Jessica Allen

• Ph.D.
• Consultant at SLR

Macrotermes termite mounds in the Kruger National Park occupy a significant part of the savanna landscapes, occurring at densities of up to 70 km⁻² and often exceeding 10 m in width and 4 m in height. The mounds are usually devoid of trees, but have dense grass cover in wet years. As a result, these mounds form large patches of grassland amongst th...

Treeless grasslands occur within landscapes that are predominantly wooded savannas in the central Kruger National Park, South Africa. As a first step in identifying soil properties potentially underpinning differences in vegetation structure in these landscapes, we analysed the soil chemistry of the pedoderm (0–2 cm) in a grassland and two adjacent...

The small tree, Dichrostachys cinerea, occurs in dense patches within grasslands on gabbro-derived soils in the southern Kruger National Park. It is not known whether soil properties in the grasslands affect tree establishment. As a first step in identifying soil properties potentially underpinning differences in vegetation structure, we analysed t...

The woody plant, Colophospermum mopane, occurs as either a shrub or tree in shrublands and woodlands, respectively, in the central Kruger National Park, South Africa. As a first step in identifying which soil properties potentially influence the structure of C. mopane in these landscapes, we investigated the soil chemistry of the pedoderm in shrubl...

Invasion by invasive alien trees is a major threat to the biodiversity of the fynbos biome in South Africa. The environmental factors influencing the intensity of invasion are, however, largely unknown. In particular, the effects of soil nutrients on the invasion of alien trees in the fynbos biome have not been investigated. The Catabolic Theory pr...

Ecologists often use indices or proxies to communicate complex ecological entities. Indices commonly known as thermal safety margin, habitat thermal quality and hours of restriction describe species’ vulnerability to climate change by comparing organisms’ thermal limits or preferences to available habitat temperatures. Ready access to temperature d...

Intensive goat farming has transformed more than a million hectares of subtropical thicket in South Africa from a dense closed-canopy shrubland into an open savanna-like system. Restoration of the degraded thicket landscapes can be achieved by planting truncheons of spekboom (Portulacaria afra). The sale of carbon sequestered by spekboom can potent...

Critical thermal limits form an increasing component of the estimation of impacts of global change on ectotherms. Whether any consistent patterns exist in the interactive effects of rates of temperature change (or experimental ramping rates) and acclimation on critical thermal limits and warming tolerance (one way of assessing sensitivity to climat...

The weevil Cyrtobagous salviniae Calder & Sands 1985 (Family: Curculionidae) is a highly effective biocontrol agent for the invasive water fern Salvinia molesta D.S. Mitchell (Family: Salviniaceae). The life histories of both organisms are affected by temperature, making the potential impacts of climate change on efficacy of control an important ar...

Critical thermal limits provide an indication of the range of temperatures across which organisms may survive, and the extent of the lability of these limits offers insights into the likely impacts of changing thermal environments on such survival. However, investigations of these limits may be affected by the circumstances under which trials are u...