Earthworm responses to plant species' loss and elevated CO₂ in calcareous grassland

• Published in: Plant and soil Vol. 208; no. 1; pp. 1 - 8
• Main Authors: Zaller, J.G., Arnone, J.A.
• Format: Journal Article
• Language: English
• Published: Dordrecht Kluwer Academic Publishers 01-01-1999; Springer; Springer Nature B.V
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Biomass; Carbon dioxide; Earthworms; Ecosystem services; Flowers & plants; Fundamental and applied biological sciences. Psychology; Grassland soils; Grasslands; Herbivores; Indigenous plants; Indigenous species; Plant communities; Plant species; Plants; Population ecology; Protozoa. Invertebrata; Soil ecology; Species; Topsoil; Worms; Switzerland; Europe; Grassland; Carbon dioxide; Population structure; Biomass; Biodiversity; Annelida; Oligochaeta; Earthworm; Medium enrichment; Calcareous soils; Animal community; Ecosystem; Allolobophora; Invertebrata; Population density
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/A:1004424720523

The objectives of this study were: (1) to quantify the effects of plant species' loss from designed calcareous grassland communities at a field site in northwestern Switzerland on the size and composition of earthworm communities, and (2) to evaluate how exposure of plant communities to elevated atmospheric CO₂ might alter the effects of plant species' loss on earthworm communities. We non-destructively censused earthworm communities in each of 24 1.2 m² experimental plots in autumn 1996 when soils were wet and earthworms were active. Each plot contained an experimental plant community with 31, 12 or 5 native plant species (eight plots each). Half of the plots in each species treatment were exposed to ambient CO₂ concentrations (350 µL CO₂ L⁻¹) and half to elevated CO₂ (600 µL CO₂ L⁻¹) using screen-aided CO₂ control. The study was conducted in the fourth year after community establishment and the third year of CO₂ treatment as part of a long-term study on the interactive effects of plant species' loss and elevated CO₂ on grassland communities. The size (density and biomass) of earthworm communities declined linearly when the number of plant species in the community was reduced from 31 to 5 species (e.g. 32 ± 1 g m⁻² to 23 ± 2 g m⁻²) due mainly to a decline in the endogeic worm species Allolobophora rosea which was the most abundant of nine earthworm species observed (nearly half of all worms in each plot). However, no changes in the relative contribution of individual species or the three main earthworm ecological groups (anecies, endogeics, epigeics) to the entire earthworm community were observed with declining number of plant species. The responses of earthworm communities to plant species' loss appear to reflect changes in community fine root biomass in the topsoil (e.g. declining worm biomass with declining fine root biomass) observed in parallel studies conducted at this site. Further the results of this study demonstrate that a loss of plant species' from these calcareous grassland communities may also alter the age structure of earthworm communities, but not significantly influence their diversity or composition. Our data also indicate that rising atmospheric CO₂ may not greatly impact the size and composition of worm communities or alter the effects of plant species' loss on earthworm communities. Therefore, the disappearance of plant species from these native grasslands, as a result of ever increasing human activities, may be expected to lead to reductions in the size of earthworm communities and the ecosystem services they provide.