Linking abundances of the dung fungus Sporormiella to the density of bison: implications for assessing grazing by megaherbivores in palaeorecords. (26th July 2013)

• Record Type: Journal Article
• Authors: Gill, Jacquelyn L.; McLauchlan, Kendra K.; Skibbe, Adam M.; Goring, Simon; Zirbel, Chad R.; Williams, John W.; Wilson, Scott
• Is Part Of: Journal of ecology. Volume 101:Number 5(2013:Sep.)
• Page Start: 1125
• Page End: 1136
• Publication Date: 2013-07-26
• Subjects: Plant ecology -- Periodicals; 577.05
• DOI: 10.1111/1365-2745.12130
• Languages: English
• ISSNs: 0022-0477

Abstract

<abstract abstract-type="main" id="jec12130-abs-0001"> <title>Summary</title> <p> <list id="jec12130-list-0001" list-type="order"> <list-item> <p>Megaherbivores likely had important influences on past vegetation dynamics, just as they do in modern ecosystems. The exact nature of megaherbivores' role can be studied using a relatively new suite of palaeoecological techniques, including the quantification of fossil spores from <italic>Sporormiella</italic> and other coprophilous fungi as indicators of megafaunal biomass in sediment records. However, a quantitative linkage of spore abundance with megaherbivore biomass or grazing intensity has been lacking.</p> </list-item> <list-item> <p>Konza Prairie Biological Station (Kansas, USA), located in the midcontinent of North America, contains native tallgrass prairie grazed by a herd of bison (<italic>Bison bison</italic>) in a 1000‐ha enclosure, providing an excellent opportunity to test the effects of megaherbivores on grassland community composition and their potential signature in the palynological record. We collected pollen and spores during 2009 and 2010 from a network of 28 modified Tauber traps. The precise locations of the bison herd were recorded using GPS collars; we calculated bison grazing intensity (kg m<sup>−2</sup> year<sup>−1</sup>) to high spatial precision within concentric circles around each trap (radii from 25 to 500 m).</p> </list-item> <list-item> <p>Both relative (per cent) and absolute (concentration) abundances of <italic>Sporormiella</italic> were significantly higher in traps inside the enclosure and were positively correlated with bison grazing intensity. The cut‐off for distinguishing between bison‐grazed and ungrazed traps was determined to be 2.8% <italic>Sporormiella</italic> of the total pollen and spore sum, consistent with previous palaeoecological reconstructions. The relationship between <italic>Sporormiella</italic> abundances and available grazing area around each trap was strongest at short radii (25–100 m), suggesting that spores do not disperse far from their source. <italic>Sporormiella</italic> should thus be considered a local‐scale indicator of megaherbivore presence.</p> </list-item> <list-item> <p>Traps in the grazed area had significantly higher percentages of <italic>Ambrosia</italic> and lower percentages of Poaceae pollen than traps from ungrazed areas. This suggests that the pollen record has the potential to detect the ecological effects of bison grazing on grassland community composition.</p> </list-item> <list-item> <p> <italic>Synthesis</italic>. This study refines the use of <italic>Sporormiella</italic> as a proxy for local megaherbivore presence, especially in grassland systems. Multiproxy <italic>Sporormiella</italic> and pollen analyses may help elucidate the past drivers of grassland dynamics, including the possible role of bison in mediating grass–forb interactions during the variable moisture regimes of the last 12, 000 years.</p> </list-item> </list> </p> </abstract>