Moisture and substrate stability determine VA-mycorrhizal fungal community distribution and structure in an arid grassland

Jacobson, Kathryn M
Journal of Arid Environments
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The arid central dune field of the Namib Desert is characterized by a pronounced rainfall gradient across its west-east, 160 km breadth, and a correlated increase in sand stability and grass community complexity. In addition to these macro-gradients, micro-gradients of sand stability and available moisture across each dune slope result in stratified grass communities on the dunes. The effects of abiotic factors and plant associations on the community structure of VA-mycorrhizal fungi in a naturally arid and unstable grassland could thus be investigated. Mycorrhizal fungal communities associated with five grass species were sampled at sites located across the gradients. Diversity and abundance of spores, as well as percent mycorrhizal colonization of plant roots were used to characterize the fungal communities and their plant specificity. FiveGlomusspecies (Glomales) were associated with grasses at all sites, but no plant specificity was observed. Rather, the fungal communities varied in diversity and abundance both within a dune site and across the dune field. Regression analyses showed that spore abundance and colonization levels were significantly affected by abiotic factors. Sand stability affected spore abundance and thus determined the limits of distribution of the fungal community in the dune grassland. In contrast, colonization levels were primarily affected by moisture availability, and fungal growth and spore production following an isolated rain event were closely associated with moisture availability. A rapid and opportunistic growth response to moisture, production of resilient spores in response to declining moisture, and lack of plant symbiont specificity are characteristics which allow mycorrhizal fungal communities to function under hyperarid conditions.
Name of Journal: 
Journal of Arid Environments
Resource Type: 
Document Type: 
Journal Issue/Article
Grassland Society of Southern Africa

The Grassland Society of Southern Africa (GSSA) is involved and concerned with the science and practice of range and pasture management. This broad field involves primarily the use and conservation of natural resources. It encompasses applied fields such as livestock production, wildlife management, nature conservation, water catchment management and range and mine-dump rehabilitation. The disciplines include, amongst others, ecology, botany zoology, range and pasture science, animal science, soil science and genetics. This collection includes journal articles from the African Journal of Range and Forage Science as well as related articles and reports from throughout the Southern African region.