The mutually antagonistic effect of drought and sand burial enables the biocrust moss <i>Bryum argenteum</i> Hedw. to survive the two co-occurring stressors in an arid sandy desert

Abstract

Abstract. Biocrust moss is an essential soil surface bio-cover. It represents the highest succession stage among the diverse range of surface-dwelling cryptogams (e.g., cyanobacteria, green algae, and lichen, which are also referred to as biological soil crusts) and makes a major contribution to soil stability and fertility throughout arid 10 desert ecosystems. The soil surface represents a small ecological niche that is poikilohydric in nature. Biocrust moss is therefore highly susceptible to drought and sand burial, which are two ubiquitous stressors in arid sandy deserts. However, little information is available regarding the mechanism by which biocrust moss can survive and flourish in these habitats when stressed simultaneously by the two stressors. The combined effects of drought and sand burial were evaluated in a field experiment using the predominant biocrust moss, Bryum 15 argenteum Hedw., in the Tengger Desert, China. Drought was simulated by applying distilled water in three artificial rainfall regimes at 8-day intervals in spring and autumn: 4 and 6 mm (average rainfall, control), 2 and 3 mm (double drought), and 1 and 1.5 mm (fourfold drought), respectively. The effect of sand burial was determined by applying six treatments, i.e., sand depths of 0 (control), 0.5, 1, 2, 4, and 10 mm. The four parameters of chlorophyll a content, PSII photochemical efficiency, regeneration potential, and shoot upgrowth 20 were evaluated in the moss. It was found that the combined effects of drought and sand burial did not exacerbate the single negative effects of the four parameters tested. Drought significantly ameliorated the negative effects of deep sand burial on the retention of chlorophyll a content, PSII photochemical efficiency, and regeneration potential of B. argenteum. Sand burial diminished and even reversed the negative effects of Biogeosciences Discuss., https://doi