Fig 1.
Surface litter of the fog-adapted grass, S. sabulicola, is colonized by fungi.
Living perennial plant with golden-yellow senescent stems (standing litter) and wind-blown detritus (fine grey surface litter) (1a); fog moisture precipitates on the entire length of the grooved upright stems and may be funnelled to the roots (1b); moisture also collects on leaning grass stems and inflorescences and drips to the sand surface where it can be consumed by beetles and reptiles (1c). Even in the absence of rain events, standing senescent stems and inflorescence litter changes color from golden-yellow (1d), to deep grey (1e). Wetting the grey litter, intended to simulate precipitating fog, resulted in visible fungal growth and spore production within 6 hours (1f).
Fig 2.
Termites (Psammotermes allocerus) consume fungal-colonized litter.
Perennial Stipagrostis ciliata litter with termite casts intact (2a). Termite cast has been removed, showing termites (arrows) stripping the grey outer layer, leaving the golden-yellow interior (2b). Note the small remaining portion of grey litter in the upper center. Standing litter from 2a with cast removed showing that all grey outer surface has been stripped by termites inside the cast (2c). Examples of S. sabulicola stem litter used in the C/N analysis (2d): grey litter (upper right) was compared with golden-yellow stripped material (left and bottom) from inside termite casts and golden-yellow standing litter as seen in Fig 1A.
Table 1.
Surface moisture availability at Gobabeb Research and Training Centre, Namib Desert.
Fig 3.
Rapid respiratory response to wetting of colonized litter.
Respiration response of moistened grey S. sabulicola standing litter over ten hours. An initial reading of the dried material was taken prior to time 0, when the material was visibly moistened by spraying (n = 10, error bars = 1 SE).
Fig 4.
Fungal growth and sporulation on S. sabulicola litter.
Fungal hyphae growing on S. sabulicola substrates after 10 hours incubation (4a: 20x magnification, 4b: 400x magnification).
Fig 5.
Litter respiration declines with drying.
Respiration fluxes fall linearly as litter dries (n = 10, error bars = 1 SE).
Fig 6.
Fungicide suppresses litter respiratory response to wetting.
Respiration response of litter moistened twice with water, with drying after initial wetting (“H20 initial” and “H2O final”); compared to response of litter moistened initially with water (“Captan Initial”) followed by wetting with Captan solution (“Captan Final”). The responses of the first three treatments are not significantly different from one another, but are significantly different from the Captan treatment (p<0.001). (n = 5, error bars = 1 SE).
Table 2.
Stipagrostis sabulicola litter fungal taxa and traits.
Fig 7.
Diel thermal cycles induce fungal growth rings in culture.
Chaetomium strumarium grown in the dark at optimal growth temperature (40⁰C) (7a); and with Namib diel sand-surface thermal cycle (15–50⁰C) (7b): 1 hour increments of increasing temperature from 20–45°C, 50°C for 5 hours, 1-hour increments of decreasing temperature from 45–25°C, and 20°C for 6 hours.
Fig 8.
Fungal colonization enriches nitrogen content of colonized surface litter (NS) relative to that of uncolonized golden-yellow litter (C) and litter remaining after grey surface is stripped by termites (S).
C/N ratios (8a) and %C (8b) of colonized litter were significantly lower than that of uncolonized and stripped litter. %N of colonized litter was significantly higher than that of uncolonized and stripped litter (n = 5; error bars = 1 SE; p<0.001).