Incident radiation and the allocation of nitrogen within Arctic plant canopies: implications for predicting gross primary productivity

TitleIncident radiation and the allocation of nitrogen within Arctic plant canopies: implications for predicting gross primary productivity
Publication TypeJournal Article
Year of Publication2012
AuthorsStreet L.E, Shaver GR, Rastetter E.B, van Wijk M.T, Kaye B.A, Williams M.
JournalGlobal Change BiologyGlobal Change Biology
Date PublishedSep
ISBN Number1354-1013
Accession NumberISI:000307222700015
Keywordsair-temperature, c-3 plants, carbon balance, carbon-exchange, climate change, co2 flux, diffuse radiation, economics spectrum, gross primary production, leaf-area index, leaves, light extinction, nitrogen extinction, photosynthesis, specific leaf area, tundra, tundra vegetation, vegetation

Arctic vegetation is characterized by high spatial variability in plant functional type (PFT) composition and gross primary productivity (P). Despite this variability, the two main drivers of P in sub-Arctic tundra are leaf area index (LT) and total foliar nitrogen (NT). LT and NT have been shown to be tightly coupled across PFTs in sub-Arctic tundra vegetation, which simplifies up-scaling by allowing quantification of the main drivers of P from remotely sensed LT. Our objective was to test the LTNT relationship across multiple Arctic latitudes and to assess LT as a predictor of P for the pan-Arctic. Including PFT-specific parameters in models of LTNT coupling provided only incremental improvements in model fit, but significant improvements were gained from including site-specific parameters. The degree of curvature in the LTNT relationship, controlled by a fitted canopy nitrogen extinction co-efficient, was negatively related to average levels of diffuse radiation at a site. This is consistent with theoretical predictions of more uniform vertical canopy N distributions under diffuse light conditions. Higher latitude sites had higher average leaf N content by mass (NM), and we show for the first time that LTNT coupling is achieved across latitudes via canopy-scale trade-offs between NM and leaf mass per unit leaf area (LM). Site-specific parameters provided small but significant improvements in models of P based on LT and moss cover. Our results suggest that differences in LTNT coupling between sites could be used to improve pan-Arctic models of P and we provide unique evidence that prevailing radiation conditions can significantly affect N allocation over regional scales.

Alternate JournalGlobal Change Biol