title: Canopy nitrogen, carbon assimilation, and albedo in temperate and boreal forests: Functional relations and potential climate feedbacks.
abstract: The availability of nitrogen represents a key constraint on carbon cycling in terrestrial ecosystems, and it is largely in this capacity that the role of N in the Earth's climate system has been considered. Despite this, few studies have included continuous variation in plant N status as a driver of broad-scale carbon cycle analyses. This is partly because of uncertainties in how leaf-level physiological relationships scale to whole ecosystems and because methods for regional to continental detection of plant N concentrations have yet to be developed. Here, we show that ecosystem CO(2) uptake capacity in temperate and boreal forests scales directly with whole-canopy N concentrations, mirroring a leaf-level trend that has been observed for woody plants worldwide. We further show that both CO(2) uptake capacity and canopy N concentration are strongly and positively correlated with shortwave surface albedo. These results suggest that N plays an additional, and overlooked, role in the climate system via its influence on vegetation reflectivity and shortwave surface energy exchange. We also demonstrate that much of the spatial variation in canopy N can be detected by using broad-band satellite sensors, offering a means through which these findings can be applied toward improved application of coupled carbon cycle-climate models.
authors.affiliation: Complex Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA. scott.ollinger@unh.edu
authors.forename: S V
authors.initials: SV
authors.lastname: Ollinger
authors.forename: A D
authors.initials: AD
authors.lastname: Richardson
authors.forename: M E
authors.initials: ME
authors.lastname: Martin
authors.forename: D Y
authors.initials: DY
authors.lastname: Hollinger
authors.forename: S E
authors.initials: SE
authors.lastname: Frolking
authors.forename: P B
authors.initials: PB
authors.lastname: Reich
authors.forename: L C
authors.initials: LC
authors.lastname: Plourde
authors.forename: G G
authors.initials: GG
authors.lastname: Katul
authors.forename: J W
authors.initials: JW
authors.lastname: Munger
authors.forename: R
authors.initials: R
authors.lastname: Oren
authors.forename: M-L
authors.initials: ML
authors.lastname: Smith
authors.forename: K T
authors.initials: KT
authors.lastname: Paw U
authors.forename: P V
authors.initials: PV
authors.lastname: Bolstad
authors.forename: B D
authors.initials: BD
authors.lastname: Cook
authors.forename: M C
authors.initials: MC
authors.lastname: Day
authors.forename: T A
authors.initials: TA
authors.lastname: Martin
authors.forename: R K
authors.initials: RK
authors.lastname: Monson
authors.forename: H P
authors.initials: HP
authors.lastname: Schmid
mesh_terms: D002244:Carbon / Q000378:metabolism*; D002980:Climate; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods; D005246:Feedback; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D018531:Spacecraft; D013696:Temperature; D014197:Trees / Q000378:metabolism*
chemical_list: D002244:Carbon; D009584:Nitrogen