Familia: Fabaceae Subfamilia: Mimosoideae Tribus: Acacieae Genus: Acacia Species: Acacia raddiana. Name. Acacia raddiana Savi. References. Acacia raddiana is a short desert tree with an impressive umbrella shape: a single non-branched trunk, which at a certain height ( meters) suddenly branches. Request PDF on ResearchGate | On Jan 1, , E. Le Floc’h and others published Acacia raddiana, un arbre des zones arides à usages multiples.
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The findings concerning the quasi-irreversible degradation of ecosystems north and south of the Sahara are widely accepted. The causes are to be found on the one hand in unfavourable climatic changes, and on the other, in increasing human activity. Rehabilitation of degraded land is required if human activities are to continue in a rural environment, since the spontaneous vegetation in these regions provides essential food for animal herds, it is the main source of energy, and represents stocks for the re-formation of agro-forestry systems.
Large-scale reforestation programmes have already been implemented to stop land degradation. However these have quite frequently ended in failure, due to the incapacity of the introduced exotic species to adapt to drought and to the low level of fertility of the areas in which they were introduced.
In addition these ‘artificially constructed’ systems – which are neither sustainable nor reproducible – also create management problems. Faced with these failures, research programmes for the rehabilitation of land in arid areas turned their attention towards the introduction of complex systems multi-story communities aimed at achieving improved stability and increased resilience in order to reduce the risks that threaten production in pastoral and agro-forestry areas.
File:Acacia raddiana in Bouhedma – – Wikimedia Commons
Recourse to local species that are usually better adapted to the local environment and well known by the local population has become indispensable. Among these species, leguminous trees and herbaceous species are of particular interest thanks to their double capacity to reduce atmospheric carbon dioxide and atmospheric nitrogen, which makes them models of choice in programmes for the rehabilitation of ecosystems and sustainable development.
However the implementation of these options runs into difficulties on the one hand due to lack of knowledge of the species, and, on the other, the need to identify, characterise, and model the complex dynamic interactions within the ecosystems concerned.
It also involves multidisciplinary research. The model described in this book is Acacia tortilis subsp.
Researchers in different special fields arising from ecology, eco-physiology, genetics, microbiology, entomology and raddizna combined forces to clarify the taxonomy and identify the geographical distribution of this species, to analyse the diversity both of the plant host and of the associated micro-organisms, to characterise its mode of functioning and its interactions in the natural environment in response to water and nitrogen factors, and thus to bring together the elements required for its use in rehabilitation actions.
Before suggesting possible future research topics that arise from the results of the studies described in this book, there follows a summary of the main results obtained. It is characterized by ecological plasticity, and colonises regions receiving between 50 and 1 mm of annual rainfall and located at altitudes of up to 2 m.
The populations of acacua taxon display considerable genetic variability partly explained by polyploidy. The plant can be classified among species with high nitrogen fixing potential and low yield.
The species is widely used by local populations as for medicinal purposes, as fodder, as fuel wood, and as charcoal thanks to the high calorific power of its wood. It is used by craftsmen to make a range of gaddiana and utensils.
It is also used to tan hides and the gum it produces eaten. It is also used to stabilise and fertilise the soil. This plant thus plays an important role in rural economy. The results of the studies underline Acacia raddiana’s faddiana resistance to drought, it survives, grows raddianq develops in its preferred areas despite evaporative demand and limited rainfall.
Phenology although displaying considerable inter-site and intra-population variability, appears at least in Northern Senegal, to be closely linked with soil water reserves, with the exception of the installation of foliage, which apparently results from adjustment of the osmotic balance.
Studies concerning the taxonomic diversity and the symbiotic properties of rhizobia nodulating Acacia raddiana revealed the wide taxonomic diversity of isolates, which contrasts with the marked homogeneity of the main symbiotic characteristics and with the structure of the ‘Nod factors’, these being good indicators of the nodulation potential of a given rhizobium.
In the legume-bacteria symbiosis, the factor likely to impede nodulation and nitrogen fixation is generally not the absence of efficient bacterial strains, but one or more ecological factors that limit their efficiency. This knowledge led to determining the raddian to thermal, saline and water stress displayed by strains of nodule forming bacteria isolated in the soil in Tunisia and Senegal. As a whole, while displaying equal water potential, the strains were more wcacia to water stress than to salinity.
The recognized high nitrogen-fixing potential of this acacua is linked with the presence of numerous nodules during the rainy season, located raddianz the trunk m and between 25 and 75 cm in depth in natural conditions. Mycorrhizian infection is considerably reduced in eroded environments.
File:Acacia raddiana in Bouhedma – Fruits.jpg
Despite the generally low level of biochemical and micro-biological activity in the soils linked to both arid conditions and edaphic depletion low organic matter content, low level of nutrients, water deficit, etcalmost all the parameters monitored in the soils were modified by the presence of the Acacia raddiana root system, which thus demonstrated its rhizospheric effect.
This effect varies as a function of a number of parameters rqddiana as distance from the trunk, rraddiana age of the population, and nutritional factors at the site. These results highlight raddina primary role of the tree in improving nutritional conditions by forming radidana of fertility in an arid or semi-arid environment.
The tree – in our case Acacia raddiana – favours the development of the herbaceous layer, which in turn, results in an increase in the flora richness, and in the production and storage of bio-elements in the under-story herbaceous layer. The knowledge that has been accumulated on seed pests, germination ability and production techniques for seedlings, and plantation maintenance, makes the use of this taxon possible in plantation systems that require high or low levels of technical expertise.
Our results show that there is no apparent link between the taxonomic position and the geographic acacua of the strains of rhizobia that incidentally display marked homogeneity in their main symbiotic characteristics. However, it should be noted that the Senegalese strains appear to be more resistant to salinity.
It also became apparent that mycorrhizal infection of the provenances of Acacia raddiana north of south were similar. The metabolic activity of the micro-organisms in Tunisia is however, considerably higher than in Senegal.
With respect to the moisture balance north and south of the Sahara, although the availability of water is limited in time, it was greater in the surface horizons at the Tunisian site, which favours the development of superficial roots. This specific stratification of soil water stocks helps explain why the phenological cycle matches the rainy season in Senegal.
In Tunisia, Acacia raddiana respects a tropical rhythm, with the major part of its cycle occurring in summer. The studies presented in this book naturally do not claim to be exclusive.
Much remains to be done to complete our understanding of this taxon whose diversity, plasticity and multiple adaptations to ecological conditions are remarkable. There follows a brief summary of some of the future research topics suggested by the different contributions.
As far as micro-organisms are concerned, confirmation is needed of the different groups of strains of Rhizobium nodulating Acacia raddiana using phylogenetic raddinaa to determine their taxonomic position and to suggest possible final nomenclature. In another connection, it will be useful to improve our knowledge of the diversity and the ecology of arbuscular mycorrhizial fungi in the soil in order to select the most efficient as innoculum.
The range of seed-eating coleoptera that are parasites of the Acacia raises questions that need answering concerning the trophic and ecological specialization of coleoptera, identification of defence mechanisms used by Acacia, and the characterisation of co-evolution of the insects and the host plant.
With respect to functional aspects, the exact links between transpiration and phonology need to be established, since this relationship will open the way to forecasting transpiration. There is also a growing need to increase the yield of the potential nitrogen fixer on Acacia raddiana by selecting the provenance, and the descendants with a high yield.
The use of clones could considerably acqcia this selection process. It is true that the genetic study of this species is hampered by its polyploidy, which underlines the rwddiana for improvement of genetic models that are suitable for the interpretation of tetrapoloid markers. The contribution of genetics should also be directed towards the dynamics of genetic diversity of this sub-species. Knowledge of the consequences of past and present practices on the current state of genetic diversity should enable improved assessment of its future in the face of disturbances linked to climatic changes and the population increase.
The restoration of populations of Acacia raddiana requires further study of appropriate techniques, either for the replacement of destroyed ecosystems, or for the densification of widely-spaced populations. There are numerous benefits to be had from such plant formations, in particular for the conservation of biodiversity in its widest sense: Evaluation and Outlook by M.