Reference : UMR5558-NATARB-043
Workplace : VILLEURBANNE
Date of publication : Tuesday, November 15, 2022
Scientific Responsible name : Hervé Fritz CNRS IRL-REHABS
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 December 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Miombo woodland is the most common savanna of the southern hemisphere. It has been by people since the early Stone Age and today these woodland resources are important to the livelihoods of the approximately 100 million people. The woody components of these systems play an important role in the ecosystem functioning of the miombo, particularly in nutrient cycling and the storing of carbon; but they are disappearing at a considerable rate. Elephants are another major source of disturbance for Miombo woodland, and have locally also created concerns about their sustainable use of Miombo species under artificially high densities, but possible recovery strategies have been suggested. Considering that Miombo woodlands have evolved under elephant disturbance, selected coping traits may also allow trees to respond and withstand similar pressure from humans, although these are not identical. Further, we should be able to use our understanding of elephant impacts to assess ecologically relevant or acceptable rates, those under which the ecosystem evolved, of human-caused tree loss.
One of the key traits of savanna trees that allows them to cope with disturbances and structural damages due to fire and megafaunal topkill is the ability to coppice (resprout). This trait also enables their recovery after human-induced damage by the harvesting of stems for fuelwood and timber. Resprout growth varies between species and is strongly influenced by damage height and pre-damage stem size. Limited research has been done on the effects of repeated damage/re-harvesting of resprouts, but evidence suggest that this impacts negatively on stored reserves, shoot diameter and shoot length, but it may stimulate increased shoot production per coppicing stump. Whether the change in growth and woody material quality would change the selection of coppiced tree by consumers is not well understood. Further, even though coppicing could enable sustainable fuelwood harvesting in woodlands, the long-term effects of repeated elephant vs human disturbances, or even combined, have had little attention. The consequences of changes in vegetation structure due to coppicing for the diversity of ecosystem services provided by Miombo woodlands is poorly understood. This PhD project aims at understanding the coppicing response and productivity of Miombo tree species to repeated disturbances from single or multiple sources (humans and elephants) and assess how their coppicing traits can still allow them to deliver key ecosystem services (fibre, energy, carbon sequestration). It has 4 objectives, though not all may be achieved in the PhD: (1): Investigate the shared preference by elephants and humans for miombo trees species, and associated traits (2) assess effects of repeated re-harvesting on coppice growth dynamics and possible consequences on harvesting strategies by humans and elephants; (3): Investigate implications of changes in vegetation structure and growth on carbon sequestration in human (or elephant or both) impacted savannas; (4): From acquired knowledge, elaborate an agent-based model to explore management scenarios of these woodlands under joint use by elephant and humans to meet conservation and sustainable livelihood objectives
The PhD will be carried out within a collaborative consortium, IRL-REHABS (CNRS-NMU), LBBE (CNRS-Univ Lyon1), Wits-APES, NMU-DptConservation, and will benefit from two long-tem study sites (1) the Wits Rural Facility and surrounding communal rangelands, where we will benefit from various post-harvest treatments applied to T. sericea and D. cinerea stumps cut at the same time, as well as 54 vegetation monitoring plots in communal rangelands in which we record and measure cut stems and coppice in natural vegetation around villages. (2) the Hwange LTSER site in Zimbabwe, including the Main Camp area of Hwange NP, the Sikumi Forest Area, and 9 villages from the periphery. The existing 12 long-term plots (25x50m) inside the parks and the 200 transects sites (2x25m transects) inside the forestry area and communal rangelands provide a unique setup to compare use by humans and elephants.
The PhD student will be spending time in the field in Zimbabwe (Hwange LTSER) and South Africa (Wits Rural Facility), will be hosted for a long period in South Africa at the IRL-REHABS. When in France, the student will be based at the LBBE, on the La Doua campus of University of Lyon 1.
Constraints and risks
This PhD has extensive field work in southern Africa, which means possible logistical constraints, hence the need for flexibility and adaptive capacity. However, the existing long-term field facilities and the South Africa based international research laboratory will allow for a smooth development of the subject. This PhD will imply long stays in South Africa and shorter stays in France, and this may add a constraint to candidates with strong bonds in France. The field work will have the common risks of collecting data in wild and rural areas of Africa, mostly related to the presence of wild animals, 4x4 driving, and fairly basic medical facilities on site, though high quality medical facilities are easily accessible in South Africa, not very far, in case of emergency.
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