Riparian forest composition affects stream litter decomposition despite similar microbial and invertebrate communities

• Published in: Ecology (Durham) Vol. 92; no. 1; pp. 151 - 159
• Main Authors: Kominoski, John S., Marczak, Laurie B., Richardson, John S.
• Format: Journal Article
• Language: English
• Published: Washington, DC Ecological Society of America 01-01-2011
• Subjects: alleles; Alnus rubra; Animal and plant ecology; Animal, plant and microbial ecology; Animals; aquatic invertebrates; Bacteria - metabolism; Biodegradation, Environmental; Biodiversity; Biological and medical sciences; biomass; canopy; coastal rainforest ecosystems; coniferous; Coniferous forests; Creeks & streams; deciduous; decomposition; Ecosystem; ecosystems; energy flow; Forest canopy; Forest ecosystems; Forest litter; forest trees; Forestry; Fundamental and applied biological sciences. Psychology; fungi; General aspects; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; Invertebrata; Invertebrates; Invertebrates - physiology; Lotic systems; metabolism; microbial; microbial communities; mixed canopy; Nutrients; organic matter; Plant litter; rain forests; restriction fragment length polymorphism; Riparian forests; Rivers; stream; Streams; subsidies; Terrestrial ecosystems; Trees; trophic relationships; Tsuga heterophylla; British Columbia; British Columbia Canada; Canada, British Columbia; Rain forest; Decomposition; Alnus rubra; Biodiversity; coniferous; Riparian; Dicotyledones; Ecosystem; Angiospermae; Gymnospermae; Stream; Tsuga heterophylla; Betulaceae; Microbial community; Composition; Litter; deciduous; microbial; coastal rainforest ecosystems; mixed canopy; Spermatophyta; Coniferales; Microorganism; Invertebrata; invertebrates; Canopy(vegetation)
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/10-0028.1

Cross-boundary flows of energy and nutrients link biodiversity and functioning in adjacent ecosystems. The composition of forest tree species can affect the structure and functioning of stream ecosystems due to physical and chemical attributes, as well as changes in terrestrial resource subsidies. We examined how variation in riparian canopy composition (coniferous, deciduous, mixed) affects adjacent trophic levels (invertebrate and microbial consumers) and decomposition of organic matter in small, coastal rainforest streams in southwestern British Columbia. Breakdown rates of higher-quality red alder (
Alnus rubra
) litter were faster in streams with a greater percentage of deciduous than coniferous riparian canopy, whereas breakdown rates of lower-quality western hemlock (
Tsuga heterophylla
) litter were independent of riparian forest composition. When invertebrates were excluded using fine mesh, breakdown rates of both litter species were an order of magnitude less and were not significantly affected by riparian forest composition. Stream invertebrate and microbial communities were similar among riparian forest composition, with most variation attributed to leaf litter species. Invertebrate taxa richness and shredder biomass were higher in
A. rubra
litter; however, taxa evenness was greatest for
T. heterophylla
litter and both litter species in coniferous streams. Microbial community diversity (determined from terminal restriction fragment length polymorphisms) was unaffected by riparian forest or litter species. Fungal allele richness was higher than bacterial allele richness, and microbial communities associated with lower-quality
T. heterophylla
litter had higher diversity (allele uniqueness and richness) than those associated with higher-quality
A. rubra
litter. Percent variation in breakdown rates was mostly attributed to riparian forest composition in the presence of invertebrates and microbes; however, stream consumer biodiversity at adjacent trophic levels did not explain these patterns. Riparian and stream ecosystems and their biotic communities are linked through exchange and decomposition of detrital resources, and we provide evidence that riparian forest composition affects stream ecosystem catabolism despite similarities in microbial and invertebrate communities.