title: Non-rainfall moisture activates fungal decomposition of surface litter in the Namib Sand Sea.
abstract: The hyper-arid western Namib Sand Sea (mean annual rainfall 0-17 mm) is a detritus-based ecosystem in which primary production is driven by large, but infrequent rainfall events. A diverse Namib detritivore community is sustained by minimal moisture inputs from rain and fog. The decomposition of plant material in the Namib Sand Sea (NSS) has long been assumed to be the province of these detritivores, with beetles and termites alone accounting for the majority of litter losses. We have found that a mesophilic Ascomycete community, which responds within minutes to moisture availability, is present on litter of the perennial Namib dune grass Stipagrostis sabulicola. Important fungal traits that allow survival and decomposition in this hyper-arid environment with intense desiccation, temperature and UV radiation stress are darkly-pigmented hyphae, a thermal range that includes the relatively low temperature experienced during fog and dew, and an ability to survive daily thermal and desiccation stress at temperatures as high as 50°C for five hours. While rainfall is very limited in this area, fog and high humidity provide regular periods (≥ 1 hour) of sufficient moisture that can wet substrates and hence allow fungal growth on average every 3 days. Furthermore, these fungi reduce the C/N ratio of the litter by a factor of two and thus detritivores, like the termite Psammotermes allocerus, favor fungal-infected litter parts. Our studies show that despite the hyper-aridity of the NSS, fungi are a key component of energy flow and biogeochemical cycling that should be accounted for in models addressing how the NSS ecosystem will respond to projected climate changes which may alter precipitation, dew and fog regimes.
authors.affiliation: Biology Department, Grinnell College, Grinnell, Iowa, United States of America.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Jacobson
authors.affiliation: CBS-KNAW Fungal Biodiversity Centre, Utrecht, The Netherlands.
authors.forename: Anne
authors.initials: A
authors.lastname: van Diepeningen
authors.affiliation: Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, United States of America.
authors.forename: Sarah
authors.initials: S
authors.lastname: Evans
authors.affiliation: Biology Department, Grinnell College, Grinnell, Iowa, United States of America.
authors.forename: Rachel
authors.initials: R
authors.lastname: Fritts
authors.affiliation: Biology Department, Grinnell College, Grinnell, Iowa, United States of America.
authors.forename: Philipp
authors.initials: P
authors.lastname: Gemmel
authors.affiliation: Biology Department, Grinnell College, Grinnell, Iowa, United States of America.
authors.forename: Chris
authors.initials: C
authors.lastname: Marsho
authors.affiliation: Gobabeb Research and Training Centre, Gobabeb, Namibia.
authors.forename: Mary
authors.initials: M
authors.lastname: Seely
authors.affiliation: Biology Department, Grinnell College, Grinnell, Iowa, United States of America.
authors.forename: Anthony
authors.initials: A
authors.lastname: Wenndt
authors.affiliation: Biology Department, Grinnell College, Grinnell, Iowa, United States of America.
authors.forename: Xiaoxuan
authors.initials: X
authors.lastname: Yang
authors.affiliation: Biology Department, Grinnell College, Grinnell, Iowa, United States of America.
authors.forename: Peter
authors.initials: P
authors.lastname: Jacobson
mesh_terms: D003889:Desert Climate; D017753:Ecosystem; D005658:Fungi / Q000378:metabolism*; D005659:Fungicides, Industrial / Q000494:pharmacology; D006109:Poaceae / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
chemical_list: D005659:Fungicides, Industrial; D014867:Water