Factors influencing survivorship of Portulacaria afra cuttings in restoration of degraded lands

Heavy over-browsing, over-grazing, and over-trampling has caused the degradation of vast areas of subtropical thicket, including parts of the Greater Addo Elephant National Park (GAENP). Severe degradation has resulted in the loss of vegetation cover and the deterioration of soils and soil functioning. The South African Department of Environmental Affairs (DEA), and specifically the Natural Resource Management Programme (NRM), have invested in restoration initiatives such as the Subtropical Thicket Restoration Programme (STRP), which has aimed to demonstrate the logistical and practical feasibility of restoring these degraded thickets by planting en masse Portulacaria afra (spekboom) cuttings. However, the planted P. afra cuttings often succumb to various abiotic and biotic stresses. This project aimed to identify various factors which may influence the survival of P. afra cuttings, including i) soil properties, ii) water (rainfall, infiltration, run-off, etc.), iii) browsing by mega-herbivores, iv) topographical features such as slope and aspect, or v) plant species or communities. Biodiversity and carbon baselines were carried out at 50 plots within the Main Camp, Darlington and Kabouga sections of the GAENP, providing pre-planting vegetation and soil data. The en masse planting of P. afra occurred following the completion of the baselines. Following a minimum rest period of three months after planting, survivorship counts were carried out at all plots. Infiltration rate had a significant positive relationship with planted P. afra survivorship across all of the sites. Positive trends between increases in litter and root biomass and planted P. afra cuttings survivorship in Kabouga were also evident. Magnesium, water-holding capacity and increasing soil clay percentage were found to have a significant negative relationship with planted P. afra survivorship in Kabouga. Aluminium, magnesium, and boron all had significant positive relationships with planted P. afra cuttings survivorship in Addo Main Camp. No soil variables had any significant relationship with survivorship of planted P. afra cuttings at Darlington. The presence of elephants (Loxidonta africana) had a significant negative relationship with planted P. afra survivorship. Plant communities in more ‘moderately’ degraded states, characterized by the retention of canopy dominant species, woody vegetation cover, limited bareground and higher cover of litter had higher survivorship of planted P. afra cuttings than those in more severely degraded states. The grass Panicum maximum, and forb Atriplex semibaccata were associated with positive relationships with planted P. afra survivorship across all sites. Future research should aim to develop matrices which plot likely survivorship percentages with parameters of measurable variables, such as infiltration, severity of soil capping, browsing densities, chemical indicators, and degradation severity, to identify suitable biophysical planting conditions for P. afra cuttings. Further research should assess whether the presence of elephants, in high densities, can reduce the economic feasibility of the en masse plantings of P. afra cuttings in attempts to restore degraded landscapes

Data from: Community-level responses of African carnivores to prescribed burning

Fires are common in many ecosystems worldwide, and are frequently used as a management tool. Although the responses of herbivores to fire have been well-studied, the responses of carnivores to fire remain unclear. In particular, post-fire habitat changes, and the associated changes in prey availability, might affect the coexistence or competition of carnivore species within the larger carnivore community, but few studies have focused on how fires influence multiple carnivore species simultaneously. Using South African carnivores as our focal community, we explored relative changes in carnivore intensity of use in post-fire landscapes associated with hypothesized changes in prey availability and top-down suppression. We monitored carnivore intensity of use in relation to prescribed burning using camera traps, with a Before-After-Control-Impact study design. We analyzed the camera trap data using community N-mixture models to understand how individual species, as well as the carnivore guild as a whole, respond to burning. Changes in carnivore intensity of use in response to prescribed burns were not uniform; however, no species decreased intensity of use of post-fire landscapes. The apex predator, the lion (Panthera leo), increased use of prey-rich burnt areas, but other large carnivore species exhibited neutral responses to fire despite the associated prey increase. Responses of medium- and small-sized carnivores were species-specific, and included both neutral and positive responses. Positive responses to fire by lions and herbivores were short-lived, and did not persist a year after burning occurred. Synthesis and Applications: Our results indicate that fire does not promote carnivore coexistence by creating conditions for all carnivores to increase use of burned areas, but that it also likely does not result in spatial avoidance of subordinate predators. Instead, fires might cause a suppression of opportunities for subordinate large carnivores because they need to avoid the apex predator, rather than take advantage of short-term increased hunting opportunities in recently burned areas. Our results highlight the complexity of understanding species-specific and community-level responses of carnivores to fire, and overlooked ecological effects of its use as a management tool

Data from: Context-dependency of top-down, bottom-up, and density-dependent influences on cheetah demography

1. Research on drivers of demographic rates has mostly focused on top predators and their prey, and comparatively less research has considered the drivers of mesopredator demography. Of those limited studies, most focused on top-down effects of apex predators on mesopredator population dynamics, whereas studies investigating alternative mechanisms are less common. 2. In this study, we tested hypotheses related to top-down, bottom-up, and density-dependent regulation of demographic rates in an imperiled mesopredator, the cheetah (Acinonyx jubatus). 3. We used a 25-year dataset of lion density, cheetah density, and prey density from the Mun-Ya-Wana Conservancy in South Africa and assessed the effects of top-down, bottom-up, and density-dependent drivers on cheetah survival and reproduction. 4. In contrast to the top-down and bottom-up predications, both adult and juvenile cheetahs experienced the lowest survival during months with high prey densities and low lion densities. We only observed support for a density-dependent response in juvenile cheetahs, where they had a higher probability of reaching independence during times with low cheetah density, and low prey density. We did not identify any strong drivers of litter size. 5. Collectively, our results indicate that high apex predator abundance might not always have negative effects on mesopredator populations, and suggest that context dependency in top-down, bottom-up, and density-dependent factors may regulate demographic rates of cheetahs and other mesopredators. Our results highlight the complexities of population-level drivers of cheetah demographic rates and the importance of considering multiple hypotheses of mesopredator population regulation