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Non-woody biomass species have high-energy potentials, which could be used for bioenergy production. Invasive species are species spreading into areas, where they are not native, consequently causing environmental and economic problems. Therefore, the present study evaluated the proximate, ultimate, chemical, and fuel characteristics of wood and charcoal of three invasive non-forest tree species in Saudi Arabia: Calotropis procera, Rhazya stricta, and Phragmites australis, which were compared with the wood of Acacia tortilis, a preferable local fuelwood. All these data were discussed to investigate the possibility of using the invasive plants for energy production. The thermal behavior of wood was analyzed using thermo-gravimetric and derivative thermo-gravimetric methods. Overall, compared with the wood of A. tortilis, the woods of R. stricta and P. australis are suitable for energy production. The charcoal produced from P. australis emitted less nitrogen (N) oxide than that of R. stricta.

The present study was carried out in central region of Saudi Arabia. The objective of the study was to evaluate the diversity, stocking and regeneration capacity of the natural growing Acacia gerrardii (Benth) in 5 sites selected from three governments namely; Huraymila’, Dhurmah and Dawadmi. The sampling of Acacia species was conducted within circular sample plots. Inside each site, three sample plots were selected to determine the regeneration capacity, tree stocking and productivity. The results indicated that the growth diversity and stand structure of naturally growing Acacia gerrardii in Riyadh region varied with location. Most of the trees in locations occurred as woodlots. Dawadmi recorded the maximum tree stocking and productivity. The regeneration capacity in Huraymila’ was higher whereas the least total seedling ha-1 was record at Dawadmi location. Removing trees for various purposes reduced heavily the stocking density of the trees, regeneration capacity and the chlorophyll contents in locations. The stocking density and regeneration in locations were low cause of indiscriminate cutting of trees and intensive grazing. Tree heights were below the average as a result to low stocking density and increased natural spacing between trees. Acacia gerrardii woodlots in this area require immediate intervention and protection to attain sustainability.

The objective of this study was to characterize the properties of pulp and paper manufactured from two agricultural residues namely, wheat straw (Triticum aestivum L. em Thell.) and date palm midribs (Phoenix dactylifera L.) widely available in Saudi Arabia by employing soda-anthraquinone (AQ) pulping process. Specimens from cedar wood (Juniperus procera Hochst. ex Endl.) wood was also used as control samples. Chemical and the morphological characteristics of all three types of raw materials in addition to basic properties of hand sheets made from such resources were evaluated. The results indicated that wheat straw had the highest hemicellulose and ash values of 35% and 7% and the lowest lignin content value of 18%, respectively. The fibre length of the both palm fronds and wheat straw was lower than that of 2.2 mm which was found for J. procera. Overall strength properties of the handsheet made from two agricultural raw materials were significantly lower than those made from J. procera pulp. Wheat straw handsheets also had higher strength properties than those made from date palm midribs with an exception of their tear index. Based on the results of this study it appears that both types of raw materials, date palm midribs and wheat straw could have a potential to manufacture pulp and paper with accepted properties so that such underutilized species can be converted into value-added products.

Leucaena leucocephala trees are commonly known as White Lead tree. It is native to Southern Mexico and Northern Central America and spread across many tropical and sub-tropical locations. It has multipurpose uses, such as generation of firewood, timber, greens, fodder, and green manure, as well as to provide shade and control soil erosion. It has been used for medicinal purposes because of possessing multiple pharmacological properties. Studies have shown the presence of various secondary metabolites such as alkaloid, cardiac glycosides, tannins, flavonoids, saponins, and glycosides in this species. In traditional medicine, it is used to control stomach ache and as contraception and abortifacient. In the present study, the global distribution, taxonomy, chemical composition, pharmacological activities, and potential uses of Leucaena leucocephalaare discussed.