.|  Baltimore Ecosystem Study
Invasive soil fauna and biogeochemical cycling

Porcellio scaber, a common introduced isopod. Photo: Katy Juhaszova
Soil invertebrates are known to greatly influence the rate and pathways of microbial decomposition. We are looking at how native and non-native soil invertebrates affect decomposition and nutrient cycling in anthropogenic environments. We are focusing on species level processes instead of the traditional functional groupings, because different species have different natural histories. In addition to gaining insight into the functioning of urban soil communities, such studies also address “redundancy” in soil communities; a fundamental question in ecology and conservation biology.
We have measured potential N-mineralization and nitrification rates in the presence of earthworms (three species one native and two introduced) and terrestrial isopods (six species, all introduced). In the earthworm study the Asian Amynthas hilgendorfi had the largest impact on N-cycling processes, while there was no difference between the native Eisenoides loennbergi and the European Lumbricus terrestris. In contrast, incubation experiments with six terrestrial isopod species resulted in net immobilization (see figure). The overall effect was the same, but the rates were different among the species. Our results point to strong species effects, which have to be taken into account when different microhabitats are invaded by different species.

Potential N mineralization rates of soil in the presence (blue colors) and absence (brown) of six terrestrial isopod species.
Earthworms are ecosystem engineers, thus major shifts in earthworm community composition and abundance fundamentally alters the soil ecosystem. Soil organic matter and associated litter represents the largest actively cycling pool of organic carbon. Our studies address invasive earthworm effects on aspects of soil carbon cycling, including soil CO2 efflux, plant biopolymer alteration, and soil organic matter stabilization.
Ma, Y TR Filley, CT Johnston, SE Crow, K Szlavecz, MK McCormick 2013. The combined controls of land use legacy and earthworm activity on soil organic matter chemistry and particle association during afforestation. Org. Geochem. http://dx.doi.org/10.1016/j.orggeochem.2013.02.010
Zicsi A, Szlavecz K, Csuzdi Cs. 2011. Leaf litter acceptance and cast deposition by peregrine and endemic European lumbricids (Oligochaeta: Lumbricidae). Pedobiologia doi:10.1016/j.pedobi.2011.09.004
Xia, L, Szlavecz K, Swan C, Burgess JL. 2011. Inter- and intra-specific interactions of epigeic and endogeic earthworms and the implication for C cycling. Soil Biology and Biochemistry 43: 1584-1590.
Crow SE, TR Filley, M McCormick, K Szlavecz, DE Stott, D Gamblin, G Conyers 2009: Invasive earthworm feeding and forest succession interact to influence particulate organic matter chemistry in the soil. Biogeochemistry 92: 61-82
Kathy Szlavecz (Johns Hopkins University)
Peter Groffman (Cary Institute of Ecosystem Studies)
Richard Pouyat (USDA Forest Service)
Csaba Csuzdi (Hungarian Natural History Museum)
Ian Yesilonis (USDA Forest Service)
Sarah Placella (JHU Senior Thesis)
Kim Townsend (JHU)
Katarina Juhaszova (JHU REU project)