Allometric relationships for predicting the stem volume of Acer monspessulanum and evaluation of NDVI values to estimate some stand parameters using Sentinel-2 satellite image

The objectives of this work are to evaluate allometric models for predicting stem volume and use NDVI index to estimate stand parameters of Acer monspessulanum, using Sentinel-2 images for the determination of NDVI index. Forty-nine (49) sample plots of 20 x 20 m were used as ground truth data and randomly split into two groups: 70% for fitting data and 30% for data validation. We determined 12 dendrometric characters and the spectral index NDVI for each tree. The heights of the trees varied between 2.2 and 10.8 m and the DBH (Diameter at Breast Height) varied between 0.15 and 1.2 m. The analyzed relationships were between: (i) individual stem volume and dendrometric parameters, (ii) individual tree NDVI and the dendrometric parameters and (iii) individual crown diameter and NDVI. The relationships were evaluated using ten allometric models. The regression study showed that the diameter and the height presented the robust relationship with tree volume in cubic and power models (R2=0.997). Power and cubic equations were also confirmed as good predictors using NDVI. With these models, we can estimate dendrometric parameters and predict tree volume. Keywords: Maple tree, NDVI, allometric model, dendrometric parameters, remote Sensin

Le chêne zéen (Quercus canariensis Willd.) en Tunisie: Écologie, production, état de dégradation et les pratiques d’aménagement

This study is a review paper of species Quercus canariensis, an endemic species of the Ibero-Maghreb localities (Spain, Portugal, Morocco, Algeria, Tunisia). This work will contribute firstly to knowledge of the ecology and production of this species which has undergone a lot of pressure and degradation in recent years in Tunisia and secondly the prospects for the management practices of the species for their protection. This study is carried out with the aim of studying the ecology, production and state of degradation of the species and finally to study the management practices of Quercus canariensis in Tunisia. It is based on research work carried out in Tunisia over 70 years on Quercus canariensis (30 bibliographical references since 1952). In Tunisia, the main zeen oak stands are concentrated in the mountains of Western Kroumirie. The first clear cuts of zeen oak in Tunisia were made between 1883 and 1895 in El Feidja and Ain Draham. Before colonization, the zen oak occupied 100,000 ha in the north-west of Tunisia. In 1970 this area decreased to 40,000 ha, including 10,000 ha in pure stands and 30,000 ha mixed with cork oak. Currently the area of ??zeen oak is estimated at 8,332 ha in pure stand and 13,651 ha mixed with cork oak. The ancient zeen oak trees exceed an age of 330 years. The mean annual growth of zeen oak stands varies between 4 and 8 m3 ha-1yr-1 in middle-aged stands. In this stand, the standing volume is 307.8 m3 ha-1. Total biomass production varies between 211 and 267 Mg ha-1. The zeen oak forest has lost, after 40 years, about 40% of its area. However, new forest species have occupied the landscape since the end of the 1980s, such as the acacia, the Aleppo pine, the eucalyptus, the stone pine and the maritime pine which are now invading the zeen oak ecosystem and oak cork. Today, the zeen oak forest faces continuous progressive and irreversible degradation. Deforestation has prevented natural regeneration, moreover, various diseases and climate change also play a negative role. So we add to this set of factors the absence of forest management, hence silvicultural treatments are necessary for the conservation and enhancement of this noble species which is considered a natural heritage in Tunisia. Keywords: Zeen oak, Geographical distribution, Increase, Production, Silviculture, Management, InterestCette étude est une synthèse bibliographique sur l’espèce Quercus canariensis, essence endémique de l’ensemble ibéro-maghrébin (Espagne, Portugal, Maroc, Algérie, Tunisie). Ce travail va contribuer en premier lieu à la connaissance de l’écologie et la production de cette espèce qui subit beaucoup de pression et de dégradation ces dernières années en Tunisie et en deuxième lieu les perspectives de réhabilitation de l’espèce pour leur protection. L'étude est réalisée dans le but d’étudier l’écologie, la production et état de dégradation de l’espèce et enfin étudier les perspectives de réhabilitation de Quercus canariensis en Tunisie. Elle est basée sur les travaux de recherches qui ont été réalisés en Tunisie sur 70 années sur Quercus canariensis (30 références bibliographiques depuis 1952). En Tunisie, les principaux peuplements de chêne zéen sont concentrés dans les montagnes de Kroumirie occidentale. Les premières coupes rases de chêne zéen en Tunisie sont réalisées entre 1883 et 1895 à El Feidja et d'Ain Draham. Avant la colonisation le chêne zéen a occupé 100 000 ha dans le Nord-Ouest de la Tunisie. En 1970 cette superficie a diminuée à 40 000 ha, dont 10 000 ha en peuplements purs et 30 000 ha en mélange avec le chêne liège. Actuellement la superficie de chêne zéen est estimée à 8332 ha en peuplement pur et 13 651 ha en mélange avec le chêne liège. Les anciens arbres de chêne zéen dépasse un âge de 330 années. L'accroissement moyen annuel des peuplements de chêne zéen varie entre 4 et 8 m3 ha-1an-1 dans les peuplements d'âge moyen. Dans ce peuplement le volume sur pied est de 307,8 m3 ha-1. La production de la biomasse totale varie entre 211 et 267 Mg ha-1. La forêt de chêne zéen a perdu, au bout de 40 ans, environ 40 % de sa superficie. Cependant, des nouvelles espèces forestières ont occupé le paysage dès la fin des années 1980, comme l'acacia, le pin d’alep, l’eucalyptus, le pin pignon et le pin maritime qui envahissent maintenant l’écosystème de chêne zéen et de chêne liège. Aujourd’hui, la forêt de chêne zéen est confrontée à une dégradation progressive et irréversible continue. Le déboisement a empêché la régénération naturelle, en outre, les différentes maladies et les changements climatiques jouent aussi un rôle négatif. Aussi nous ajoutons à cet ensemble de facteurs l’absence de l’aménagement forestier, d’où des traitements sylvicoles sont nécessaires pour la conservation et la valorisation de cette espèce noble qui est considérée comme un patrimoine naturel en Tunisie. Mots-clés : Chêne zéen, Répartition géographique, Accroissement, Production, Sylviculture, Aménagement, Intérê

Effect of climate change on the spatial distribution and cork production of Quercus suber L., the risk of exclusion by the Aleppo pine expansion, and management practices to protect Q. suber habitat: A review

Climate change represents an important challenge for forest management and the silviculture of stands and it is known that climate change will have complex effects on cork oak forest ecosystems. North Africa and the Mediterranean basin are especially vulnerable to climate change. Under the effect of climate change, cork oak will disappear from a large area in the future, and the rest will migrate to higher altitudes and latitudes. This study aimed to evaluate the effect of climate change on the spatial distribution of Quercus suber L. and cork production in the Mediterranean area, and the risk of its exclusion by the Aleppo pine (Pinus halepensis Mill.) expansion. The literature review showed that up to 40% of current environmentally suitable areas for cork oak may be lost by 2070, mainly in northern Africa and the southern Iberian Peninsula. Temperature directly influences atmospheric evaporative demand and should affect cork productivity. Precipitation is the main factor that positively influences cork growth and several authors have confirmed the negative effect of drought on this growth. Currently, cork oak habitats are colonized in several places mainly by the Aleppo pine. Under climate change, Aleppo pine is projected to occupy higher altitude sites and several authors have predicted that current and future global warming will have a positive influence on Aleppo pine growth in wet sites. In the future and under climate change, there is a strong possibility that the Aleppo pine will colonize cork oak habitat. Finally, we proposed management practices to protect cork oak against climate change and Aleppo pine expansion

Essential oils of Origanum vulgare L. subsp glandulosum (Desf.) letswaart from Tunisia: chemical composition and antioxidant activity

BACKGROUND: Characterisation of the essential oils from O. glandulosum collected in three locations of Tunisia, chemical composition and the evaluation of their antioxidant activities were carried out. RESULTS: The essential oils from Origanum vulgare L. subsp. glandulosum (Desf.) letswaart collected from three localities of north Tunisia - Krib, Bargou and Nefza - were obtained in yields of 2.5, 3.0 and 4.6% (v/w), respectively. The essential oils were analysed by GC and GC/MS and assayed for their total phenolics content, by the Folin-Ciocalteu method, and antioxidant effectiveness, using the 2,2-diphenyl-1-picrylhydrazil (DPPH) radical scavenging assay. The main components of these essential oils, from Nefza, Bargou and Krib, were p-cymene (36%, 40% and 46%), thymol (32%, 39% and 18%), gamma-terpinene (24%, 12% and 16%) and carvacrol (2%, 2% and 15%), respectively). The ability to scavenge the DPPH radicals, expressed by IC50, ranged from 59 to 80 mg L-1. The total phenolic content, expressed in gallic acid equivalent (GAE) g kg(-1) dry weight, varied from 9.37 to 17.70 g kg(-1) dw. CONCLUSIONS: A correlation was identified between the total phenolic content of the essential oils and DPPH radical scavenger capacity. The occurrence of a p-cymene chemotype of O. glandulosum in the northern region of Tunisia is demonstrated

Effect of water and salt stresses on germination of some acacia species in Tunisia

This work has focused on the study of germination characteristics of seeds of Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan, a species native of Tunisia, and of two introduced species : Acacia salicina Lindl. and Acacia ampliceps Maslin, reforested in arid zones of Tunisia. Germination was followed under conditions of water and salt stresses. Pre-treatments designed to remove integumentary inhibitions were applied to seeds. The germination behaviour of acacias in osmotic stress conditions showed a treatment effect, concentration of PEG 6000, highly significant on germination rate and mean time of germination. We found that these species did not tolerate drought and we observed a complete inhibition of germination at -0.8 MPa. The study of the effect of salt stress on germination showed a better tolerance of Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan to salinity than the other two species as it germinated at high salt concentrations. Indeed, at 18 g/l the germination rate reached 32 %. We didn’t find any relationship between seed germinative properties and ecology of the adult plantNotre travail a porté sur l'étude des caractéristiques germinatives des semences d'Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan, espèce autochtone de la Tunisie et deux espèces introduites Acacia salicina Lindl. et Acacia ampliceps Maslin qui sont utilisées en reboisement dans les zones arides de la Tunisie. La germination a été suivie en conditions de stress hydrique et salin. Des prétraitements destinés à lever les inhibitions tégumentaires ont été appliqués aux semences. Le comportement germinatif des acacias en conditions de stress osmotique a mis en évidence un effet traitement hautement significatif concernant le taux de germination et le temps moyen de germination. Nous avons révélé que ces espèces ne tolèrent pas la sécheresse et nous avons observé une inhibition totale de germination à -0.8 MPa. L'étude de la contrainte saline sur la germination a révélé une meilleure tolérance à la salinité de l'Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan par rapport au deux autres espèces puisqu'il a germé à des concentrations élevées de sel. En effet, à 18 g/l le taux de germination atteint 32 %. Enfin nos travaux n'ont pas mis en évidence de relation entre les propriétés germinatives des semences et l'écologie de la plante au stade adulte

Étude des secteurs écologiques, du milieu physique et des caractéristiques de production de la steppe arborée à Acacia tortilis dans le parc national de Bouhedma (Tunisie méridionale)

Ecology, physical and production characteristics of the steppe with Acacia tortilis in the Bouhedma national park (Tunisia southernmost). The present study was conducted in the Bouhedma national park and its surroundings, located in the arid area of Tunisia and considered a Biosphere reserve by UNESCO in 1977 ; it is a protected area with special ecological characteristics and an important dynamics of space occupation. The park contains the only wooded steppe with Acacia tortilis (Forsk.) Hayne subsp raddiana (Savi.) Brenan var. raddiana Brenan in Tunisia. With the aim of safeguarding and management of the park, a better knowledge of the distribution patterns and dynamics of the vegetation of this zone makes it possible to consider programmes of restoration and sustainable management of the natural environment. Based on the interpretation of remote sensing data and use of SIG, the study was devoted to the elaboration of charts relating to the ecological systems present in 2005, and to the distribution of the steppe with Acacia tortilis according to physical factors such as slope, altitude, type and depth of the soil. Also, the production of seeds was studied to explain the effect of physical factors on the regeneration of the species. The analysis of soil occupation dynamics translates into a good distribution (7056 ha) of steppe with Acacia tortilis. The study shows that Acacia tortilis is located on 6242 ha at an altitude of 20 m to 150 m and on 814 ha at an altitude from 150 to 250 m. This species grows on 5815 ha with a weak slope (0 to 3 %), on 928 ha with a slope of 3 to 5 % and only on 313 ha with a slope > 5 %. The results show that the Acacia tortilis is regenerated on the not very advanced soil of hydrous contribution with a surface of 3832 ha, on rendzina with 1280 ha, the isohumic soil with a surface of 986 ha. Acacia tortilis colonizes the far from deep soil with a surface of 2796 ha, the fairly deep soil with a surface of 2175, the very deep soil with a surface of 1970 ha, the not very deep soil with a surface of 75 ha and the deep soil with a surface of 40 ha.La présente étude a été effectuée dans le parc national de Bouhedma situé dans les zones arides tunisiennes et considéré comme une réserve de la biosphère de l’Unesco dès 1977. Le parc abrite l’unique steppe arborée à Acacia tortilis (Forsk.) Hayne subsp raddiana (Savi.) Brenan var. raddiana Brenan en Tunisie. L’étude a été consacrée, grâce à l’interprétation des données de la télédétection et l’utilisation des SIG, à l’élaboration des cartes relatives aux systèmes écologiques présents en 2005 et aux facteurs physiques du milieu (pente, altitude, type du sol, profondeur du sol). L’analyse du système écologique montre que la dynamique de l’occupation des sols se traduit par une bonne répartition de steppe arborée à Acacia tortilis avec une superficie de 7056 ha. L’étude montre qu’Acacia tortilis se localise sur 6242 ha à une altitude de 20 m à 150 m et sur 814 ha à une altitude de 150 à 250 m. Cette espèce pousse sur 5815 ha avec une faible pente (0 à 3 %), sur 928 ha avec une pente de 3 à 5 % mais seulement sur 313 ha avec une pente > 5 %. Les résultats montrent qu’Acacia tortilis se régénère fortement sur les sols peu évolués d’apport hydrique et sur les sols très peu profonds à profonds.Jaouadi Wahbi, Mechergui Kaouther, Gader Ghazi, Khouja Mohamed Larbi. Étude des secteurs écologiques, du milieu physique et des caractéristiques de production de la steppe arborée à Acacia tortilis dans le parc national de Bouhedma (Tunisie méridionale). In: Revue d'Écologie (La Terre et La Vie), tome 68, n°2, 2013. pp. 143-156

Effet des contraintes hydrique et saline sur la germination de trois espèces d’acacias en Tunisie

Effect of water and salt stresses on germination of some acacia species in Tunisia. This work has focused on the study of germination characteristics of seeds of Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan, a species native of Tunisia, and of two introduced species : Acacia salicina Lindl. and Acacia ampliceps Maslin, reforested in arid zones of Tunisia. Germination was followed under conditions of water and salt stresses. Pre-treatments designed to remove integumentary inhibitions were applied to seeds. The germination behaviour of acacias in osmotic stress conditions showed a treatment effect, concentration of PEG 6000, highly significant on germination rate and mean time of germination. We found that these species did not tolerate drought and we observed a complete inhibition of germination at -0.8 MPa. The study of the effect of salt stress on germination showed a better tolerance of Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan to salinity than the other two species as it germinated at high salt concentrations. Indeed, at 18 g/ l the germination rate reached 32 %. We didn’t find any relationship between seed germinative properties and ecology of the adult plant.Notre travail a porté sur l’étude des caractéristiques germinatives des semences d’Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan, espèce autochtone de la Tunisie et deux espèces introduites Acacia salicina Lindl. et Acacia ampliceps Maslin qui sont utilisées en reboisement dans les zones arides de la Tunisie. La germination a été suivie en conditions de stress hydrique et salin. Des prétraitements destinés à lever les inhibitions tégumentaires ont été appliqués aux semences. Le comportement germinatif des acacias en conditions de stress osmotique a mis en évidence un effet traitement hautement significatif concernant le taux de germination et le temps moyen de germination. Nous avons révélé que ces espèces ne tolèrent pas la sécheresse et nous avons observé une inhibition totale de germination à -0.8 MPa. L’étude de la contrainte saline sur la germination a révélé une meilleure tolérance à la salinité de l’Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan par rapport au deux autres espèces puisqu’il a germé à des concentrations élevées de sel. En effet, à 18 g/ l le taux de germination atteint 32 %. Enfin nos travaux n’ont pas mis en évidence de relation entre les propriétés germinatives des semences et l’écologie de la plante au stade adulte.Jaouadi Wahbi, Mechergui Kaouther, Hamrouni Lamia, Hanana Mohsen, Khouja Mohamed Larbi. Effet des contraintes hydrique et saline sur la germination de trois espèces d’acacias en Tunisie. In: Revue d'Écologie (La Terre et La Vie), tome 68, n°2, 2013. pp. 133-141

Les activités biologiques et les propriétés de l'huile de L'Origanum glandulosum Desf

Origanum glandulosum Desf. (Species endemic of North Africa: Tunisia and Algeria) is important medicinally as it has antimicrobial, antifungal, antioxidant, antibacterial, antithrombin, antimutagenic, angiogenic, antiparasetic and antihyperglycaemic activities. Phytochemical investigations of the species of this genus have resulted in the extraction of a number of important bioactive compounds. This emphasizes on the need of extensive study for reporting the additional information on the medicinal importance, the biological activities and properties of oil of other unattended species of Origanum glandulosum. © 2015 Springer-Verlag France

Morphological characteristics and variation of wood, cone and seed productions in the reforestation of Aleppo pine in Northeastern Tunisia using terrestrial and spatial index approaches

For several decades, forest management policies have encouraged land cover changes, with the establishment of tree cover such as Aleppo pine in natural or degraded ecosystems for soil protection and the firewood production. In order to investigate the importance of Aleppo pine trees in the ecosystem, this study was conducted in the reforestation of the Aleppo pine of Northeastern Tunisia. The production of wood, cones and seeds of Aleppo pine in the 6 date reforestation in Northeastern Tunisia were surveyed using 6 plots (20 tree/plot) spread over 6 different location. Our hypothesis was to determine the characteristics that can be decisive in estimating the production of Aleppo pine in reforestation in Tunisia using terrestrial and spatial measurements including (i) age, (ii) dendrometric characteristics, (iii) silvicultural treatments, (iv) stationary data and/ or (v) remote sensing parameter (NDVI: Normalized Difference Vegetation Index). We found that the Aleppo pine in Northeastern Tunisia and at young age trees (14–35 years) were more productive than the regeneration or reforestation stand, either young or old, in Northwest of Tunisia. Wood, cone and seed productions were significantly different amongst the plots (p <0.05). The NDVI was positively correlated with the production of wood, cones and seeds. Stand age, exposure and longitude were also positively correlated with the production. However, longitude and altitude were negatively correlated with the production, showing a negative effect on the morphological traits of trees and, subsequently, their growth. The regression analysis indicates that NDVI and age were the most determinant factors of seed production. This research suggests that reforestation planning, particularly the choice of altitude and latitude, may result in improved tree morphology that may increase Aleppo pine wood seed and cone crops

Chemical composition and antioxidante activity of Tunisian Origanum glandulosum Desf. essential oil and volatile oil obtain by supercritical CO2 extraction

Dried flowers and leaves of Origanum glandulosum Desf. were submitted to hydrodistillation (HD) and supercritical fluid extraction with CO2 (SFE). The essential oils isolated by HD and volatile oils obtained by SFE were analysed by GC and GC/MS. Total phenolics content and antioxidant effectiveness were performed. The main components of the essential oils from Bargou and Nefza were: p-cymene (40.4% and 39%), thymol (38.7% and 34.4%) and γ- terpinene (12.3% and 19.2%), respectively. The major components obtain by SFE in the volatile oil, from Bargou and Nefza, were: p-cymene (32.3% and 36.2%), thymol (41% and 40%) and γ-terpinene (20.3% and 13.3%). Total phenolic content, expressed in gallic acid equivalent (GAE) g kg-1 dry weight, varied from 12 to 27 g kg-1 dw, and the ability to scavenge the DPPH radicals, expressed by IC50 ranged from 44 to143 mg L-1