• Publicationsclose
• Research dataclose
• Other research productsclose
• 2012-2021close
• Other ORP type close

Fabaceae is the second most speciose plant family in the Core Cape Subregion (CCR) of South Africa, a Mediterranean type ecosystem, with mostly nutrient-poor soils. A majority of the legumes occurring in this region belong to the predominantly nitrogen-fixing subfamily Papilionoideae and they employ a variety of strategies for nutrient acquisition. However, legumes are neither uniformly nor randomly distributed in the CCR landscape. Instead, distinct legume species assemblages tend to occupy particular habitats within the landscape. The drivers of this distribution pattern are yet to be determined. In this thesis, it was hypothesized that edaphic factors (soil chemical and physical characteristics) and the distribution of rhizobia have influenced legume distributions in the CCR landscape. The influence of edaphic factors on the distribution of legume species assemblages in the Cape Peninsula (a microcosm of the CCR) is the subject of the second chapter of the thesis. It was hypothesized that the composition of legume species assemblages is correlated with soil physical and chemical properties and that the interaction of Phosphorus (P) and the three cations that often bind P, i.e. Aluminium, Calcium and Iron, making it unavailable to plants, drive legume species assemblages in the landscape. Soils from 27 legume sites, spanning all major soil types of the Cape Peninsula, were analysed for 31 chemical and physical properties. Surveys of legume species present at each site were conducted to generate a presence/absence matrix. Canonical correspondence analysis was used to test for a correlation between legume species composition and edaphic factors. The strength of the association between legume species composition and site groupings based on edaphic properties was assessed using indicator species analysis. A significant correlation between edaphic factors and species composition was found and the key edaphic parameters driving the relationship were clay content, iron (Fe), potassium (K), sulphur (S) and zinc (Zn). Indicator species, characteristic of the various edaphic habitats were also identified. These findings indicate that distinct edaphic habitats are occupied by discrete legume species assemblages, implying a significant influence of edaphic factors on the legume distributions. Chapter three of the thesis sought to determine if the ecological parameters; altitude, pH and soil type influence the distribution of the two main rhizobial genera (Burkholderia and Mesorhizobium) that nodulate various legumes of the CCR, and to determine the diversity and phylogenetic position of rhizobia that associate with the narrowly distributed and rare Indigofera superba in the CCR. The first objective was pursued through molecular characterisation of rhizobial strains isolated from nodules of legume species collected in the field across the Cape Peninsula. DNA sequences for 16S rRNA, recA and nodA were combined with data from a previous study that sampled broadly within the CCR and phylogenetic analyses were conducted. Tests for phylogenetic signals for the three ecological parameters were conducted, using the D statistic for soil type and Pagel’s λ for altitude and pH. These analyses were used to test the hypothesis that closely related species occupy similar habitats with respect to each of the three ecological parameters. For the study of rhizobial symbionts of Indigofera superba, field nodules were sampled from multiple populations across its distribution range and a phylogeny of its symbionts was reconstructed in a matrix that included symbionts of diverse legumes from different habitats within the CCR. The results showed that Burkholderia is restricted to acidic habitats, while Mesorhizobium occurs in both acidic and alkaline habitats. Additionally, both rhizobial genera showed significant phylogenetic clustering for pH and most soil types. However, none of the genera showed a phylogenetic structure with respect to altitude. These findings indicate that pH and soil type influence the distribution of rhizobia in the CCR. Implications of these findings for the distribution of legumes in the landscape are discussed. For the narrowly distributed I. superba, the results showed that it associates with diverse strains within the genus Burkholderia and such strains are not phylogenetically distinct from strains isolated from localities outside its distribution range. These findings lead to the hypothesis that I. superba does not exhibit rhizobia specificity at the intrageneric level. Testing of this hypothesis through analysis of its nodulation capability on soils from outside its distribution range is recommended. The fourth chapter of the thesis determined the extent of horizontal gene transfer among rhizobial genera in the Core Cape Subregion (CCR) of South Africa and reconstructed the ancestral symbionts of the legumes. Phylogenies of two chromosomal genes (16S rRNA and recA) and one nodulation gene (nodA) of rhizobia, isolated from diverse legumes in the CCR, were reconstructed using Bayesian and Maximum Likelihood techniques. A cophylogenetic analysis was used to test for congruence between the chromosomal and the nodA phylogenies. Five genera of rhizobia (Bradyrhizobium, Burkholderia, Ensifer, Mesorhizobium and Rhizobium) were studied. A phylogeny of the legumes was reconstructed from matK and rbcL DNA sequences and it was used to reconstruct their ancestral rhizobia, using Bayesian methods. The chromosomal phylogeny of the rhizobia was mostly incongruent with that of nodA, indicating potential horizontal inheritance of the latter. The nodA genes of Burkholderia, Mesorhizobium and Rhizobium had different evolutionary histories from their counterparts in other parts of the globe. Burkholderia was reconstructed as the ancestral symbionts of the CCR legumes. Evidence of co-diversification between the legumes and their symbionts was observed and this highlights a potential role of the legume-rhizobia interaction to the high diversity of legumes in the CCR. Finally, the availability of compatible rhizobia and their competitive ability are discussed as possible drivers for the lack of shared legumes between the CCR’s Fynbos biome and the Kwongan of Australia. Overall, the study shows that edaphic factors and biotic interactions (rhizobia) have significant influence on the distribution of legumes in the Cape Peninsula and the larger Core Cape Subregion of southern Africa. These findings are consistent with the theory that edaphic factors and biotic interactions have a strong influence on species distributions at local and site spatial scales.

Information and communication technologies have accompanied our everyday life for years. A steadily increasing number of computers, cameras, mobile devices, etc. generate more and more data, but at the same time we realize that the data can only partially be analyzed with classical approaches. The research and development of methods based on artificial intelligence (AI) made enormous progress in the area of interpretability of data in recent years. With growing experience, both, the potential and limitations of these new technologies are increasingly better understood. Typically, AI approaches start with the data from which information and directions for action are derived. However, the circumstances under which such data are collected and how they change over time are rarely considered. A closer look at the sensors and their physical properties within AI approaches will lead to more robust and widely applicable algorithms. This holistic approach which considers entire signal chains from the origin to a data product, "Sensor AI", is a highly relevant topic with great potential. It will play a decisive role in autonomous driving as well as in areas of automated production, predictive maintenance or space research. The goal of this white paper is to establish "Sensor AI" as a dedicated research topic. We want to exchange knowledge on the current state-of-the-art on Sensor AI, to identify synergies among research groups and thus boost the collaboration in this key technology for science and industry. Comment: 4 pages. 1st Workshop on Sensor Artificial Intelligence, Apr. 2020, Berlin, Germany

The current development of biodiversity indicators adopted as common in the North East Atlantic (Under OSPAR Regional Sea Convention) is missing some elements necessary for their application as food-web indicators. The Mean Trophic Level (MTL) indicator is based on species biomass and their trophic level (TL). These metrics are commonly used in the food-web holistic approach of interactions in an ecosystem. Species TL, giving the position of an organism in the food web, is influenced by spatiotemporal variability and ontogeny of species. MTL is also shaped by the species biomasses and their data source (i.e. landings or survey data). The aim of the present study was to propose a methodology (1) considering a better regionalisation of the indicator (i.e. using local TL estimations and ecosystem survey data), (2) looking at the MTL sensitivity regarding ecosystem species and compartments and (3) discussing the food web approach of the indicator. Different scenarios were thus tested on MTL indicator with EVHOE survey data (i) using various data sources of TL and (ii) applying several cut-offs to focus on different compartments in the ecosystem. Species influence on each scenario was also investigated. Two species were found to be highly influencing the MTL indicator trend. Capros aper, a low TL species catching the bottom up effect in the food-web, was strongly acting on MTL when considering all species in the ecosystem. Meanwhile, Merluccius merluccius was driving the indicator when low trophic level species were cut-off. This high predator reflected more the top down effect on the ecosystem. This work concluded the need to assess the MTL indicator using three TL cut-offs (TL= 2, 3.25 and 4) to capture a holistic view of changes in the ecosystem. Furthermore, scientific surveys and local estimations of TL are crucial in order to reduce uncertainty around the MTL estimation.

The problem: For protected areas to remain relevant, we need to understand their impact on a wide set of conservation objectives and environmental outcomes. We also need to evaluate how this influence relates to the socio-ecological environment within which they occur. This is a complex endeavour requiring a pluralistic approach, which draws on a wide range of interdisciplinary fields. Research question: This thesis addresses the following question: What effects do mountain protected areas have on ecosystem services over time and how does this influence relate to broader socio-economic and ecological drivers of landscape change? Aim and objectives: I use a pluralistic, socio-ecological framing to assess the impact of ~40 years of mountain protection, drawing on comparisons of ~30 and ~40 years before and after protection respectively, with an adjacent area of similar terrain informing scenarios of counterfactual conditions. I also investigate what types of values (economic and intrinsic) are important when determining the impact of mountain protected areas. Thesis approach and methods: I operationalise the concepts of socio-ecological systems, ecosystem services, land use transitions and counterfactuals to investigate socio-ecological change and how it relates to protected area impact in the Groot Winterhoek, a mountain catchment in the south-western Cape of South Africa. This mountain catchment is important for regional water supplies for agricultural and domestic uses and falls in the Cape Floristic Region, a global biodiversity hotspot. It is comprised of privately owned mountain wildlands and a wilderness-protected area, known as the Groot Winterhoek Wilderness Area, established in 1978 (gazetted in 1985) which forms part of the Cape Floristic Region World Heritage Site. I combine methods from social science, ecology, environmental geography, geomatics and hydrology to understand the history of land use and cover (land use/cover) and associated ecosystem service trade-offs, how they are perceived by landowners as well as their wider impact on the region. Specifically, I assess the impact of protection on land use/cover, vegetation, fire and water flows over the last ~50 years, by comparing and contextualising results of change within the protected area to alternative scenarios of “no protection” (the counterfactual conditions). Vegetation and land use/cover change inside the protected area were determined respectively using 72 repeat terrestrial photographs and vegetation surveys, and an analysis of orthorectified aerial imagery. Methods used to construct the counterfactual scenarios of mechanisms (e.g. changes in land use/cover) that would likely drive vegetation changes inside the protected area included: i) 60 repeat surveys and in-depth interviews with landowners adjacent or proximal to the protected area owning unprotected land of similar terrain to the protected area; and ii) land use/cover change analysis of orthorectified aerial imagery of adjacent unprotected land of similar terrain before and after protected area establishment. 4 This latter information was used to understand the role of the protected area in driving vegetation changes inside the protected area. Social, biophysical and remote sensing results were directly used to parameterise land use/cover components of a hydrological model to determine the influence of protection on water flows. Specifically, water flows were simulated for the current state of the environment inside the protected area as well as for several counterfactual scenarios i.e. the alternative land use/cover scenarios of “no protection”. These counterfactual scenarios included land use/cover at two-time steps of ~30 and ~8 years before protection and one-time step ~40 years after protection both inside and outside the protected area. Results: Long-term change in ecosystem service use outside the protected area on privately owned land of similar terrain to inside the protected area (Section 3): Over the last ~50 years, outside the protected area, there was a shift from livestock-based, subsistence agriculture and small-scale farming to a diversified set of ecosystem service uses. The combined area of grazing and wildflower harvesting declined by 39%, while the number of landowners using the mountains for personal nature-based recreation and ecotourism increased by 61% and 23% respectively. Agriculture intensified in suitable areas of mountain land with the number of landowners cultivating land increasing by 20%. Exogenous socioeconomic drivers associated with globalisation and economic growth were important causal mechanisms of land use change. Landowners valued mountain protection for intrinsic and non-use reasons (73-80% of landowners), including existence, bequest and option values, as well as for the indirect use of water supply (72% of landowners) in comparison with direct use reasons such as spiritual/cultural experiences and nature-based recreation inside the protected area (18 and 50% of landowners respectively). Personal, nature-based recreation outside the wilderness-protected area was associated with valuing the protection of mountain land for intrinsic and non-use reasons. Long-term vegetation change inside the protected area and plausible mechanisms driving vegetation change (Section 4): Inside the mountain protected area, fynbos vegetation cover increased on average between 11 and 30% and there were significant declines in bare ground and rock cover. In 5 accumulation and fire intensities. However, these latter changes in land use/cover also occurred outside the protected area (see results summarised for Section 3 above and Section 4 below) and therefore cannot be attributed to protected area establishment. Land use/cover and the influence on water flows inside the protected area compared to counterfactual scenarios of no protection (Section 5): Declines in grazing and changes to the fire regimes occurred regardless of the protected area boundaries. In the past, there was a high frequency of small, low intensity fires across the landscape, both inside and outside the protected area. More recently, fires have been actively suppressed and this resultsin the build-up of biomass and the development of extensive, high intensity fires which, under suitable conditions, burn large expanses of the mountain catchment. Hydrological modelling showed that a high intensity burning regime negatively affected streamflow regardless of protected area boundaries. Streamflow increased by more than 80% under high flow conditions and decreased by more than 40% under low flow conditions relative to an unburnt ‘natural’ scenario. Over the last 50 years there has also been a substantial increase in dams, buildings and roads and minor increases in cultivation outside the protected area. This has been avoided inside the protected area where these land use/cover classes declined. If the increase in these land use/cover types observed outside the protected area occurred inside the protected area this would have resulted in reductions in daily streamflow leaving the protected portion of the catchment. For example, outside the protected area reductions of 8% to 25% of streamflow were observed during mid and low flow conditions respectively, particularly during dry years, in comparison to a ‘natural’ scenario. In contrast, inside the protected area streamflow recovered from past conditions to more closely resemble the natural flow conditions of the catchment. Therefore, had the protected area not been established there would have been losses in streamflow from the catchment as well as an increase in the degree of fragmentation within this mountain area. However, with increased water storage and fragmentation outside the protected area has also come increased socio-economic opportunities such as employment and local opportunities for ecotourism and sustainable agriculture e.g. indigenous cut flows. This highlights the importance of maintaining various forms of land management systems (multifunctional landscapes) within mountain ecosystems but also the need to understand the sustainability of different land management system types. Determining appropriate land management systems for mountain areas should be based on a full understanding of the impacts on ecosystem service benefits and costs at local and regional levels between social groups both spatially and temporally. Broader significance: This thesis contributes to the conservation literature on two main fronts. Firstly, it contributes conceptually and theoretically to understanding the dynamics of ecosystem services in relation to mountain protection. Secondly, it contributes methodologically by using an inclusive, trans- and interdisciplinary research approach for evidence-based conservation at a place-based and landscape level. The study provides a case 6 study example of the positive impact that mountain protection has on water-related ecosystem services, notably by maintaining streamflow throughout high to low flow periods and during dry years. It also provides clear evidence that ecosystem service trade-offs do not remain constant over time and shows that intrinsic and non-use values are required when describing the importance of mountain protected areas. In terms of understanding the impact that protected areas have in mountain regions, the research shows that complex processes are at play that extend beyond the boundaries of a specific protected area in both time and space. Interactions between global and local drivers were found to be prominent causal mechanisms of socio-ecological change and ultimately determined the influence of mountain-protection on land use/cover, fire, vegetation and water-related ecosystem services. The thesis emphasises that counterfactual framings are necessary to understand and attribute the impacts of protected areas on environmental outcomes, however pluralism and socio-ecological approaches are critical to determine plausible counterfactual conditions. This thesis focused only on landowners adjacent and proximal to the protected area owning the majority of mountain catchment land of similar terrain. It is likely that multiple socioeconomic trade-offs have occurred between different social groups and generations at both local and regional levels. Understanding how the disadvantages and benefits of the impacts of protected areas are apportioned across the landscape and temporally is an aspect that requires future research. Central to this would be to fully consider how human well-being is influenced both upstream and downstream, including at regional levels, and between social groups and across generations. Considering the impact of protected areas on the full range of ecosystem services and linking this to societal preferences and perceptions should be incorporated into the overall goal of developing an evidence base for conservation. This is because it is both scientific evidence and societal change that can determine protected area persistence and thus long-term protected area impact.

The works focus on the identification of industrial robots that belongs to the field of the identification of continuous-time inverse dynamic models in closed loop. First, a generic instrumental approach relevant for the identification of rigid industrial robots is proposed. The set of instruments is the inverse dynamic model constructed from simulated data calculated from the simulation of the direct dynamic model. This algorithm termed the IDIM-IV method validates the inverse and direct dynamic models simultaneously, improves the noise immunity of estimates with respect to corrupted data in the observation matrix and has a rapid convergence. This new approach is experimentally validated and compared with other standard methods. Then, a statistical test able to assess the validity of the set of instruments as well as the consistency of the least-squares estimates is presented. This test is based on the use of the Two-Stage-Least-Squares method and the regressed Durbin-Wu-Hausman test that are commonly used in econometrics. Finally, the perspectives that the IDIM-IV method can offer to the communities of robotics and automatic control are enlightened Ce manuscrit résume les travaux menés sur l'identification des robots industriels conduits à l'ONERA. Dans le premier chapitre, les méthodes usuelles de modélisation et d'identification appliquées aux robots industriels rigides sont présentées. Le deuxième chapitre introduit une nouvelle méthode d'identification basée sur l'utilisation des variables instrumentales alors que le troisième chapitre présente un test statistique capable de valider la construction des instruments. Enfin, dans un quatrième chapitre, les perspectives offerts par ces nouvelles méthodes sont introduites.

Daniel Ricard et Raymond Woessner (dirs.), Les espaces ruraux en France. coll. « Clefs concours », Neuilly-sur-Seine, Atlande

International audience

International audience