Nitrogen dynamics in arctic tundra soils of varying age: differential responses to fertilization and warming Journal Article

Authors: Yano, Yuriko; Shaver, Gaius R.; Rastetter, Edward B.; Giblin, Anne E.; Laundre, James A.
Article Title: Nitrogen dynamics in arctic tundra soils of varying age: differential responses to fertilization and warming
Abstract: In the foothills of the Brooks Range, Alaska, different glaciation histories have created landscapes with varying soil age. Productivity of most of these landscapes is generally N limited, but varies widely, as do plant species composition and soil properties (e.g., pH). We hypothesized that the projected changes in productivity and vegetation composition under a warmer climate might be mediated through differential changes in N availability across soil age. We compared readily available [water-soluble NH4 (+), NO3 (-), and amino acids (AA)], moderately available (soluble proteins), hydrolyzable, and total N pools across three tussock-tundra landscapes with soil ages ranging from 11.5k to 300k years. The effects of fertilization and warming on these N pools were also compared for the two younger sites. Readily available N was highest at the oldest site, and AA accounted for 80-89 % of this N. At the youngest site, inorganic N constituted the majority (80-97 %) of total readily available N. This variation reflected the large differences in plant functional group composition and soil chemical properties. Long-term (8-16 years) fertilization increased the soluble inorganic N by 20- to 100-fold at the intermediate-age site, but only by twofold to threefold at the youngest site. Warming caused small and inconsistent changes in the soil C:N ratio and AA, but only in soils beneath Eriophorum vaginatum, the dominant tussock-forming sedge. These differential responses suggest that the ecological consequences of warmer climates on these tundra ecosystems are more complex than simply elevated N-mineralization rates, and that the responses of landscapes might be impacted by soil age, or time since deglaciation.
Keywords: PROTEINS; PROTEIN; AMINO-ACIDS; carbon storage; TERRESTRIAL ECOSYSTEMS; SPECIES; RICHNESS; NORTHERN ALASKA; LITTER DECOMPOSITION; organic nitrogen; amino acids; DIFFERENT GLACIAL HISTORIES; NONACIDIC TUNDRA; Available nitrogen; Hydrolyzable nitrogen; Plant community composition
Journal Title: Oecologia
Volume: 173
Issue: 4
ISSN: 0029-8549
Publisher: Springer Verlag  
Publication Place: NEW YORK; 233 SPRING ST, NEW YORK, NY 10013 USA
Date Published: 2013
Start Page: 1575
End Page: 1586
Notes: PT: J; TC: 0; UT: WOS:000328210000038