Agriculture, Ecosystems and Environment

1 Interactive effects of large herbivores and plant diversity on insectabundance in a meadow steppe in ChinaHui Zhua,b,c, Deli Wanga,*, Qinfeng Guod, Jun Liua, Ling WangaaInstitute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, Jilin 130024, ChinabSchool of Life Sciences, Northeast Normal University, Changchun, Jilin 130024, ChinacJilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, Jilin 130024, ChinadUSDA FS, Eastern Forest Environmental Threat Assessment Center, Asheville, NC 28804, USAA R T I C L E I N F OArticle history:Received 15 March 2015 Received in revised form 6 July 2015 Accepted 13 July 2015 Available online 31 July 2015 Keywords:GrasslandLarge herbivore grazingInsect abundancePlant Shannon Wiener indexOrder- and species-levelA B S T R A C TThe structure and dynamics of insect community in grasslands can be influenced by grazing managementvia altered characteristics of plant community.

2 However, attempts to better understand the complexrelationships among plants, insects, and large herbivores is still hampered largely by the interactiveeffects of plants, insects, and large grazers on each other. In this study, we test the hypothesis that theeffect of large herbivores on insect abundance is grazer species-specific and pre-grazing plant diversity-dependent using an experiment with manipulating four grazing treatments ( , control, cattle, goats,and sheep) at low, intermediate, and high plant diversity levels in a meadow steppe at northeast in show that grazing significantly increased the abundance of the entire insect community. Theabundance of each insect order responded differently to grazing treatments, with higher abundance ofOrthoptera and Homoptera under sheep grazing, enhanced abundance of Coleoptera and Diptera undercattle grazing, and reduced Hemiptera abundance, but greater abundance of Lepidoptera under goatsgrazing.

3 Thus different treatments profoundly changed insect taxonomic composition. The six mostdominant species (Euchorthippus unicolor, Aelia nasuta, Trigonotylus ruficornis, Curculionidae sp.,Coccinula quatuordecimpustulata, and Cicadellidae sp.) responded differently to grazing by largeherbivores, with either increased or decreased its abundance. The effects of grazing on insect abundancewere driven by their differential responsive mechanisms for vegetation. More importantly, the effects ofgrazing on insect abundance at both order- and species-levels potentially depended on plant diversitylevels of pre-grazing. Our results suggest that different herbivore species should be used in thebackground of different plant communities for better conservation of insect community in managedgrassland.

4 2015 Elsevier All rights IntroductionInsects are a major but often under-appreciated component ofterrestrial Ecosystems (Belovsky and Slade, 2000; Bronstein et al.,2006; Matt and Charlton, 2006). However, growing evidenceshows that insects are also experiencing local/regional species lossor even global extinction (Collinge, 2000), and that the diversity ofinsects apparently declines even more rapidly than that ofvertebrates and plants (Thomas et al., 2004). Therefore, under-standing critical factors that determine their diversity and speciescomposition becomes an urgent task facing ecologists andconservation biologists. Although many studies have identified arange of management factors that could contribute to changes ininsect communities in grassland Ecosystems (Kruess andTscharntke, 2002a; Bat ry et al.)

5 , 2010), there is a need to integratethese knowledge into predictive and adaptive ongoing manage-ment grazing is a key management tool in grasslands, andits widespread prevalence has generated great interest inunderstanding its ecological effects, especially for insects. Previousstudies show that grazing managements in grasslands can lead toeither lower (Gonzalez-Megias et al., 2004; Joern, 2005; Little-wood, 2008), or higher insect abundance and richness (Cagnoloet al., 2002; Ryder et al., 2005; Debano, 2006; Rosa-Garc a et al.,2009). Such conflicting results might partly derive from thedifference in grazing intensity (Kruess and Tscharntke, 2002b;Cease et al., 2012), grazing season (Fonderflick et al.

6 , 2014), andgrazer species (Dolek and Geyer, 2002). Surprisingly, while most* Corresponding author. Tel.: +86 431 address: (D. Wang). 2015 Elsevier All rights , Ecosystems and Environment 212 (2015) 245 252 Contents lists available at ScienceDirectAgriculture, Ecosystems and Environmentjournal homepage: /ageeefforts have been devoted to the effects of grazing intensity oninsect community, little attention has been given the effects ofgrazer species (J uregui et al., 2008). Different large herbivorespecies may alter vegetation features due to diet selection andbody size, potentially influencing insect community, becausegrazing affect insect community through modifying plant com-munities (Kruess and Tscharntke, 2002b; Jonas and Joern, 2007;Zhu et al.

7 , 2012; van Klink et al., 2015). Therefore, the resulting species-specific of grazing management difficultly renders thedevelopment and application of general management principlesfor biological resources for herbivores are heterogeneously distributedin most grasslands (Li and Reynolds, 1995; Wang et al., 2014), theresponses of plant community to large herbivores strongly dependon the distribution of plant resources before grazing (Palmer et al.,2003; Bakker et al., 2006). The difference in plant species diversityis a typically important characteristic of heterogeneity, and diverseplant communities can markedly affect foraging strategies of largeherbivores and their concomitant impacts on the dynamics ofvegetation itself (Bergvall et al.

8 , 2006; Miller et al., 2007; Wanget al., 2011). Our previous work found that complex spatialneighborhood of several plant species makes the palatable speciesfor herbivores to less selected, contributing to the maintenance ofplant diversity (Wang et al., 2010). This plant species diversitydisaffinity may be an important factor influencing subsequentherbivores impacts on plant community, which, in turn, conse-quently impacts insect community. Therefore, understanding theeffects of grazing by large herbivores on insect community willrequire explicit knowledge of pre-grazing plant diversity previous experimental efforts at the same grassland mainlyfocus on the treatment effects on diversity.

9 Zhu et al. (2012)showed that large herbivores strongly affected insect speciesrichness by modifying plant structural heterogeneity, whichreversed the positive relationship between plant and insectdiversity. Zhong et al. (2014) found that the positive interactionsbetween large herbivores and grasshoppers were driven bydifferential herbivore foraging preferences for plant resourcesthat break down the associational plant defense between grassesand forbs. In contrast, the main goal of this study is to test theeffects of different large herbivore species on insect abundance atdifferent plant diversity levels. Although most extensive researchon the effects of livestock grazing on grassland insect abundancehas taken place, and has provided valuable insights (Littlewood,2008; Cease et al.)

10 , 2012), several important gaps in our knowledgeremain. Because not all species are sensitive to grazing, and the useof taxonomic hierarchies such as order and species levels could beadvantageous in biodiversity assessments (Williams and Gaston,1994). Thus, there is a pressing need for studies that examine howinsect community responds to livestock grazing at taxonomiccomposition. In this study, as part of a previous, targetedexperiment to identify multiple species interactions (plants,insects, and large herbivores) under large herbivore grazing atdifferent plant diversity levels, we examined that the responses ofinsect abundance at both order- and species-levels to theinteractive effects of large herbivore grazing and plant diversityof pre-grazing.