Agro-wastes, such as crop residues, leaf litter, and sawdust, are major contributors to global greenhouse gas emissions, and consequently a major concern for climate change. Nowadays, mushroom cultivation has appeared as an emerging agribusiness that helps in the sustainable management of agro-wastes. However, partial utilization of agro-wastes by mushrooms results in the generation of a significant quantity of spent mushroom substrates (SMS) that have continued to become an environmental problem. In particular, Shiitake (Lentinula edodes Berk.) mushrooms can be grown on different types of agro-wastes and also generate a considerable amount of SMS. Therefore, this study investigates the biotransformation of SMS obtained after Shiitake mushroom cultivation into biogas and attendant utilization of slurry digestate (SD) in tomato (Solanum lycopersicum L.) crop fertilization. Biogas production experiments were conducted anaerobically using four treatments of SMS, i.e., 0% (control), 25, 50, and 75% inoculated with a proportional amount of cow dung (CD) as inoculum. The results on biogas production revealed that SMS 50% treatment yielded the highest biogas volume (8834 mL or 11.93 mL/g of organic carbon) and methane contents (61%) along with maximum reduction of physicochemical and proximate parameters of slurry. Furthermore, the biogas digestate from 50% treatment further helped to increase the seed germination (93.25%), seedling length (9.2 cm), seedling root length (4.19 cm), plant height (53.10 cm), chlorophyll content (3.38 mg/g), total yield (1.86 kg/plant), flavonoids (5.06 mg/g), phenolics (2.78 mg/g), and tannin (3.40 mg/g) contents of tomato significantly (p < 0.05) in the 10% loading rate. The findings of this study suggest sustainable upcycling of SMS inspired by a circular economy approach through synergistic production of bioenergy and secondary fruit crops, which could potentially contribute to minimize the carbon footprints of the mushroom production sector.

The role of heritage sites as a shelter for biodiversity is overlooked. Eight archeological sites representing different landscapes in Alexandria City were surveyed, from which 59 stands were sampled between April 2019 and March 2021. The archeological sites and the relictual landscapes are geographically dispersed and are arranged here from west to east, representing the full range of environmental variation within the study area. The selection of stands in each site was based on the area and the variability within the habitats, the physiography, and the levels of disturbance. A composite soil sample was collected from each site. Two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis (DECORANA) were carried out to identify the plant communities in the study area. The recorded taxa, their national geographical distribution, life forms, habitats, chorological types, and vegetation groups are listed. A total of 221 specific taxa, 172 native and 49 alien non-native species (representing some 10.3% of the whole range of Egyptian flora), belonging to 150 genera and 44 families, are reported in the present study. Only two endemic species were recorded in the studied urban habitats. The phytosociological analysis of the sites showed differences among vegetation types found in the archeological sites as a function of the varying degrees of enthronization. A significant effect of archeological site and relictual landscape on species diversity was observed as indicated using the richness, Shannon’s and Simpson’s indices. Flat plains are substantially more diverse than any of the other habitats in the present study, followed by the habitat of rocky ridge slope. The present study found evidence of an ecological legacy that persists today within the semi-arid climatic ecosystem of Alexandria City. The study highlights the urgent need for measures to maintain cultural landscapes while considering the conservation of biodiversity within the archeological sites. It is hoped that the outcomes of the current study can provide guidance on the potential integration of biodiversity conservation in planning the management of archeological sites.

Healthy coastal sabkhas (sabkha is an Arabic term for a salt flat) offer plenty of ecosystem services including climate change mitigation. However, fewer research studies were conducted at coastal sabkhas compared to other coastal marshes. This study was conducted in a total of ten coastal sabkha sites with different vegetation covers along the southern Red Sea coast of Saudi Arabia. The main objectives were to model and predict the distribution of volumetric soil organic carbon (SOC) density (kg C/m³) and cumulative SOC stocks (kg C/m²) using three different mathematic functions (allometric, exponential, and sigmoid) based on sampled and observed soil carbon (C) data (total of 125 soil cores = 1250 soil samples). Sigmoid function showed the greatest fit for predicting the distribution of volumetric SOC density over soil profile depth with mean Adj. R² = 0.9978, 0.9611, and 0.9623 for vegetation cover of >25–50, >50–75, and >75–100%, respectively. For modeling the cumulative SOC stocks, both validation indices and p of the t-test confirmed that using the exponential function is the most appropriate to be used for predicting the SOC stock among different vegetation covers. Moreover, assessing the topsoil concentration factors (TCFs) showed that the distribution of the SOC content is impacted to a great extent by the vegetation cover at coastal sabkhas. Sampling the soil parameter of interest to estimate the SOC stocks is constrained by time and cost. Therefore, using the exponential function for predicting the distribution of cumulative SOC stocks at coastal sabkhas over soil profile depth is appropriate and promising for mapping SOC stocks at both regional and global spatial scales.

In this study, we explored the capacity for two promising macrophytes, Typha domingensis and Typha elephantina, to be used for the surveillance of contamination by six metals, i.e., Cu, Fe, Mn, Ni, Pb, and Zn, in the mountainous area of Taif City in Saudi Arabia. Regression models were generated in order to forecast the metal concentrations within the plants’ organs, i.e., the leaves, flowers, peduncles, rhizomes, and roots. The sediment mean values for pH and the six metals varied amongst the sampling locations for the respective macrophytes, indicating that similar life forms fail to indicate equivalent concentrations. For instance, dissimilar concentrations of the metals under investigation were observed within the organs of the two rooted macrophytes. The research demonstrated that the segregation of metals is a regular event in all the investigated species in which the metal concentrations vary amongst the different plant constituent types. In the current study, T. domingensis and T. elephantina varied in their capacity to absorb specific metals; the bioaccumulation of metals was greater within T. domingensis. The relationships between the observed and model-estimated metal levels, in combination with high R² and modest mean averaged errors, offered an appraisal of the goodness of fit of most of the generated models. The t-tests revealed no variations between the observed and model-estimated concentrations of the six metals under investigation within the organs of the two macrophytes, which emphasised the precision of the models. These models offer the ability to perform hazard appraisals within ecosystems and to determine the reference criteria for sediment metal concentration. Lastly, T. domingensis and T. elephantina exhibit the potential for bioaccumulation for the alleviation of contamination from metals.

Jabal Al-Ward is one of the Hijazi mountains situated between Al-Ulā and Al-Wajh, southwest Tabuk Province, Saudi Arabia’s northwesterly border region. It is considered the highest mountain in this area and is enriched in wildlife. For the first time, the present research aimed to investigate the floristic composition, phytogeographical distribution, and plant diversity in Jabal Al-Ward. One hundred ninety-eight species representing 47 plant families have been identified. The Asteraceae, Poaceae, and Fabaceae represented more than a third of the region’s floristic composition. The perennial species (53.5%) were dominant over the annuals (46.46%). This is a prominent feature in Jabal Al-Ward, where the perennial species may be more tolerant of climatic changeability than the annuals. Seven life form categories were found; therophytes (46.46%) showed to be the most common life form. In addition, there were four main phytogeographical groups: Mono-regional, Bi-regional, Pluri-regional, and Worldwide. The Mono-regional and Bi-regional categories had the highest participation, with 38.5% and 37.4%, respectively. Thirty-six species (18.2%) were found to be native to the Saharo-Arabian region. The Saharo-Arabian region was combined with eight more regions, including Saharo-Arabian/Sudano-Zambesian (12.6%), Irano-Turanian/Saharo-Arabian (9.1%), Mediterranean/Saharo-Arabian (5.6%), Irano-Turanian/Mediterranean/Saharo-Arabian (4.5%), Irano-Turanian/Saharo-Arabian/Sudano-Zambesian (2%), Euro-Siberian/Irano-Turanian/Mediterranean/Saharo-Arabian and Saharo-Arabian/Sudanian (1% each), Mediterranean/Saharo-Arabian/Sudano-Zambesian, and Irano-Turanian/Mediterranean/Saharo-Arabian/Saharo-Zambesian (0.5% each). The current study demonstrated the highest species richness compared to earlier research on various locations in Tabuk Province. In future work, the species and endemic richness along elevation gradients should be studied in Jabal Al-Ward. As well as the IUCN status of each taxon, the DNA barcoding of endangered species will be of great significance if applied in the surveyed area.