Effects of elevated CO2 on litter chemistry and subsequent invertebrate detritivore feeding responses.
Elevated atmospheric CO2 can change foliar tissue chemistry. This alters leaf litter palatability to macroinvertebrate detritivores with consequences for decomposition, nutrient turnover, and food-web structure. Currently there is no consensus on the link between CO2 enrichment, litter chemistry, and macroinvertebrate-mediated leaf decomposition. To identify any unifying mechanisms, we presented eight invertebrate species from aquatic and terrestrial ecosystems with litter from Alnus glutinosa (common alder) or Betula pendula (silver birch) trees propagated under ambient (380 ppm) or elevated (ambient +200 ppm) CO2 concentrations. Alder litter was largely unaffected by CO2 enrichment, but birch litter from leaves grown under elevated CO2 had reduced nitrogen concentrations and greater C/N ratios. Invertebrates were provided individually with either (i) two litter discs, one of each CO2 treatment ('choice'), or (ii) one litter disc of each CO2 treatment alone ('no-choice'). Consumption was recorded. Only Odontocerum albicorne showed a feeding preference in the choice test, consuming more ambient- than elevated-CO2 birch litter. Species' responses to alder were highly idiosyncratic in the no-choice test: Gammarus pulex and O. albicorne consumed more elevated-CO2 than ambient-CO2 litter, indicating compensatory feeding, while Oniscus asellus consumed more of the ambient-CO2 litter. No species responded to CO2 treatment when fed birch litter. Overall, these results show how elevated atmospheric CO2 can alter litter chemistry, affecting invertebrate feeding behaviour in species-specific ways. The data highlight the need for greater species-level information when predicting changes to detrital processing-a key ecosystem function-under atmospheric change.
Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom.
Matthew W
MW
Dray
Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom ; School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, United States of America.
Thomas W
TW
Crowther
Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom.
Stephen M
SM
Thomas
Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom.
A Donald
AD
A'Bear
Institute of Forest Ecology, University of Natural Resources and Life Sciences (BOKU), Vienna, Austria.
Douglas L
DL
Godbold
Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom.
Steve J
SJ
Ormerod
York Environmental Sustainability Institute, University of York, York, United Kingdom.
Susan E
SE
Hartley
Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom.
T Hefin
TH
Jones
D000704:Analysis of Variance; D000818:Animals; D002245:Carbon Dioxide / Q000737:chemistry* / Q000378:metabolism*; D017753:Ecosystem; D060434:Herbivory; D007448:Invertebrates / Q000502:physiology*; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D010944:Plants / Q000378:metabolism*
D002245:Carbon Dioxide