Litter Quality Modulates Effects of Dissolved Nitrogen on Leaf Decomposition by Stream Microbial Communities
Rates of leaf litter decomposition in streams are strongly influenced both by inorganic nutrients dissolved in stream water and by litter traits such as lignin, nitrogen (N) and phosphorus (P) concentrations. As a result, decomposition rates of different leaf species can show contrasting responses to stream nutrient enrichment resulting from human activities. It is unclear, however, whether the root cause of such discrepancies in field observations is the interspecific variation in either litter nutrient or litter lignin concentrations. To address this question, we conducted a controlled laboratory experiment with a known fungal community to determine decomposition rates of 38 leaf species exhibiting contrasting litter traits (N, P and lignin concentrations), which were exposed to 8 levels of dissolved N concentrations representative of field conditions across European streams (0.07 to 8.96 mg N L−1). The effect of N enrichment on decomposition rate was modelled using Monod kinetics to quantify N effects across litter species. Lignin concentration was the most important litter trait determining decomposition rates and their response to N enrichment. In particular, increasing dissolved N supply from 0.1 to 3.0 mg N L−1 accelerated the decomposition of lignin-poor litter (e.g. < 10% of lignin, 2.9× increase ± 1.4 SD, n = 14) more strongly than that of litter rich in lignin (e.g. > 15% of lignin, 1.4× increase ± 0.2 SD, n = 9). Litter nutrient concentrations were less important, with a slight positive effect of P on decomposition rates and no effect of litter N. These results indicate that shifts in riparian vegetation towards species characterized by high litter lignin concentrations could alleviate the stimulation of C turnover by stream nutrient enrichment.
KeywordsLitter breakdown Nutrient enrichment Freshwater fungi Litter lignin Michaelis–Menten–Monod kinetics Litter traits
The authors are grateful to Frédéric Julien and Wendy Amblas for litter CNP analyses.
This study is part of the FunctionalStreams project funded by the French National Research Agency (grant ANR-14-CE01-0009-01).
- 1.Chapin FS Jr, Matson PA, Mooney HA (2002) Principles of terrestrial ecosystem ecology. Springer-Verlag, New YorkGoogle Scholar
- 4.Tank JL, Rosi-Marshall EJ, Griffiths NA, Entrekin SA, Stephen ML (2010) A review of allochthonous organic matter dynamics and metabolism in streams. Freshw Sci 29:118–146Google Scholar
- 26.Hatakka A, Hammel KE (2010) Fungal biodegradation of lignocelluloses. In: Hofrichter M (ed) Industrial applications. The Mycota, vol 10. Springer, Berlin, pp 319–340Google Scholar
- 33.Suberkropp K, Arsuffi TL, Anderson JP (1983) Comparison of degradative ability, enzymatic activity, and palatability of aquatic hyphomycetes grown on leaf litter. Appl Environ Microbiol 46:237–244Google Scholar
- 34.Core Team R (2016) R: a language and environment for statistical computing. R Foundation for Statistical Computing, ViennaGoogle Scholar
- 35.Woodward G, Gessner MO, Giller PS, Gulis V, Hladyz S, Lecerf A, Malmqvist B, McKie B, Tiegs SD, Cariss H, Dobson M, Elosegi A, Ferreira V, Graça MAS, Fleituch T, Lacoursière JO, Nistorescu M, Pozo J, Risnoveanu G, Schindler M, Vadineanu A, Vought LB-M, Chauvet E (2012) Continental-scale effects of nutrient pollution on stream ecosystem functioning. Science 336:1438–1440CrossRefGoogle Scholar
- 36.Jabiol J, Cornut J, Tlili A, Gessner MO (2018) Interactive effects of dissolved nitrogen, phosphorus and litter chemistry on stream fungal decomposers. FEMS Microbiol Ecol 94(10). https://doi.org/10.1093/femsec/fiy151
- 44.Manning DWP, Rosemond AD, Gulis V, Benstead JP, Kominoski JS (2018) Nutrients and temperature additively increase stream microbial respiration. Glob Change Biol 24:e233–e247Google Scholar
- 45.Boyero L, Graça MAS, Tonin AM, Pérez J, Swafford AJ, Ferreira V, Landeira-Dabarca A, Alexandrou MA, Gessner MO, McKie BG, Albariño RJ, Barmuta LA, Callisto M, Chará J, Chauvet E, Colón-Gaud C, Dudgeon D, Encalada AC, Figueroa R, Flecker AS, Fleituch T, Frainer A, Gonçalves Jr JF, Helson JE, Iwata T, Mathooko J, M’Erimba C, Pringle CM, Ramírez A, Swan CM, Yule CM, Pearson RG (2017) Riparian plant litter quality increases with latitude. Sci Rep 7:1–10CrossRefGoogle Scholar
- 50.Tuchman NC, Wetzel RG, Rier ST, Wahtera KA, Teeri JA (2002) Elevated atmospheric CO2 lowers leaf litter nutritional quality for stream ecosystem food webs. Glob Change Biol 8:163–170Google Scholar