Tree litter is a key basal resource in temperate deciduous woodlands and streams that drain them. Litter decomposition promotes carbon and nutrient cycling, fueling woodland food webs. Research to date has not thoroughly explored how ongoing environmental changes affect this process. This study used microcosm and field experiments to investigate how multiple stressors (urban pollution, elevated atmospheric CO2 and stream acidification) affected litter chemical composition, invertebrate consumption, and terrestrial and aquatic mass loss. Leaf litter chemical composition differed between ambient- and elevated-CO2 litters, and between rural and urban litters, but the direction of these responses was complex and differed between experiments. In microcosms, leaf litter consumption by terrestrial and aquatic invertebrate detritivores was species-specific. After exposure to a woodland floor or headwater streams, urban litter broke down faster than rural litter, while CO2 treatment did little to influence mass loss. The abundance, richness and diversity of terrestrial and aquatic invertebrates associated with leaf litter generally declined from 28 to 112 days in the field. Taxon richness and diversity were generally higher in elevated- than ambient-CO2 leaf litter through time, while urban leaf litter had greater diversity than rural litter after 112 days only. Abundance was greater in the circumneutral than the acid stream. Aside from leaf litter, small woody debris was also affected by CO2 treatment: elevated-CO2 twigs had a greater concentration of nitrogen and lignin, and broke down faster than ambient-CO2 twigs on a woodland floor and in headwater streams. This work highlights the complexity of invertebrate- and ecosystem-scale responses to the effects of multiple environmental stressors, with implications for nutrient cycling and food webs. Urban pollution may have a greater influence on litter chemical composition than CO2 treatment, while effects of growth condition may be more important than stream acidity in influencing decay and invertebrate communities.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:633546 |
| Date | January 2014 |
| Creators | Dray, Matthew William |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/68365/ |
Page generated in 0.0013 seconds