English Ivy (Hedera helix) is fast, but ash (Fraxinus excelsior) too: Decomposition of English Ivy litter compared to four common host trees - A multisite citizen sciences project

Abstract

English Ivy (Herdera helix, Araliaceae) is an evergreen woody climbing plant occurring naturally in temperate forests of Europe and as introduced ornamental plant in many parts of the world, becoming invasive in some. Over the last decades an increase of ivy occurrence in middle Europe was observed in forests as well as in urban or rural areas. As a consequence, ivy might also play a larger role in food webs and nutrient and carbon cycling in the future. We followed the decomposition of litter of ivy and compared it to litter of four common host trees species (sycamore, ash, oak, beech) using mesh bags with and without mesofauna access over a period of 10 months. Experiments were set up in nine gardens spread over Germany, involving citizen scientists. In the presence of mesofauna, ivy litter decomposed faster than litter of three of the tree species. The contribution of mesofauna to decomposition followed a similar pattern. In the absence of mesofauna, ivy decomposed faster than two of the tree species. In a changing world where ivy becomes more abundant, and tree species face population decline due to disease or climatic stress, litter composition will also change. Ivy adds medium to fast decaying litter to the ecosystem, and in other seasons than tree species. Conducting experiments with citizen scientist offers the possibility for wide-spread multi-site experiments generating robust data and overcoming local restrictions with low budgets.