing intensity where vegetation cover and diversity is low, the lizard P. lin...
Article
Full-text available
Environmental controls on photosynthesis and N-cycling in Welwitschia mirabilis are evaluated through delta13C and delta15N analyses of leaf material from 26 individuals in the southermost population of this long-lived gymnosperm, which is endemic to the Namib Desert. The coastal Namib Desert in southwestern Africa is hyperarid in terms of rainfall...
Article
Full-text available
Climate and litter quality are primary drivers of terrestrial decomposition and, based on evidence from multisite experiments at regional and global scales, are universally factored into global decomposition models. In contrast, soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved...
Article
Full-text available
Studies in Namibia revealed the probability that L. kochi LAWRENCE 1965, known only from males, and L. arenicola LAWRENCE 1962, known only from females, could be synonyms. Taxonomic investigations of material from various museum collections as well as recently collected material of the type locality confirmed this suspect. Therefore, the name L. ko...