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Endogenous and exogenous control of ecosystem function: N cycling in headwater streams

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dc.contributor.authorValett, H. M.en
dc.contributor.authorThomas, S. A.en
dc.contributor.authorMulholland, P. J.en
dc.contributor.authorWebster, Jackson R.en
dc.contributor.authorDahm, C. N.en
dc.contributor.authorFellows, C. S.en
dc.contributor.authorCrenshaw, C. L.en
dc.contributor.authorPeterson, C. G.en
dc.contributor.departmentBiological Sciencesen
dc.date.accessed2014-01-08en
dc.date.accessioned2014-01-10T20:07:56Zen
dc.date.available2014-01-10T20:07:56Zen
dc.date.issued2008-12en
dc.description.abstractAllochthonous inputs act as resource subsidies to many ecosystems, where they exert strong influences on metabolism and material cycling. At the same time, metabolic theory proposes endogenous thermal control independent of resource supply. To address the relative importance of exogenous and endogenous influences, we quantified spatial and temporal variation in ecosystem metabolism and nitrogen (N) uptake using seasonal releases of (15)N as nitrate in six streams differing in riparian-stream interaction and metabolic character. Nitrate removal was quantified using a nutrient spiraling approach based on measurements of downstream decline in (15)N flux. Respiration (R) and gross primary production (GPP) were measured with whole-stream diel oxygen budgets. Uptake and metabolism metrics were addressed as z scores relative to site means to assess temporal variation. In open-canopied streams, areal uptake (U; mu g N.m(-2).s(-1)) was closely related to GPP, metabolic rates increased with temperature, and R was accurately predicted by metabolic scaling relationships. In forested streams, N spiraling was not related to GPP; instead, uptake velocity (v(f); mm/s) was closely related to R. In contrast to open-canopied streams, N uptake and metabolic activity were negatively correlated to temperature and poorly described by scaling laws. We contend that streams differ along a gradient of exogenous and endogenous control that relates to the relative influences of resource subsidies and in-stream energetics as determinants of seasonal patterns of metabolism and N cycling. Our research suggests that temporal variation in the propagation of ecological influence between adjacent systems generates phases when ecosystems are alternatively characterized as endogenously and exogenously controlled.en
dc.identifier.citationH. M. Valett, S. A. Thomas, P. J. Mulholland, J. R. Webster, C. N. Dahm, C. S. Fellows, C. L. Crenshaw, and C. G. Peterson 2008. ENDOGENOUS AND EXOGENOUS CONTROL OF ECOSYSTEM FUNCTION: N CYCLING IN HEADWATER STREAMS. Ecology 89:3515–3527. http://dx.doi.org/10.1890/07-1003.1en
dc.identifier.doihttps://doi.org/10.1890/07-1003.1en
dc.identifier.issn0012-9658en
dc.identifier.urihttp://hdl.handle.net/10919/24805en
dc.identifier.urlhttp://www.esajournals.org/doi/pdf/10.1890/07-1003.1en
dc.language.isoen_USen
dc.publisherEcological Society of Americaen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectendogenousen
dc.subjectexogenousen
dc.subjectmetabolic theoryen
dc.subjectNitrogen uptakeen
dc.subjectprimaryen
dc.subjectproductionen
dc.subjectrespirationen
dc.subjectspatial subsidiesen
dc.subjectstreamsen
dc.subjecttemporal variationen
dc.subjectuptake lengthen
dc.subjectuptake velocityen
dc.subjectorganic-carbonen
dc.subjectcontinental-shelfen
dc.subjectnutrient-uptakeen
dc.subjectenergy-flowen
dc.subjectmetabolismen
dc.subjectstoichiometryen
dc.subjectNitrogenen
dc.subjectforesten
dc.subjectvariabilityen
dc.subjectdynamicsen
dc.subjectEnvironmental Sciences & Ecologyen
dc.titleEndogenous and exogenous control of ecosystem function: N cycling in headwater streamsen
dc.title.serialEcologyen
dc.typeArticle - Refereeden

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