Abundance and Distribution of the Forest Cockroaches in Different Algerian Ecosystems

Forests have many insect species that are unique to biodiversity and play a crucial role in the functioning of ecosystems. Forest cockroaches are the best example of forest litter insects, which also help decompose fallen leaves. The composition of the Blattoptera fauna can vary from one region to another, depending on the habitat and numerous biotic and abiotic factors In order to study the diversity, abundance, and distribution of forest cockroaches in different Algeria ecosystems, we have selected four sites from three Wilayas: Senalba (Djelfa), Ain achir (Annaba), Seraidi (Annaba), and Lehnaya (El-taref). These sites are classified into two distinct forest groups (Pinus halepensis and Quercus canariensis). In all areas, the samples were collected each month manually, starting from April 2019 until March 2020. We have collected 1231 individuals of cockroaches and describe eight species from all locations: Loboptera ovolobata (Bohn, 1991), Loboptera decipiens (Germar, 1817), Ectobius kervillei (Bolivar, 1907), Dziriblatta nigriventris (Chopard, 1936), Dziriblatta stenoptera (Chopard, 1937), Phyllodromica zebra (Rhen, 1903), Dziriblatta sp. (Chopard, 1936) and some Ectobius (Stephens, 1835) specimens have not yet been identified. With 51% L. decipiens was the most abundant species, followed by L. ovolobata with 27%. Despite that, the number of larvae was substantially higher than the number of adults in all forests examined. However, the abundance and biodiversity of cockroaches in the Djelfa forest were greater than those of the other woods. This study made it possible to characterize the diversity and dynamics of cockroach species populations in different Algerian ecosystems according to diverse Mediterranean forests.

STRUCTURAL AND FLORISTIC CHARACTERIZATION OF THE OULED BECHIH FOREST (ALGERIA)

The objective of this study is the rational management of forest ecosystems for sustainable conservation of floristic biodiversity. Two types of analysis are carried out: structural analysis and analysis of the main species. A total of 22 families were identified, divided among 32 species. The dominant woody species are Quercus suber and Quercus canariensis. Fagaceae is the most represented family. The average values of species richness and Shannon diversity index are 4 ± 1.8 and 0.9 ± 0.30 species/plot respectively. The average density of woody species in the Oueld Bechih forest was 158 ± 28 tree/ha with an average basal area of 32.67 ± 0.74m²/ha. The height structure shows that trees in height classes is ≥ 6 has very high density, evidence of almost no natural regeneration. The total structure indicates that larger trees are more abundant. In effect, this work provides a database for the forest, but it represents only one facet to be considered in protecting and restoring it.

CHARACTERISATION AND ASSESSMENT OF THE DECLINE OF THE OULED BECHIH FOREST (ALGERIA)

The establishment of the state of the massif by a diagnosis on different forest plots is part of a project of monitoring and silvicultural management. The purpose of this study is to assess the health status of the Ouled Bechih forest. The methodology used was the visual assessment of the tree crown of the dominant species (i.e. Quercus suber and Quercus canariensis) according to the protocols DEPEFEU, DEPERIS and ICP Forests. These protocols were selected for adoption based on field observations and their applicability in record time. The results obtained indicate that the health status of the trees within the studied plots is declining. The DEPEFEU value index shows an average of 1.75 for Quercus suber and 2.6 for Quercus canariensis while the DEPERIS has an average level of 2.36 Q. suber in and 3.37 in Q. canariensis. ICP Forests has also contributed to providing clearer information on the consequences of this health situation by deducting an average visibility rate of 1.20 and 2.63; social status of 1.17 and 3.11 and competition of 1.11 and 2.49 for Q. suber and Q. canariensis respectively. In general, the health status of the tree crown is average and almost adapted to the environmental conditions. In contrast, the carrying capacity of biodiversity is low and needs to be improved.

Analyse morphologique et taxonomique du complexe Quercus faginea (Fagaceae) en Algérie (Morphological and taxonomic analysis of Quercus faginea (Fagaceae) complex in Algeria)

La systématique de Quercus faginea Lam. (s.l) (Fagaceae) reste encore indéfinie, d’autant plus qu’elle s’hybride avec d’autres espèces et qu’elle est polymorphe. Quatre sous-espèces ont été identifiées et présentement reconnues en péninsule ibérique et au Maroc, or, les données disponibles ne permettent pas de trancher entre les taxons présents en Algérie. Pour remédier au manque de données nécessaires, une analyse morphologique et taxonomique de treize populations du complexe dans le pays a été effectuée. Dans chacune, vingt feuilles et vingt bourgeons sur dix arbres matures ont été prélevés pour une description détaillée de 23 traits morphologiques. L’ACM (analyse des correspondances multiples) et la CAH (classification ascendante hiérarchique) ont été utilisées pour analyser les données et identifier des groupes homogènes. Une variabilité significative intra et inter-populationnelle est remarquable, avec une taille des feuilles qui tend à se diminuer en allant de l’est vers l’ouest et du nord au sud du pays. Cette variabilité ne permet pas, à elle seule, de différentier entre les populations étudiées, en revanche, les traits liés à la forme du limbe et aux types du tomentum sur la feuille s’avèrent plus utiles. Cette étude confirme que le complexe Q. faginea Lam. est représenté en Algérie par deux espèces : Quercus canariensis Willd. et Q. faginea Lam., lui-même représenté par deux taxons, subsp. faginea et subsp. broteroi. The systematics of Quercus faginea Lam. (s.l) (Fagaceae) remains obscure, as it tends to crossbreed with other species and show signs of polymorphism. Four subspecies were identified and currently recognized in the Iberian Peninsula and Morocco. However, the literature to date does not allow the distinction between the taxa present in Algeria. To remedy the lack of required data, morphological and taxonomic analysis of thirteen tree populations has been carried out in the country. In the process, twenty leaves and twenty buds from ten mature trees were collected at each population to produce a more detailed description of 23 particular morphological traits. MCA (multiple correspondence analysis) and AHC (agglomerative hierarchical clustering) were used to analyze the data and to identify homogeneous groups. The results obtained show high intra and inter-population variability, with leaf size diminishing from east to west and from north to south. Though the findings were remarkable, they alone could not be used to differentiate between populations under examination; the traits relating to limb shape and indumentum type on the leaf prove to be more useful. It is clear from this study that the Q. faginea Lam. group in Algeria is represented by two species: Quercus canariensis Willd. and Q. faginea Lam., the latter being represented by two taxa: subsp. faginea and subsp. broteroi

Shifts in Growth Responses to Climate and Exceeded Drought-Vulnerability Thresholds Characterize Dieback in Two Mediterranean Deciduous Oaks

Drought stress has induced dieback episodes affecting many forest types and tree species worldwide. However, there is scarce information regarding drought-triggered growth decline and canopy dieback in Mediterranean deciduous oaks. These species face summer drought but have to form new foliage every spring which can make them vulnerable to hotter and drier conditions during that season. Here, we investigated two stands dominated by Quercus frainetto Ten. and Quercus canariensis Willd. and situated in southern Italy and Spain, respectively, showing drought-induced dieback since the 2000s. We analyzed how radial growth and its responses to climate differed between non-declining (ND) and declining (D) trees, showing different crown defoliation and coexisting in each stand by: (i) characterizing growth variability and its responsiveness to climate and drought through time, and (ii) simulating growth responses to soil moisture and temperature thresholds using the Vaganov–Shashkin VS-lite model. Our results show how growth responsiveness to climate and drought was higher in D trees for both oak species. Growth has become increasingly limited by warmer-drier climate and decreasing soil moisture availability since the 1990s. These conditions preceded growth drops in D trees indicating they were more vulnerable to warming and aridification trends. Extremely warm and dry conditions during the early growing season trigger dieback. Changes in the seasonal timing of water limitations caused contrasting effects on long-term growth trends of D trees after the 1980s in Q. frainetto and during the 1990s in Q. canariensis. Using growth models allows identifying early-warning signals of vulnerability, which can be compared with shifts in the growth responses to warmer and drier conditions. Our approach facilitates establishing drought-vulnerability thresholds by combining growth models with field records of dieback.

Physical properties of four ring-porous hardwood species: influence of wood rays on tangential and radial wood shrinkage

Some relationships between ray proportions, strength and shrinkage properties and basic density in hardwood species were highlighted. A better understanding of their relationships caused by the variation in moisture content in the hygroscopic domain could be a key factor in determining of wood stability properties and to determine the choice of a specific wood species according to its service life condition. The objectives of this study were (i) to determine the physical properties of various ring porous wood species (ii) and to evaluate the influence of wood rays (according to their proportions and volume) on physical properties of wood and more particularly on the Transverse Anisotropy Ratio for Shrinkage (TARS). This study focused on four ring-porous hardwood species; Castanea sativa, Quercus canariensis, Quercus petraea and Quercus robur, differing by the presence and abundance of their multiseriate wood rays. Basic densities, tangential shrinkages, radial shrinkages and the TARS of heartwood and sapwood from each wood species were determined. Wood-rays’ proportions and volume were measured by the image analysis method, and their influence on the last three shrinkages was investigated. A significant correlation between wood ray proportions, wood shrinkage values and basic density was observed.