Antagonistic effects of drought and sand burial enable the survival of the biocrust moss <i>Bryum argenteum</i> in an arid sandy desert

Abstract

Abstract. Biocrust moss is an essential soil surface bio-cover. It can represent the latest succession stage among the diverse range of surface-dwelling cryptogams (e.g., cyanobacteria, green algae, and lichen, which are also referred to as biocrusts), and it can make a major contribution to soil stability and fertility in many arid sandy desert ecosystems. The soil surface represents a very large 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 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 (4-fold 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 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 the regeneration potential of B. argenteum. Sand burial diminished and even reversed the negative effects of drought on the maintenance of chlorophyll a content, PSII photochemical efficiency, and regeneration potential. Although drought and sand burial imposed an additive negative effect on shoot upgrowth, which suggested a trade-off between growth ability and stress tolerance, their mutually antagonistic effect on the physiological vigor of B. argenteum provided an opportunity for the biocrust moss to overcome the two co-occurring stressors. In addition to providing a strong stress tolerance, drought and sand burial may provide an important mechanism for the biodiversity maintenance of biocrust mosses in arid sandy ecosystems.

Amendments fail to hasten biocrust recovery or soil stability at a disturbed dryland sandy site

“…Soil destabilization caused by disturbance can bury biocrusts and thus potentially kill the dominant photosynthetic components, although limited burial has been known to protect mosses from drought conditions (Jia et al ). Disturbance can also detach microorganisms from the soil, leaving them vulnerable to off‐site movement by wind and water.…”

Effect of sand burial on the subcritical water repellency of a dominant moss crust in a revegetated area of the Tengger Desert, Northern China

“…Therefore, our initial hypothesis was that sand burial would significantly reduce moss crusts WR. The effects of sand burial on moss crusts are both depth-and moisture-dependent according to our previous study (Jia et al, 2018). Therefore, to test the hypothesis, the WRs of a typical moss crust dominated by Bryum argenteum Hedw., a pioneer species in the Shapotou revegetated area of the Tengger Desert, was measured immediately and after a one-season recovery period by simultaneously subjecting them to six depths of sand burial and three rainfall regimes.…”

“…Moss crusts are typically in the highest and latest successional stage among surface-dwelling cryptogams, such as cyanobacteria, green algae, and lichen. They also have a greater ability to maintain and enhance the stability and fertility of many arid and semiarid desert ecosystems (Jia et al, 2018;Kidron and Benenson, 2014;Kidron et al, 2010). Recently, moss crusts have attracted the attention of biologists, ecologists and hydrologists (Weber et al, 2016), and it is increasingly accepted that water acquisition plays a critical role in their survival and ecological performances in water-limited arid areas.…”

“…Sand burial is a common disturbance encountered by moss crusts in many desert areas because they are small in size and inhabit the soil surface (Jia et al, 2008(Jia et al, , 2014(Jia et al, , 2018. Sand burial can change WR-related soil temperature, moisture, and nutrients in the micro-environment (Jia et al, 2008(Jia et al, , 2014Maun, 1998Maun, , 2008.…”

“…Sand burial can change WR-related soil temperature, moisture, and nutrients in the micro-environment (Jia et al, 2008(Jia et al, , 2014Maun, 1998Maun, , 2008. It can also change the physiology and growth of moss crusts (Jia et al, 2008(Jia et al, , 2014(Jia et al, , 2018. Therefore, it is important to assess and quantify the influence of sand burial on moss crusts WR, while, up to date, little information is available regarding the effect of sand burial on moss crust WR in desert areas.…”