One of the representative species of this flora, the cypress Cupressus atlantica, is experiencing year by year a decrease in its biomass production and the surface areas it occupies. This species contributes to efforts to control erosion and degradation of forest soils. But it is highly sought after by local communities particularly for the quality of its wood. In addition, the young shoots are subjected to overgrazing (by sheep) which hinders the species’ natural regeneration. Replanting operations have been undertaken, but have proved largely unsuccessful, with nearly 70 % of the young saplings planted dying after the first year.
To counter the threat hanging over this species, a research programme was set up in 2003, jointly between the Cadi Ayyad University of Marrakech, the High Atlas Regional Forestry Directorate and scientists from IRD research unit UR 040 (1). The IRD researchers proposed an original ecological approach, founded on the study of interactions between the cypress, the shrubby plants–lavender and thyme–associated with them and the soil microflora, in order to define new practices for cypress replanting schemes in the Moroccan Atlas.
Cypress develops symbiotically with soil micro-fungi, arbuscular mycorrhizal fungi (2). This association yields mutual benefits, the plant providing sugars for the fungi which in return helps provide the tree’s supply of water and mineral salts, mainly of nitrogen and phosphorus. In controlled mycorrhization glasshouse experiments, the researchers inoculated strains of these fungi, sampled from the study zones in the Moroccan High Atlas, into young nursery plants. There resulted a distinct improvement in the development of these young cypress with inoculated mycorrhizal fungi, which had a higher level of minerals in their leaves (21 % more phosphorus, in particular). Other experiments, conducted in the field, confirmed this result: the fungi favour better nutrition for the young cypress which enables them to build up greater resistance to transplantation-linked hydric stress for when they are adult. Although it is effective, this plant-by-plant inoculation technique remains cumbersome and costly, which limits its large-scale use.
In the cypress stands of the Moroccan High Atlas, several species of lavender and thyme are associated with the trees. These pioneer species, which form sparse clumps of vegetation, are the first to colonize the stony eroded soils of these arid and semi-arid ecosystems. Soil analyses revealed that these species generate islands of fertility, resource islands, rich in nitrogen and phosphorus, as well as in mycorrhizal fungi with which these plants also live in symbiosis. However, what role do they play in the development of young planted cypress saplings?
Lavender and cypress grown together and inoculated with mycorrhizal fungi under glass showed significantly higher growth than when they were cultivated and developed separately. Moreover, the concentration of propagules (3) appeared greater around the lavender roots than around those of cypress and, even more so, than around bare soil (244.5, 179.7 and 7.82 for 100 g of dry soil respectively). Lavender therefore favours the proliferation of mycorrhizal fungi and of their mycelium in the soil. As it reproduces, this “nurse” plant multiplies the number of resource islands generated, which eventually increases the fertility of the whole of the terrain involved. It therefore creates conditions that encourage growth of the planted cypress, stabilizing the soil as it does so by its roots.
Increased understanding of the process of natural regeneration of cypress trees has allowed the application of a new method of replanting of this species in the Moroccan High Atlas. In the sites that must be re-wooded, bands of lavender were planted in strips of earth built up perpendicularly to the slope so as to retain water. The cypress saplings were planted the following year. The first results confirm the beneficial role lavender has on these young plantations: their mortality after one year proves to be very low and soil erosion remains limited.
Research investigations were also conducted on other associations of species, such as cork oak and cysts, or again thujas and lavender. The latter are the subject of a trial conducted by the Rabat Regional Forestry Directorate in areas undergoing reforestation in the North of Morocco.
Marie Guillaume-Signoret - IRD
(1)These investigations were conducted by the IRD, in conjunction with and at the request of Moroccan partners, jointly with the ‘Laboratoire Ecologie and Environnement’ of the Semlalia Faculty of Sciences (Université Cadi Ayyad). The IRD team (UR 040, led by R. Duponnois) belongs to the ‘Laboratoire des symbioses tropicales and méditerranéennes (LSTM)’, UMR 113, which also involves CIRAD, INRA, Agro-Montpellier and the University of Montpellier II. This work takes up the thesis of Lahcen Ouahmane, produced in the team of Prof. Mohamed Hafidi in conjunction with R. Duponnois and which is due to be judged in February 2007 at Marrakech.
(2)Arbuscules are fungal structures that symbiotic fungi form inside the root cells of most cultivated plants and many forest tree species. They are the site of nutritional exchanges between the two partners in the symbiosis. The fungi moreover develop a vast network of mycelial threads in the ground, which acts as a vital interface between the soil and the plant.
(3)In the fungi, these are the groups, of cells that initiate the development of the tubular mycelial threads (a process of asexual reproduction).
Marie Guillaume | alfa
Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen
A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy