Deer, invasive plants, and earthworms: interactions and ecosystem consequences
White-tailed deer, invasive plants, and exotic earthworms are major players in shaping ecosystem processes and plant and animal communities in eastern forests. We set out to understand whether deer, honeysuckle, and earthworms interact and potential implications of these interactions for carbon and nutrient dynamics.
To do so, we removed both deer and Amur honeysuckle at five sites in the Miami University Natural Areas (southwestern Ohio, USA). The experiment began in the summer of 2010, with sampling beginning the following summer in 2011. We found drastic loss of earthworm populations within deer exclosures relative to deer access plots, suggesting native deer benefit exotic earthworms. Managing for overabundant deer will alleviate negative pressures from exotic earthworms. Publications: Mahon and Crist 2019 |
To test whether changes to exotic earthworm populations resulted in changes to ecosystem function, we placed leaf litter boxes in our experimental plots and used differing mesh sizes to allow and prevent access by earthworms. We found strong indirect controls of white-tailed deer on leaf litter decomposition mediated through changes to earthworm density, but found no difference in microbial decomposition between deer plots. Our findings indicate that deer and earthworms synergistically increase rates of leaf litter decomposition, which has negative implications for seedlings, litter dwelling organisms, and carbon storage potential for eastern deciduous forests. Publications: Mahon et al. 2020 |
Long-term dynamics of forest floor ant communities
Ants are key members of terrestrial ecosystems, acting as predators, seed dispersers, and ecosystem engineers. Changes in ant communities likely has broader effects on ecosystems.
We found increases in ant abundance and richness following deer exclosure. The ant community was also strongly related to litter quantity. Our findings indicate strong effects of herbivores and invasive shrubs on litter-dwelling ants, mediated through changes in litter quantity and vegetation structure. We also found the strength of deer and honeysuckle treatment effects were dependent on the abundance of individual ant species, with more abundant species more sensitive to experimental treatments. These findings indicate drivers of ecosystem change may affect numerically dominant ant species more than less common ant species. Publications: Mahon et al. 2019 |