Spatial Variability in Light Yields Colimitation of Primary Production by Both Light and Nutrients in a Forested Stream Ecosystem
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Colimitation of primary production is increasingly recognized as a dominant process across aquatic and terrestrial ecosystems. In streams, both nutrient availability and light availability have been shown to independently limit primary production, but colimitation by both light and nutrients is rarely considered. We used a series of nutrient-diffusing substrates (NDS) bioassays deployed across a range of light availability conditions in a single-study stream over two summers to determine the light level at which the limiting factor for benthic periphyton accrual transitioned from light to nutrients. Stream periphyton accrual was nutrient-limited in high-light patches, and light-limited in low-light patches, with the transition from being predominantly light-limited to being predominantly nutrient-limited occurring when daily light fluxes exceeded 3.5 mol m−2 day−1. We quantified light at each NDS bioassay location and at 5 m intervals throughout our two adjacent 160 m study reaches—one in structurally complex old-growth riparian forest and one bordered by more uniform second-growth forest. Although both reaches were colimited overall, the resource (light or nutrients) dominating limitation differed between the two riparian forest age/structure conditions. In the old-growth section, about three quarters of the reach was predominantly nutrient-limited, whereas in the second-growth reach only about a quarter of the streambed was nutrient-limited. In this stream, colimitation of benthic periphyton accrual by light and nutrients at the reach scale was an emergent property of the ecosystem that manifested as a result of high heterogeneity in riparian forest structure.
Keywordsnutrient-diffusing substrate nitrogen limitation light limitation colimitation benthic primary production HJ Andrews riparian forest stream light habitat heterogeneity
We thank Brian VerWey, Emily Heaston, Katherine Pospisil, and Chris Kopet for help in the field and in the lab. We thank Brian VerWey and Lindsey Thurman for feedback on early drafts of the manuscript. Summer 2015 fieldwork was supported by NSF DEB 1547628 awarded to DRW. SMC was supported by an NSF Postdoctoral Research Fellowship in Biology (DBI 1401954). Funding for author EMP was provided through the HJ Andrews Research Experience for Undergraduates (REU) program, and facilities were provided by the HJ Andrews Experimental Forest research program—both funded by the National Science Foundation’s Long-Term Ecological Research Program (DEB 1440409), US Forest Service Pacific Northwest Research Station, and Oregon State University.
- Bernot MJ, Sobota DJ, Hall RO, Mulholland PJ, Dodds WK, Webster JR, Tank JL, Ashkenas LR, Cooper LW, Dahm CN, Gregory SV, Grimm NB, Hamilton SK, Johnson SL, Mcdowell WH, Meyer JL, Peterson B, Poole GC, Valett HM, Arango C, Beaulieu JJ, Burgin AJ, Crenshaw C, Helton AM, Johnson L, Merriam J, Niederlehner BR, O’Brien JM, Potter JD, Sheibley RW, Thomas SM, Wilson K. 2010. Inter-regional comparison of land-use effects on stream metabolism. Freshw Biol 55:1874–90.CrossRefGoogle Scholar
- Fay PA, Prober SM, Harpole WS, Knops JMH, Bakker JD, Borer ET, Lind EM, MacDougall AS, Seabloom EW, Wragg PD, Adler PB, Blumenthal DM, Buckley Y, Chu CJ, Cleland EE, Collins SL, Davies KF, Du GZ, Feng XH, Firn J, Gruner DS, Hagenah N, Hautier Y, Heckman RW, Jin VL, Kirkman KP, Klein J, Ladwig LM, Li Q, McCulley RL, Melbourne BA, Mitchell CE, Moore JL, Morgan JW, Risch AC, Schutz M, Stevens CJ, Wedin DA, Yang LH. 2015. Grassland productivity limited by multiple nutrients. Nat Plants 1:15080. doi: 10.1038/nplants.2015.80.
- Franklin JF, Spies TA, Van Pelt R, Carey AB, Thornburgh DA, Berg DR, Lindenmayer DB, Harmon ME, Keeton WS, Shaw DC, Bible K, Chen JQ. 2002. Disturbances and structural development of natural forest ecosystems with silvicultural implications, using Douglas-fir forests as an example. For Ecol Manag 155:399–423.CrossRefGoogle Scholar
- Hill WR, Fanta SE. 2008. Phosphorus and light colimit periphyton growth at subsaturating irradiances. Freshw Biol 53:215–25.Google Scholar
- Hill WR, Roberts BJ, Francoeur SN, Fanta SE. 2011. Resource synergy in stream periphyton communities. J Ecol 99:454–63.Google Scholar
- R Core Team. 2014. R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org/.
- Roberts BJ, Mulholland PJ. 2007. In-stream biotic control on nutrient biogeochemistry in a forested stream, West Fork of Walker Branch. J Geophys Res 112:G04002. doi: 10.1029/2007JG000422.
- Tank JL, Bernot MJ, Rosi-Marshall EJ. 2007. Nitrogen limitation and uptake. In: Hauer FR, Lamberti GA, Eds. Methods in stream ecology. 2nd edn. Burlington: Elsevier.Google Scholar
- Vitousek PM, Aber JD, Howarth RW, Likens GE, Matson PA, Schindler DW, Schlesinger WH, Tilman D. 1997. Human alteration of the global nitrogen cycle: sources and consequences. Ecol Appl 7:737–50.Google Scholar