Species identity influences belowground arthropod assemblages via functional traits

Research Article Courtney E. Gorman*, Quentin D. Read, Michael E. Van Nuland, Jessica A. M. Bryant, Jessica N. Welch, Joseph T. Altobelli, Morgan J. Douglas, Mark A. Genung, Elliot N. Haag, Devin N. Jones, Hannah E. Long, Adam D. Wilburn, Jennifer A. Schweitzer and Joseph K. Bailey Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996, USA Received: 14 August 2013; Accepted: 17 October 2013; Published: 31 October 2013 Citation: Gorman CE, Read QD, Van Nuland ME, Bryant JAM, Welch JN, Altobelli JT, Douglas MJ, Genung MA, Haag EN, Jones DN, Long HE, Wilburn AD, Schweitzer JA, Bailey JK. 2013. Species identity influences belowground arthropod assemblages via functional traits. AoB PLANTS 5: plt049; doi:10.1093/aobpla/plt049 Abstract. Plant species influence belowground communities in a variety of ways, ultimately impacting nutrient cycling. Functional plant traits provide a means whereby species identity can influence belowground community interactions, but little work has examined whether species identity influences belowground community processes when correcting for evolutionary history. Specifically, we hypothesized that closely related species would exhibit (i) more similar leaf and root functional traits than more distantly related species, and (ii) more similar associated soil arthropod communities. We found that after correcting for evolutionary history, tree species identity influenced belowground arthropod communities through plant functional traits. These data suggest that plant species structure may be an important predictor in shaping associated soil arthropod communities and further suggest the importance of better understanding the extended consequences of evolutionary history on ecological processes, as similarity in traits may not always reflect similar ecology. Keywords: Belowground processes; community similarity; functional plant traits; soil macroinvertebrates; soils; species identity. Introduction Global biodiversity loss is occurring at unprecedented rates (Pimm et al. 1995; Sala et al. 2000) in response to a variety of human alterations to the environment (Vitousek 1994; Vitousek et al. 1997; Chapin et al. 2000), making understanding the consequences of such loss on community and ecosystem function a top priority. Much attention has been given to understanding the effects of biodiversity aboveground, with particular emphasis on the relationship between species diversity and primary productivity (Tilman 1996; Hooper and Vitousek 1997; Hector et al. 1999; Tilman et al. 2001). While these studies have undeniably improved our understanding of the effects of biodiversity, it is equally important to consider how aboveground biodiversity affects the diversity and function of belowground communities, and to understand how above- and belowground communities interact to influence community and ecosystem processes. Interest in the effects of plant species diversity on belowground soil organisms and the soil food web is growing (Kowalchuk et al. 2002; Wardle et al. 2003; De Deyn et al. 2004; Eisenhauer et al. 2010); however, the interactions among plant species identity and diversity and belowground Species identity influences belowground arthropod assemblages via functional traits * Corresponding author’s e-mail address: Published by Oxford University Press on behalf of the Annals of Botany Company. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/ licenses/by/3.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. AoB PLANTS www.aobplants.oxfordjournals.org & The Authors 2013 1 Gorman et al. — Species identity influences belowground arthropod communities 2 AoB PLANTS www.aobplants.oxfordjournals.org belowground arthropod communities via functional similarity. We speculate that phylogenetic conservatism of functional traits may be playing a role in determining belowground arthropod community assemblages. Methods Study site and field sampling To determine whether tree species identity governs functional traits and associated belowground community composition, we studied monocultures of five tree species located at Norris Dam State Park, Tennessee, USA (36.239608N, 84.109448W). On a floodplain adjoining the Clinch River, the Tennessee Valley Authority (TVA) previously established experimental forestry plots of several native trees for a hardwood tree improvement programme in the 1960s (specific details unknown by TVA). The plots consisted of 25–50 trees per species with trees spaced equally every 3 m; additional woody species were not present in the plots. Plots are underlain by cherty silt loam (Natural Resources Conservation Service (NRCS) Web Soil Survey) and are arranged randomly along the adjacent riparian area (45 m from the river). The tree species we sampled included Quercus alba (white oak), Quercus prinus (chestnut oak), Juglans nigra (black walnut), Ilex opaca (American holly) and Liriodendron tulipifera (tulip-poplar). These species represent three plant orders (Magnoliales, Fagales and Aquifoliales) and four families (Aquifoliaceae, Fagaceae, Juglandaceae and Magnoliaceae) with varying degrees of relatedness. Plant functional traits and soil communities and processes To examine the hypothesis that after correcting for evolutionary history, more closely related tree species had similar functional traits and soil communities, five randomly chosen individual trees were sampled from each plot. Three randomly selected and fully expanded leaves from terminal shoots at the mid-canopy level were collected with pole pruners, and 25 cm of root within a 50-cm radius around each tree were collected and stored at 4 8C until analysis. We measured two different functional traits: specific leaf area (SLA) and specific root area (SRA). Specific leaf area is an indicator of potential relative growth rate, gives an indication of investment in leaf structural defence, and typically correlates positively with resource availability (Cornelissen et al. 2003). Specific root area is strongly correlated with absorptive activity by the root biomass (Cornelissen et al. 2003). To determine SLA (foliar area : mass ratio), leaf area was measured via WinFOLIA (Regent Instruments, Toronto, Canada) and leaves were oven dried at 70 8F for 48 h and the oven-dried leaf mass was recorded. To determine SRA, roots were & The Authors 2013 communities are not well understood (Wardle 2002; Hooper et al. 2005). Plant species influence belowground communities in a variety of ways including the amount of organic matter returned to the soil and the chemical composition of litter (Wardle 2002; Wardle et al. 2004), ultimately impacting nutrient cycling. Further understanding of the relationships between species identity and diversity aboveground and community properties and p (...truncated)