Sheet n°255 - December 2006
esertification, erosion
and human activities
are threatening many plant
species in Morocco. In the
forests of the High Atlas,
reforestation with cypress is
one of the priorities of the
Moroccan government’s environmental management strategy. A research team involving Cadi Ayyad University
of Marrakech, the High Atlas
Regional Forestry Directorate
and IRD researchers (1) commissioned by the government, studied an ecological
strategy for restoring vegetation in this area. The investigations focused on interactions between cypress trees,
the pioneer plants–lavender
and thyme–and mycorrhizal
soil fungi with which these
different species associate. While the presence of
mycorrhizal fungi improved
the nutrition and growth of
young cypress, the pioneer
plants provided the favourable conditions for their proper development: they created resource islands, where
fertility is high, in arid tracts
of land and encouraged the
proliferation of fungi, which
all together reinforces efforts
to control soil erosion and
desertification.
© L. Ouahmane/ Université
Cadi Ayyad, Marrakech, Maroc
D
Moroccan High Atlas:
cypress replanting unsuccessful without dual
cultivation with lavender or mycorrhizal fungi
Plantation of Cupressus atlantica, cypress of Atlas (Idni station, Moroccan Hight Atlas).
Foreground : lavander, pioneer plant and "nurse" of the young cypress
Desertification, erosion and human activities are
threatening many plant species in Morocco. In the
forests of the High Atlas, reforestation with cypress is
one of the priorities of the Moroccan government’s
environmental management strategy. A research
team involving Cadi Ayyad University of Marrakech,
the High Atlas Regional Forestry Directorate and IRD
researchers (1) commissioned by the government,
studied an ecological strategy for restoring vegetation
in this area. The investigations focused on interactions
between cypress trees, the pioneer plants–lavender
and thyme–and mycorrhizal soil fungi with which
these different species associate. While the presence
of mycorrhizal fungi improved the nutrition and growth
of young cypress, the pioneer plants provided the
favourable conditions for their proper development:
they created resource islands, where fertility is high,
in arid tracts of land and encouraged the proliferation
of fungi, which all together reinforces efforts to control
soil erosion and desertification.
Morocco possesses a rich and varied flora,
owing partly to its great diversity of relief and landscapes. However, advancing erosion and processes
of desertification, combined with the development of
human activities, are damaging this biodiversity. 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
>>
Institut de recherche pour le développement - 213, rue La Fayette - F-75480 Paris cedex 10 - France - www.ird.fr
CONTACTS :
ROBIN DUPONNOIS
IRD UMR 040 LSTM (Laboratoire
des symbioses tropicales et
méditerranéennes) IRD/Cirad/
ENSAM, Laboratoire Commun de
Microbiologie IRD/ISRA/UCAD du
campus Agronomique de Dakar,
Sénégal.
Tél. : (221) 849 33 22.
robin.duponnois@ird.sn
MOHAMED HAFIDI
Faculté des sciences Semlalia,
Université Cadi Ayyad,
Marrakech, Maroc
Tel : (212) (0)24 43 76 65
hafidi@ucam.ac.ma
LAHCEN OUAHMANE
Centre Régional de Recherche
Forestière Marrakech, Maroc.
Tel : (212) (0)24 68 72 93 36
Faculté des sciences Semlalia,
Université Cadi Ayyad,
Marrakech, Maroc. Tél : (212)
(0)24 43 76 65
l.ouahmane@ucam.ac.ma
PRESS OFFICE:
+33 1 48 03 75 19 ;
presse@paris.ird.fr
INDIGO BASE, IRD PICTURE LIBRARY
+33 1 48 03 78 99 ;
indigo@paris.ird.fr
IRD AUDIOVISUEL
+33 (0)1 48 02 56 24 ;
audiovisuel@bondy.ird.fr
www.audiovisuel.ird.fr/
REFERENCES:
LAHCEN OUAHMANE, MOHAMED
HAFIDI, CHRISTIAN PLENCHETTE,
MARIJA KISA, ALI BOUMEZZOUGH,
JEAN THIOULOUSE, ROBIN
DUPONNOIS – Lavendula species as accompanying plants
in Cupressus replanting strategies: Effect on plant growth,
mycorrhizal soil infectivity
and soil microbial catabolic
diversity, Applied Soil Ecology,
2006, 34: 190-199.
DOI: 10.1016/
j.apsoil.200602.002
LAHCEN OUAHMANE, ROBIN
DUPONNOIS, MOHAMED
HAFIDI, MARIJA KISA, ALI
BOUMEZZOUCH, J. THIOULOUSE
AND C. PLENCHETTE – Some
Mediterranean plant species
(Lavandula spp. and Thymus
satureioides) act as potential
“plant nurses” for the early
growth of Cupressus atlantica,
Plant Ecology, 2006, 185 (1):
123-134.
DOI: 10.1007/s11258-0059089-9
KEY WORDS
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
Cypress saplings between
young lavender
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.
(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-Signoret - IRD
Translation : Nicholas Flay
© L. Ouahmane/ Université Cadi Ayyad,
Marrakech, Maroc
Sheet n°255 - December 2006
For futher information
CYPRESS, PIONEER PLANTS,
LAVENDER, MYCORRHIZA,
REVEGETATION, DESERTIFICATION,
MOROCCO.
Marie Guillaume - Signoret, coordinatrice
Délégation à l’information et à la communication
Tél. : +33(0)1 48 03 76 07 - fax : +33(0)1 40 36 24 55 - fichesactu@paris.ird.fr