A temperature-driven shift in soil detritivore community dynamics could hold significant consequences for carbon flux and nutrient cycling in temperate forest ecosystems

Project Overview
<p>Elevated temperature caused by anthropogenic greenhouse gas emissions may exacerbate climate change via a positive feedback from increased carbon dioxide (CO2) released as a product of soil microbial respiration [1]. Soil invertebrates (earthworms, insects, millipedes, etc.) directly and indirectly affect microbes and vital ecosystem processes like nutrient uptake and losses [2]. However, invertebrates are ignored in climate models [2]. Soil macroinvertebrates including detritivores (litter shredders and burrowers) modify soil properties, food availability and habitat for microbes, but exhibit physiological and behavioral changes in response to heat stress [3,4]. Thus, interactions among these taxa, and consequently elements of nutrient cycling, and CO2 emissions via respiration, may be altered under elevated temperatures [5,6]. Therefore, it is critical to measure the response of macroinvertebrates to climate change variables to better understand how soil C stocks will respond to warming. This project will enhance knowledge by experimentally manipulating temperature and macroinvertebrate composition to subsequently measure C and nitrogen (N) retention and losses from forest floors.</p><p>I will construct mesocosms representative of forest floor components that will be placed in two warming scenarios (+0&deg;C, +5&deg;C) and contain different combinations of three detritivores including two earthworms <em>L. terrestris </em>and <em>L. rubellus</em>, and a common millipede <em>N. americanus</em>. A Simplex design based on biomass will allow me to parse out the isolated and interactive effects of warming and invertebrate interactions [5]. Specifically, I am interested in how species-specific functional traits will contribute to individual fitness, ecosystem effects (soil C/N retention, CO2 emissions, leaching), and microbe biomass/community composition.</p><p>I expect biomass to increase in earthworms and decrease in millipedes due to the increased ability of earthworms to buffer themselves against the effects of temperature via deep burrowing. This will allow earthworm traits and effects on ecosystem processes to overwhelm those of millipedes [6]. I predict increased C flux, decomposition rate, and fragmentation under elevated temperatures as the consumptive activity of these organisms and microbes increases with temperature [3,4]. I expect soil C and N to decrease and N leaching to increase, in response to the interactive effect of earthworms and temperature [7]. I predict an increase in bacteria to fungi ratio due to bioturbation and consumptive effects of both species [8].</p><p>1 Melillo, J.M., et al. Science 298.5601 (2002) 2173-2176</p><p>2 Lavelle, Patrick, et al. Eur J Soil Biol 42 (2006): S3-S15</p><p>3 Ott, D., et al. Philos T R Soc B 367.1605 (2012): 3025-3032</p><p>4 Uvarov, A.V., et al. Soil Biol Biochem 43.3 (2011): 559-570</p><p>5 Andriuzzi, W.S., et al. 50.6 Appl Soil Ecol (2015)</p><p>6 Snyder, B.A., et al. Soil Biol Biochem 57 (2013): 212-216</p><p>7 Ewing, H.A., et al. Ecosystems 18.2 (2015) 328-342</p><p>8 Dempsey, M.A., Soil Biol Biochem 43.10 (2011) 2135-2141</p>
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