沙漠研究 19-1, 165- 167 (2009 )Journal of Arid Land Studies“Desert Technology IX ”
Refereed Paper

Natural Vegetation Cover Dynamic under Climatic Drought and Human
Disturbance in the Matmata Mountains, Southern Tunisia
Farah BEN SALEM*1, Mohamed TARHOUNI1, Azaiez OULED BELGACEM1, Mohamed NEFFATI1
Abstract: This study deals with the assessment of the effects of climatic drought and humandisturbance on the natural vegetation cover in the arid zone of Tunisia (Matmata Mountains).
Plant cover and density were assessed and monitored during two seasons (fall 2005 and spring2006) using the quadrat-point method in four sites (stations) which differ by their disturbancedegree. Main results show that the plant cover is mainly influenced by the human activities.
The highest plant density was recorded during the spring.
Keywords: Climatic drought, Desertification, Human disturbance, Plant density, Vegetation cover

1. Introduction
Desertification has been considered, since few decades, the principal environmental problem in the aridzone of Tunisia (Le Houérou, 1995, 2001). This zone is characterised by recurrent climatic droughts
aggravated by the extension of various human activities such as overgrazing and annual cropping (OuledBelgacem et al., 2006). The drought results from the variability and unpredictability of rains and thesuccession. The impact of climatic drought is more intense in the ecosystems subjected to humandisturbance (Teague et al., 2004). This study aims at monitoring and assessment of some ecologicalindicators (total vegetation cover, plant density) under climatic drought and human disturbance in theMatmata Mountains of southern Tunisia.
2. Materials and Methods
The plant cover and total plant density were monitored and assessed during two seasons (fall 2005 andspring 2006). The annual rainfall was about 176 and 238 mm in the nearer meteorological stations(Matmata and Dkhilet Toujane respectively) of our studied sites. This study carries by the use of thequadrat-point method (Daget and Poissonnet, 1971) in four sites (stations) which differ by their location,altitude, soil substratum and disturbance degree. The first site is characterised by loamy substratum withhigh density of Stipa tenacissima L., Rosmarinus officinalis L., and Genista microcephala Coss. The
second site is dominated by Stipa tenacissima on loamy substratum. The third site is dominated by Stipa
tenacissima and Rosmarinus officinalis on gypsum substratum. The fourth site is dominated by Stipa
tenacissima and Gymnocarpos decander Forsk on calcaro-gypsum substratum. The main studied
indicators are: i) the total vegetation cover (TVC), determined as TVC = (n/N)*100, with n: number ofpoints where the vegetation is present and N: total number of sampled points, ii) the total plant density (Dt)and the density of the old and young plants (desiccated or alive). The plant density is measured in ten 20 m2
area sampling units. The obtained data was analysed by several statistical tests (One-way ANOVA, Tukey
LSD test and dependant t test) using the SPSS 11.5 software (SPSS Inc, 2002).
3. Results and Discussion
As shown by the Figure 1, the plant cover (TVC) is significantly different between the four studiedstations. Plant cover is also affected by drought. The difference between the dry and the rainy season issignificant (p < 0.05). This difference is explained by the abundance of annual plants when the climaticconditions are appropriate.
The mean total plant density (Dt) determined in the four studied stations (Fig. 2) shows that thisdescriptor varies highly between stations and seasons. The evolution of plant density in station 1 gives amore reliable idea on the tendency of establishment or the disappearance of the plant species and permits toevaluate the aptitude of regeneration of the ecosystem (Floret, 1988). When plant density is important,the soil particles are fixed and enhance water infiltration which provokes seed emergency and plantdevelopment.
1Range Ecology Laboratory. Institut des Régions Arides – 4119 Médenine - Tunisia. *Corresponding Author

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TVC80706050403020100
Fall 2005

Spr ing 2006

Station 1

Fall 2005

Spr ing 2006

Fall 2005

Station 2Spring 2006

Fall 2005

Station 3

Spr ing 2006

Station 4

Fig. 1. Total vegetation cover (TVC %) during the fall (2005) and the spring (2006) seasons in the four studiedstations.
Dt100
9080706050403020100
Fall 2005

Spr ing 2006

Station 1

Fall 2005

Spring 2006

Fall 2005

Station 2Spring 2006

Fall 2005

Station 3

Spring 2006

Station 4

Fig. 2. Variation of total plant density (Dt in plant m-2) during the fall (2005) and the spring (2006) seasons inthe four studied stations.
Table 1. Variation of plant density in the four studied stations (in plant m-2) (DY: dried young plant; GY: Green
young plant; DA: dried adult plant; GA: green adult).

GYGA
DYDAStation 1
FallSpring
2005
2006
3.48±0.95
78.11±3.56
11.47±0.1313.69±1.47
0.01±0.002
0.01±0.001
1.48±0.07
1.28±0.12

Station 2
FallSpring
2005
2006
0.83±0.12
81.97±2.97
1.44±0.38
0.84±0.09
0.01±0.006
01.12±0.03
0.95±0.02

Station 3
FallSpring
2005
2006
0.85±0.05
62.2±4.21
2.05±0.53
0.86±0.1100
1.41±0.31
1.18±0.18

Station 4FallSpring
2005
2006
1.77±0.75
45.95±2.61
1.93±0.07
1.92±0.26
0.01±0.007
0.07±0.01
1.2±0.01
1.14±0.09

Table 1 shows that the highest density of the dead tufts was recorded for the adult one (DA) during
the two seasons for all stations. Green tufts of adult or young plants dominate in spring. All theseresults show that the ecosystems of the Matmata Mountains are more resilient and conserve a higher
regeneration capacity after drought periods (Ben Salem et al., 2007).
4. Conclusion
The climatic drought and human disturbance effects on the natural vegetation cover in the four studied
stations of the Matmata mountains are determined following many indicators. The main results are: i) theplant cover is influenced by climatic drought, ii) in the two seasons the establishment of plants is more
important in station 1 and iii) the majority of the old and vigorous plants seem to be more vulnerable todrought than the young individuals.

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References
Ben Salem F., Tarhouni M., Ouled Belgacem A., Neffati M. (2007): Impact of drought on plant cover dynamics in two natural areas ofSouthern Tunisia. J. Biol. Scien., 7(8): 1539-1544.
Daget P., Poissonnet J. (1971): A method of phytologic analysis of the meadows. Criteria of application. Agrono. An., 22(1): 5-41.
Floret Ch. (1988): Methods of measurement of the pastoral vegetation: Pastoralism and Development.CIHEAM, Montpellier, France;
95 p.
Le Houérou H.N. (1995): Bioclimatologie et biogéographie des steppes arides du Nord de l’Afrique. Diversité biologique,développement durable et désertisation. CIHEAM Options Méditerranéennes, Série B, N°10, Montpellier, France, 396 p.
Le Houérou H.N. (2001): Biogeography of the arid steppeland north of the Sahara. Journal of Arid Environments. 48: 103-128.
Ouled Belgacem A., Chaieb M., Neffati M., Tiedeman J. (2006): Response of Stipa lagascae R. & Sch. to protection under arid
condition of southern Tunisia . Pak. J. of Biol. Scien., 9(3):465-469.
SPSS (2002): SPSS 11.5 for Windows Update, SPSS Inc, U.S.A.
Teague W.R., Dowhower S.L., Waggoner J.A. (2004): Drought and grazing patch dynamics under different grazing management. J.
Arid Envir., 58: 97-117.