The efforts for cork oak forest management and their effects on soil

Transcription

The efforts for cork oak forest
management and their effects
on soil conservation,
the Sehoul plateau, Rabat
region, Morocco
A. Laouina, M. Aderghal, J. Al Karkouri, M. Antari, M.
Chaker, Y. Laghazi, I. Machmachi, N. Machouri, R.
Nafaa, K. Naïmi, A. Nouira & M. Sfa
Moroccan team of the DESIRE project
UNESCO-GN Chair, FLSH, Univ. Mohammed V, Rabat
Presented by Dr A. Nouira
Introduction
In the Atlantic meseta, human pressure on
forest, made them loose their original
extension and natural characteristics
(modification of the floristic composition)
The traditional use covers both agriculture by
sedentary populations and grazing by nomad
The modern forest management participates in
changing the forest role
The location of forest close to important cities
explains the apparition of new activities
The forest offers multiple uses
Cork exploitation;
Pasture land,
Resource of fire wood.
Regular exploitation and cutting operations are organised
by the forestry administration.
But overgrazing and irregular cutting of fire wood threaten
the forest ecosystem and leads to land degradation.
Due to the proximity of urban agglomerations, the forest is
also visited for leisure. The orientation towards a tourist
function can lead to a complete transformation of the
management rules.
The evolution of cork oak forest, in relation with
degradation processes leads to progressive loss of its
environmental balance plus the reduction of its
economic contribution.
The fragility of the forest is the consequence of the
combination of two main factors,
-i) the fragile environment due to low vegetation cover,
leached soils and water availability;
-ii) human action on the forest environment contributes
to its degradation and the change of its floristic
composition.
Low cover
Loss of biodiversity
Overgrazing
The effects of management actions
To overcome degradation phenomena, cork oak forest
was replaced by newly introduced species (eucalyptus
and pine).
Recently, tendency is to manage the cork oak stands .
The goal of this operation is to guaranty the cork oak
regeneration, to improve cork yield and to reduce land
degradation. This will contributes to overland flow
decrease and infiltration increase.
Superficie
(ha)
%
Dense Cork oak
2223,62
46%
Normal cork oak
999,63
21%
Slightly dense cork oak
729,44
15%
Sparse cork oak
726,35
15%
Mixture of cork oak and secondary essences.
133,83
4812,87
3%
100%
Land cover
Assisted cork oak regeneration
99 ha
Eucalyptus reforestation
543 ha
Pine reforestation
97 ha
Forest (all species and densities) : 8395,42ha, 21,5% of the commune
Evaluation of management practices
1- The Use of radioisotope 137Cs
Sehoul Forest
cropped land
-3,51
2,42
1,47
-2,86
Ref5
Ref11
9,11
Cercle de rayon 10 m -8,03
Cercle de rayon 20 m -11,67
Ref10
Ref7
Ref4
7,45
‐12,39
Ref6
-6,90
Ref12
Ref2
-10,37
Ref1
3,10
Ref3
-1,02
Ref8
Ref9
137Cs
measurements
Soil losses estimated for different sampling points
were ranging from 1,2 to 12,4 t/ha/yr with a mean
erosion of about 6 t/ha/yr. The deposition values were
varying from 1,47 to 9,11 t/ha/an with deposition of
about 4 t/ha/yr.
Cereal parcel
mean erosion : 12 t/ha/yr.
Parcel under cereal/legumes rotation
8 t/ha/an.
Parcel with vine Monoculture
11 t/ha/an.

Cork oak forest shows a less
erosion compared to agricultural fields
3- The hydrologic measurements at the catchment scale
5- The surface measurements

Vegetation cover
Soil moisture
Surface soil parameters
Rain simulation
Measurements in 8 plots and samples inside
various types of forest cover
-regenerated cork oak (protected and not)
-Pine and eucalyptus
-different stages of degradation inside cork
oak cover
Phytomasse
KgMV/ha
Asphodèle
Autres Herbacées
Cistes
Autres Arbustes
8000
Estimation of the phytomass
7000
-soil cover and protection?
6000
-Economic income ?
5000
4000
3000
2000
1000
0
Reg 1.MD
Reg 2.OP
Eu
Pin
CL Dense
CLNormal
CL Clair
CL Epars
Fig,6: La phytomasse totale des herbacées (Asphodèle + Autres herbacées) et des arbustes (Cistes+ Autres arbustes) au
niveau de la forêt de Sehoul (mars-avril 2008)
Herbacée
Recouvrement moyen (%)
100
90
80
Litiére
Sol Nu
70
60
50
40
30
20
10
0
Reg 1.MD Reg 2.OP
Eu
Pin
CL Dense CLNormal CL Clair
Fig.1: Recouvrement moyen des herbacées, de la litière et du sol nu au niveau de la forêt de
Sehoul (mars-avril 2008)
CL Epars
Nombre d'espèce /m2
30
25
20
15
10
5
0
Reg 1.MD Reg 2.OP
Eu
Pin
CL Dense CLNormal CL Clair CL Epars
Fig.7: Biodiversité floristique au niveau de la forêt de Sehoul
(%)
8
7
6
5
4
3
2
1
0
Reg 1.MD
Reg 2.OP
Eu
Pin
CL Dense
CL Clair
CL Epars
Fig.8: Les teneurs d'humidité des sols au niveau des sites d'échantillonnage de la forêt de Sehoul (avril 2008)
Carbone organique (%)
%
Matière organique (%)
Azote total (%)
8
7
6
5
4
3
2
1
0
Reg 1.MD
Reg 2.OP
Eu
Pin
CL Epars
Fig.10 : Fertilité des sol (matière organique, carbone organique et azote total) au
niveau de la forêt de Sehoul
6- Rain simulation, Runoff measurement
Ruissellement cumulé (ml)
7000
6500
6000
Forêt de chêne régénérée de 10 ans
fortement pâturée
5500
5000
Forêt de chêne naturel pâturée
4500
4000
3500
3000
2500
2000
1500
1000
500
0
0
3
6
9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60
Temps (mn)
Infiltration (m m /h)
160
140
Forêt de chêne mise en défens
120
Forêt de chêne ouverte au pâturage
100
80
60
40
20
0
0
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
Temps (mn)
Conclusion
The forest behaviour, compared to other
uses conserves land stability
The choice for forest management, by
cork oak regeneration, with grazing
regulations and protection, represents
the more promising alternative to
remediate the current situation of land
degradation.
It requires a high financial supply and a
real appropriation by the local population.