Earthworm selection of Short Rotation Forestry leaf litter assessed through preference testing and direct observation

Short Rotation Forestry (SRF) practice which includes use of rapidly growing native and non-native tree species has been introduced to the UK as a method to increase woody biomass production. A largely unknown aspect of SRF is the quality of leaf litter, and its palatability to the soil decomposer community of which earthworms are a major component. The aims of the present study were to investigate and compare the preference of selected native British earthworms for selected SRF species litter. These were addressed through a series of controlled laboratory experiments. Choice chambers were used to quantify litter removal by Allolobophora chlorotica, Aporrectodea caliginosa, Aporrectodea longa and Lumbricus terrestris over a period up to five weeks. In addition, an infrared webcam recording technique was used to directly observe litter selection behaviour of L. terrestris under cover of darkness. Choice chamber experiments revealed that earthworms significantly preferred (p < 0.05) leaf litter of native alder (Alnus glutinosa), ash (Fraxinus excelsior) and birch (Betula pendula) over non-native eucalyptus (Eucalyptus nitens), sweet chestnut (Castanea sativa) and sycamore (Acer pseudoplatanus). Sweet chestnut litter was the least preferred by all selected earthworms. Webcam results revealed that L. terrestris demonstrates clear leaf litter selection behaviour and it was not a random activity. Direct webcam observation results corroborated the results of choice chamber experiments.