Allelopathic Effects of Introduced Eucalyptus Gomphocephala Extracts on Germination and Seedling Growth of Native Ceratonia siliqua in Libya

The present study aimed to investigate the allelopathic effects of leaf aqueous extracts of introduced Eucalyptus gomphocephala L. (donor species) were collected during different growing seasons at different concentrations (0, 25, 50, 75, and 100% v/v) on germination percentage, average germination time, plumule and radical length, dry weight of radical and plumule and seedling vigor index (SVI) of native Ceratonia siliqua L. (recipient species) seedlings under laboratory conditions. Results suggested that the germination percentage and all growth parameters of C. siliqua were significantly reduced gradually with the increase of aqueous extract concentration levels and the reduction was varied and could be extract concentration and growing season dependent. The highest phytotoxic effect on germination and seedling growth was exhibited by E. gomphocephala aqueous extract at 100% concentration, followed by 50% concentration. Generally, it is concluded that the allelopathic effect of introduced E. gomphoracephala trees on native Ceratonia siliqua trees has been weak or no effectiveness in some cases under laboratory conditions. Keywords: Eucalyptus gomphocephala; Introduced species; Libya; Allelopathy; Ceratonia siliqua

Natural durability of four Tunisian Eucalyptus spp. and their respective compositions in extractives

Eucalyptus trees have been adapted to the Tunisian climate. Now, they need to be economically valued. Tunisian Eucalyptus have great technological properties allowing us to use them as wooden material. However, there is large variability in the natural durability between heartwood Eucalyptus spp. The wood sustainability assessment provides reliable parameters to predict the service life of wood-based products. This study aimed to evaluate the wood deterioration of four North Tunisian fast-growing Eucalyptus spp. (Eucalyptus maidenii, Eucalyptus saligna, Eucalyptus camaldulensis and Eucalyptus gomphocephala) exposed to basidiomycetes (Coniophora puteana and Trametes versicolor) and termite (Reticulitermes flavipes) attacks. Among the four Eucalyptus woods, Eucalyptus gomphocephala presents the highest decay and termite resistance. The four Eucalyptus wood species are classified as very durable against fungal degradation and durable against termite attacks, expect for Eucalyptus saligna which is classified as sensible against termites. The natural durability of Eucalyptus seems to be mainly caused by extractives, and a lot of compounds are involved. Antifungal and anti-termite properties of these compounds were put in perspective with the natural durability of wood. Gas chromatography-mass spectrometry (GC-MS) analyses highlighted that Eucalyptus durability is mostly governed by gallic acid, fatty acid glycerides, fatty acid esters, phenolic compounds, sitosterol, catechin and ellagic acid.

Relationship between the common brushtail possum (Trichosurus vulpecula) and tuart (Eucalyptus gomphocephala) tree decline in Western Australia

Forest canopy loss due to plant pathogens, insect or abiotic factors significantly alters habitat and resource availability for animals, which has flow-on effects for whole ecosystems. The tuart (Eucalyptus gomphocephala) has been in decline throughout its geographic range; this is likely associated with watertable and salinity changes, although a plant pathogen (Phytophthora multivora) has also been implicated. We examined the relative abundance of common brushtail possums (Trichosurus vulpecula) across 12 sites (each 0.72 ha) selected on the basis of the health of dominant tuart trees (six ‘healthy’ and six ‘declining’ sites). Habitat variables (understorey, tuart dimensions and density, tree hollows, tree-to-trap distance) and tuart tree health (crown loss, epicormic regrowth) were compared with possum abundance. Possums were detected at most sites. There was no significant difference between brushtail possum numbers at ‘healthy’ or ‘declining’ sites, although marginally more possums were recorded at declining sites (5.7 ± 1.5 (s.e.), n = 6 sites) compared with healthy sites (3.3 ± 0.7; Cohen’s effect size d = 0.80). Slightly higher abundance of possums was associated with sites that had a greater density of smaller-diameter but taller tuart trees. ‘Declining’ sites, with more epicormic regrowth and greater tree densities, may provide more palatable food resources for possums.

Influence of intermittent and continuous microwave heating on drying kinetics and wood behavior of Eucalyptus Gomphocephala

The aim of this work was to determine the microwave drying kinetics of Eucalyptus Gomphocephala wood and to investigate the influence of intermittent and continuous heating processes on the end quality of dreid samples. The average moisture content evolution and temperature of wood samples under different microwave powers were analyzed in terms of drying time and internal temperature level. Results show that the increase of microwave power level decreses the drying time and increases the internal wood temperature. Based on qualitative observations on the state of dried samples, the intermittent microwave powers intensity process present the optimal processing parameter in microwave drying of Eucalyptus wood species.Keywords: microwave drying; power; intermittent; continuous; Eucalyptus wood.

New xenophytes from the Canary Islands (Gran Canaria and Tenerife; Spain)

Recent fieldwork in Gran Canaria and Tenerife (Canary Islands, Spain), mostly between 2012 and 2016, yielded new chorological data for several non-native vascular plant species. The following are considered naturalized and/or potentially invasive: Callistemon viminalis, Casuarina glauca, Chloris barbata, Cyperus difformis, Eucalyptus gomphocephala, E. sideroxylon, Nephrolepis cordifolia, Rumex palustris, Senna × artemisioides (s.l.) and S. × floribunda and are reported for the first time from the Canary Islands. Other first records include: Cascabela thevetia (Tenerife), Cyclospermum leptophyllum (Gran Canaria), Digitaria radicosa (Gran Canaria, Tenerife), Dysphania anthelmintica (Tenerife), Erythrostemon gilliesii (Tenerife), Heliotropium supinum (Tenerife), Limoniastrum monopetalum (Tenerife), Nerium oleander (Tenerife), Pascalia glauca (Tenerife), Phytolacca americana (Tenerife), Podranea ricasoliana (Gran Canaria), Psidium guajava (Gran Canaria), Rumex cristatus (Tenerife), Schinus terebinthifolia (Tenerife), Solandra maxima (Tenerife), Tipuana tipu (Tenerife) and Youngia japonica (Gran Canaria). More than 20 additional taxa also represent chorological novelties but are considered ephemerals. Finally, miscellaneous notes are added for Diplachne fusca subsp. uninervia, Eclipta prostrata, Pluchea carolinensis, Prosopis juliflora and Sida rhombifolia from Gran Canaria.