Decline in Ecosystem δ¹³C and Mid-Successional Nitrogen Loss in a Two-Century Postglacial Chronosequence

• Main Authors: Malone, ET, Abbott, BW, Klaar, MJ, Kidd, C, Sebilo, M, Milner, AM, Pinay, G
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Nature 2018
• Subjects: Glacier Bay; glacier; Alaska
• Online Access: https://eprints.whiterose.ac.uk/129135/; https://eprints.whiterose.ac.uk/129135/24/noy020.pdf; https://eprints.whiterose.ac.uk/129135/10/Malone%20et%20al%202018_Supplemental%20Info%20Final.pdf

Uncertainty about controls on long-term carbon (C) and nitrogen (N) balance, turnover, and isotopic composition currently limits our ability to predict ecosystem response to disturbance and landscape change. We used a two-century, postglacial chronosequence in Glacier Bay, Alaska, to explore the influence of C and N dynamics on soil and leaf stable isotopes. C dynamics were closely linked to soil hydrology, with increasing soil water retention during ecosystem development resulting in a linear decrease in foliar and soil δ¹³C, independent of shifts in vegetation cover and despite constant precipitation across sites. N dynamics responded to interactions among soil development, vegetation type, microbial activity, and topography. Contrary to the predictions of nutrient retention theory, potential nitrification and denitrification were high, relative to inorganic N stocks, from the beginning of the chronosequence, and gaseous and hydrological N losses were highest at mid-successional sites, 140–165 years since deglaciation. Though leaching of dissolved N is considered the predominant pathway of N loss at high latitudes, we found that gaseous N loss was more tightly correlated with δ¹⁵N enrichment. These results suggest that δ¹³C in leaves and soil can depend as much on soil development and associated water availability as on climate and that N availability and export depend on interactions between physical and biological state factors.