Lumbricus terrestris L. distribution within an experimental humus mosaic in a mountain spruce forest

Abstract

An experiment was designed at a mountain site to study the distribution of adult Lumbricus terrestris in relation to a small-scale mosaic of humus forms representative of different stages of a spruce forest ecosystem. Good agreement was found between distribution in the mosaic and that in the field. ANOVA tests demonstrated the strong influence of humus form on earthworm abundance when comparing a vermimull (high earthworm burrowing activity) taken from a spruce regeneration site (61.8 individuals m ). The same pattern was found with individual biomass, but with lower significance. Main differences observed in the experimental design were attributed to the immediate carrying density of the humus forms. A distinction was made between humus profiles built up with or without spruce cover. In the latter case (regeneration site and bilberry heath), the immediate carrying capacity indicated by the experimental approach overestimated the field density by a factor of 4. Under spruce this overestimate was even higher (approximately 10 times too high in an adult spruce stand (160 years old) and 30 times too high under moss cover). The increase in density due to experimental conditions was not determined for leptomoder humus accumulated under the actively growing spruce stand (60 years old) since the earthworm density was near zero in both cases. Relationships between humus form and earthworm populations are discussed.

Acid-tolerant Collembola cannot colonize metal-polluted soils at neutral pH

“…In the presence of predators, the absence of any significant change in the collembolan population (apart from the disappearance of rare species, which is expected in microcosms) was indicative of an equilibrium condition. The disappearance of most introduced specimens could be due to saturation of the original population (Longstaff, 1976;Bernier and Ponge, 1998;Winkler and Kampichler, 2000) or to unfavourable food and environmental conditions. The first cause can be ruled out, given the abundance of food (decaying roots, fungi, humus) present in the sampled holorganic profiles, as ascertained from direct observation and from quantitative analyses (Gillet and Ponge, 2002).…”

Explaining density‐dependent regulation in earthworm populations using life‐history analysis

“…The high density patches consisted mostly of juveniles and sub‐adults, but there were also a fair number of adults recorded. Bernier and Ponge (1998) reported densities ranging from 1 to 3 worms per l in a mountain spruce stand. Also Bengtsson et al (1983) studied the density of L. terrestris in forest soils.…”

“…The observation of Nicholsonian density dependence in L. terrestris at densities representative for field populations (e.g. based on the data of Daniel 1992, Bernier and Ponge 1998), does not necessarily mean that this is an important population regulation mechanism. Instead, such effects should be considered in their biological context.…”