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Long-term protection of arid ecosystems changes the vegetation and soil structures. The quantification of aboveground biomass and carbon content are among the principal indicators to evaluate these changes. Most methods used to quantify these parameters are costly, time consuming and destructive. In this paper, two non-destructive methods were compared: digital image processing and biometric measurements. Aboveground biomass and carbon content of five perennial shrubs were studied inside and outside Sidi Toui National Park, southern Tunisia. The effect of long-term protection on aboveground biomass and carbon content was assessed. The main results indicated that both methods provided similar aboveground biomass and carbon values. Aboveground biomass and carbon content were strongly correlated with canopy cover and biovolume (R2 ˃ 0.7). Positive linear relationships were found for all the studied species. Apart from the large canopy cover of Haloxylon schmittianum and Haloxylon scoparium, the obtained results showed that long-term protection had no significant effect on aboveground biomass and carbon content for the other species. These results suggest that digital charting technique is an accurate method for assessing rangeland productivity in a timely and cost-efficient manner and that long-term protection is not always suitable for enhancing carbon content and therefore ecosystem resilience under climate change conditions. [ABSTRACT FROM AUTHOR]

Artemisia herba-alba is an important component of Mediterranean dry steppe floras, being widely distributed in arid areas of the Iberian Peninsula and North-West Africa. In this study, we use genetic, cytogenetic and niche modelling tools to investigate the natural history of the species, focusing particularly on the role played by polyploidization to explain current diversity patterns throughout the main distribution range of the plant. Our sequencing data indicate a complex phylogeographical structure showing similar haplotype diversity patterns on both sides of the Strait of Gibraltar and no clear signals of genetic refugia. According to our cytogeographical results, we inferred multiple polyploidization events, which probably took place on the Iberian Peninsula and in North Africa independently. Environmental niche modelling suggested stable potential distributions of A. herba-alba on both sides of the Mediterranean Sea under present and past Last Glacial Maximum conditions, which could be related to the intricate spatial genetic and cytogenetic patterns shown by the species. Finally, environmental modelling comparison among cytotypes revealed that the niche of tetraploids is narrower and nested in that of diploids, a result that could indicate environmental specialization and could potentially explain recurrent establishment success of tetraploids. [ABSTRACT FROM AUTHOR]

Atriplex mollis Desf. (Amaranthaceae), a North African endemic halophytic species, is further described in this study. Phylogenetic analysis based on a combined dataset of ITS and ETS rDNA and atpB-rbcL and trnK cpDNA showed that A. mollis is closely related to the Malta- and Gozo-endemic Cremnophyton lanfrancoi Brullo & Pavone. Given this close phylogenetic relationship, A. mollis is also considered among the oldest species of Atriplex, together with C. lanfrancoi. Molecular data also suggest that A. mollis in North Africa, C. lanfrancoi on Malta Island, and Atriplex cana Ledeb. in Eurasian semideserts constitute a separate clade within the tribe Atripliceae. As an 18-month-old shrub, A. mollis can reach a mean height of 44.06 ± 8.09 cm with a leaf area around 1.24 ± 0.15 cm², and can produce seeds in order of 113.08 ± 28.52 g plant−1. The anatomy of A. mollis shows the presence of male and female developed flowers. Hermaphroditic flowers that may lead to the appearance of male flowers with underdeveloped female organs were rarely found. Three main shapes of ovule (campylotropous, amphitropous, and orthotropous) were found in A. mollis. [ABSTRACT FROM AUTHOR]