Change in dominance determines herbivore effects on plant biodiversity
- Authors: Koerner, Sally , Smith, Melinda , Burkepile, Deron , Hanan, Niall , Avolio, Meghan , Collins, Scott , Knapp, Alan , Lemoine, Nathan , Forrestel, Elizabeth , Eby, Stephanie , Thompson, Dave , Aguado-Santacruz, Gerardo , Anderson, John , Anderson, Michael , Angassa, Ayana , Bagchi, Sumanta , Bakker, Elisabeth , Bastin, Gary , Baur, Lauren , Beard, Karen , Beever, Erik , Bohlen, Patrick , Boughton, Elizabeth , Canestro, Don , Cesa, Ariela , Chaneton, Enrique , Cheng, Jimin , D'Antonio, Carla , Deleglise, Claire , Dembele, Fadiala , Dorrough, Josh , Eldridge, David , Fernandez-Going, Barbara , Fernandez-Lugo, Silvia , Fraser, Lauchlan , Freedman, Bill , Garcia-Salgado, Gonzalo , Goheen, Jacob , Guo, Liang , Husheer, Sean , Karembe, Moussa , Knops, Johannes , Kraaij, Tineke , Kulmatiski, Andrew , Kytoviita, Minna-Maarit , Lezama, Felipe , Loucougaray, Gregory , Loydi, Alejandro , Milchunas, Dan , Milton, Suzanne , Morgan, John , Moxham, Claire , Nehring, Kyle , Olff, Han , Palmer, Todd , Rebollo, Salvador , Riginos, Corinna , Risch, Anita , Rueda, Marta , Sankaran, Mahesh , Sasaki, Takehiro , Schoenecker, Kathryn , Schultz, Nick , Schutz, Martin , Schwabe, Angelika , Siebert, Frances , Smit, Christian , Stahlheber, Karen , Storm, Christian , Strong, Dustin , Su, Jishuai , Tiruvaimozhi, Yadugiri , Tyler, Claudia , Val, James , Vandegehuchte, Martijn , Veblen, Kari , Vermeire, Lance , Ward, David , Wu, Jianshuang , Young, Truman , Yu, Qiang , Zelikova, Tamara
- Date: 2018
- Type: Text , Journal article
- Relation: Nature Ecology & Evolution Vol. 2, no. 12 (2018), p. 1925-1932
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- Description: Herbivores alter plant biodiversity (species richness) in many of the world’s ecosystems, but the magnitude and the direction of herbivore effects on biodiversity vary widely within and among ecosystems. One current theory predicts that herbivores enhance plant biodiversity at high productivity but have the opposite effect at low productivity. Yet, empirical support for the importance of site productivity as a mediator of these herbivore impacts is equivocal. Here, we synthesize data from 252 large-herbivore exclusion studies, spanning a 20-fold range in site productivity, to test an alternative hypothesis—that herbivore-induced changes in the competitive environment determine the response of plant biodiversity to herbivory irrespective of productivity. Under this hypothesis, when herbivores reduce the abundance (biomass, cover) of dominant species (for example, because the dominant plant is palatable), additional resources become available to support new species, thereby increasing biodiversity. By contrast, if herbivores promote high dominance by increasing the abundance of herbivory-resistant, unpalatable species, then resource availability for other species decreases reducing biodiversity. We show that herbivore-induced change in dominance, independent of site productivity or precipitation (a proxy for productivity), is the best predictor of herbivore effects on biodiversity in grassland and savannah sites. Given that most herbaceous ecosystems are dominated by one or a few species, altering the competitive environment via herbivores or by other means may be an effective strategy for conserving biodiversity in grasslands and savannahs globally.
The golf ball method for rapid assessment of grassland structure
- Authors: Schultz, Nick , Keatley, Marie , Antos, Mark , Wong, Nathan , Moxham, Claire , Farmilo, Brad , Morgan, John
- Date: 2017
- Type: Text , Journal article
- Relation: Ecological Management and Restoration Vol. 18, no. 2 (2017), p. 134-140
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- Description: A key task for native grassland managers is to assess when biomass reduction is necessary to maintain plant and animal diversity. This requires managers to monitor grassland structure. Parks Victoria and La Trobe University developed a method for rapid assessment of grassland structure using golf balls. Baker-Gabb et al. (Ecological Management & Restoration, 17, 2016, p235) provide an example of where the method has been used to manage grassland structure to favour an endangered bird, the Plains-wanderer (Pedionomus torquatus). In this study, we provide further critical analysis of the method using three data sets collected across different parts of Victoria that relate golf ball scores to various habitat attributes. We demonstrate how the golf ball score provides a good surrogate for key aspects of grassland structure. We show that the method does not provide a reliable surrogate for above-ground biomass or vegetation cover, although we discuss how biomass and cover are not particularly good indicators of grassland structure. We argue that elements of grassland structure may be better correlated with desired conservation outcomes (e.g. plant species diversity or the presence of a particular species) than biomass or cover alone. We discuss examples of how the golf ball method has been used, and how it can be improved. The method will be particularly useful where a link can be demonstrated between golf ball scores and desired conservation outcomes, such as in the case of the Plains-wanderer. © 2017 Ecological Society of Australia and John Wiley & Sons Australia, Ltd