TY - JOUR

T1 - Drivers of earthworm incidence and abundance across European forests

AU - Wandeler, Hans De

AU - Sousa-Silva, Rita

AU - Ampoorter, Evy

AU - Bruelheide, Helge

AU - Carnol, Monique

AU - Dawud, Seid Muhie

AU - Danila, Gabriel

AU - Finér, Leena

AU - Hättenschwiler, Stephan

AU - Hermy, Martin

AU - Jaroszewicz, Bogdan

AU - Joly, Francois-Xavier

AU - Müller, Sandra

AU - Pollastrini, Martina

AU - Ratcliffe, Sophia

AU - Raulund-Rasmussen, Karsten

AU - Selvi, Federico

AU - Valladares, Fernando

AU - Van Meerbeck, Koenraad

AU - Verheyen, Kris

AU - Vesterdal, Lars

AU - Muys, Bart

PY - 2016

Y1 - 2016

N2 - Earthworms have a significant influence on the structure, composition and functioning of forest ecosystems,but in spite of their role as ecosystem engineers, little is known on the factors controlling theirdistribution across European forests. Optimised sampling techniques, as well as more advanced statisticaltools and geographical information systems have facilitated studies at the landscape scale. But these,and even larger-scale studies, are scarce due to data limitations, taxonomic inconsistencies and practicalissues in linking existing databases. In this continental-scale field-based study we used boostedregression tree modelling to identify and evaluate the relative importance of environmental factorsexplaining earthworm incidence (presence/absence) and abundance (density and biomass) in Europeanforests. To parameterise our models earthworms were sampled in six forest landscapes along a latitudinalgradient from the boreal north to the Mediterranean south in spring or autumn of 2012, togetherwith several environmental variables. Earthworms were sampled using a combined method of mustardextraction and hand sorting of litter and a soil monolith, after which they were weighed and identified tofunctional group (epigeic, endogeic and anecic). We found that litter- and soil-related variables bestexplained earthworm incidence and biomass in European forests, leaving only a minor role to climaterelatedvariables. Among the litter related variables, understory vegetation played an important role inexplaining earthworm incidence and abundance. The relative importance of explanatory variablesdiffered between models for incidence, density and biomass and between earthworm functional groups.Our results suggested that threshold values for soil C:N ratio, forest floor pH and understory plantbiomass and plant nutrient concentrations have to be attained before earthworms can occur. Beyondthese threshold values, variables like soil C:N ratio, tree litter C:P ratio and forest floor mass further explain earthworm biomass. Mechanisms behind these observations are discussed in the light of future earthworm distribution modelling at continental scale.

AB - Earthworms have a significant influence on the structure, composition and functioning of forest ecosystems,but in spite of their role as ecosystem engineers, little is known on the factors controlling theirdistribution across European forests. Optimised sampling techniques, as well as more advanced statisticaltools and geographical information systems have facilitated studies at the landscape scale. But these,and even larger-scale studies, are scarce due to data limitations, taxonomic inconsistencies and practicalissues in linking existing databases. In this continental-scale field-based study we used boostedregression tree modelling to identify and evaluate the relative importance of environmental factorsexplaining earthworm incidence (presence/absence) and abundance (density and biomass) in Europeanforests. To parameterise our models earthworms were sampled in six forest landscapes along a latitudinalgradient from the boreal north to the Mediterranean south in spring or autumn of 2012, togetherwith several environmental variables. Earthworms were sampled using a combined method of mustardextraction and hand sorting of litter and a soil monolith, after which they were weighed and identified tofunctional group (epigeic, endogeic and anecic). We found that litter- and soil-related variables bestexplained earthworm incidence and biomass in European forests, leaving only a minor role to climaterelatedvariables. Among the litter related variables, understory vegetation played an important role inexplaining earthworm incidence and abundance. The relative importance of explanatory variablesdiffered between models for incidence, density and biomass and between earthworm functional groups.Our results suggested that threshold values for soil C:N ratio, forest floor pH and understory plantbiomass and plant nutrient concentrations have to be attained before earthworms can occur. Beyondthese threshold values, variables like soil C:N ratio, tree litter C:P ratio and forest floor mass further explain earthworm biomass. Mechanisms behind these observations are discussed in the light of future earthworm distribution modelling at continental scale.

U2 - 10.1016/j.soilbio.2016.05.003

DO - 10.1016/j.soilbio.2016.05.003

M3 - Journal article

VL - 99

SP - 167

EP - 178

JO - Soil Biology & Biochemistry

JF - Soil Biology & Biochemistry

SN - 0038-0717

ER -